Technical Service Training
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Technical Service Training
Diesel Injection and Engine Management Systems
Common Rail Systems
CG 8258/S en 01/2008 TC304 3 060H
To the best of our knowledge, the illustrations, technical information, data and descriptions in this issue were correct at the time of going to print. The right to change prices, specifications, equipment and maintenance instructions at any time without notice is reserved as part of FORD policy of continuous development and improvement for the benefit of our customers. No part of this publication may be reproduced, stored in a data processing system or transmitted in any form, electronic, mechanical, photocopy, recording, translation or by any other means without prior permission of Ford-Werke GmbH. No liability can be accepted for any inaccuracies in this publication, although every possible care has been taken to make it as complete and accurate as possible. Copyright ©2008
Ford-Werke GmbH Service training programs D-F/GT1 (GB)
Preface
More stringent exhaust and noise emission standards and calls for lower fuel consumption continue to place new demands on the fuel injection and engine management systems of diesel engines. In order to satisfy these requirements, the injection system must inject the fuel at high pressure into the combustion chamber to provide good mixture preparation and, at the same time, meter the injected fuel quantity with the highest possible accuracy. The common rail system offers good potential for development, which is of particular significance both now and in the future. By separating the pressure generation process from the injection process, the optimum injection pressure is always available for the injection process, regardless of engine speed. Modern engine management systems ensure that the fuel injection timing and injected fuel quantity are exactly calculated and delivered to the engine cylinders by the fuel injectors. The following common rail systems are currently installed in Ford vehicles: –
Bosch common rail system,
–
Siemens common rail system,
–
Denso common rail system.
Another big step towards achieving cleanliness in diesel engines is the newly developed diesel particulate filter system. This system helps reduce micro-fine diesel particulates by up to 99%. Completion of the eLearning program "Diesel Fuel Injection and Engine Management Systems" is a prerequisite for the study of this Student Information. This Student Information is divided into lessons. At the end of each lesson there is a set of test questions that are designed to monitor the student's progress. The solutions to these test questions can be found at the end of the Student Information.
Please remember that our training literature has been prepared for FORD TRAINING PURPOSES only. Repairs and adjustments MUST always be carried out according to the instructions and specifications in the workshop literature. Please make full use of the training offered by Ford Technical Training Courses to gain extensive knowledge of both theory and practice.
Service Training (G1008812)
1
Table of Contents
PAGE
Preface...............................................................................................................................
1
Lesson 1 – General Information Overview of the systems...................................................................................................................................................
6
Introduction.......................................................................................................................................................................
10
Injection characteristics.....................................................................................................................................................
11
Torque................................................................................................................................................................................
13
Emission Standard IV with or without DPF......................................................................................................................
13
Cleanliness when working on the common rail system....................................................................................................
13
Test questions................................................................................................................................................
14
Lesson 2 – Fuel System Overview...........................................................................................................................................................................
15
Low-pressure system....................................................................................................................................
20
General..............................................................................................................................................................................
20
Bosch common rail system...........................................................................................................................
21
Fuel filter...........................................................................................................................................................................
21
Overview of the high-pressure system..............................................................................................................................
25
Fuel pump..........................................................................................................................................................................
27
Fuel rail (common rail)......................................................................................................................................................
33
High-pressure fuel lines.....................................................................................................................................................
33
Fuel injectors (general)......................................................................................................................................................
33
Solenoid valve-controlled fuel injectors............................................................................................................................
34
Piezo-controlled fuel injectors...........................................................................................................................................
37
Siemens common rail system.......................................................................................................................
42
Fuel filter...........................................................................................................................................................................
42
Overview of the high-pressure system..............................................................................................................................
43
Fuel pump..........................................................................................................................................................................
44
Fuel rail and high-pressure fuel lines................................................................................................................................
47
Fuel injectors.....................................................................................................................................................................
48
Denso common rail system...........................................................................................................................
53
Fuel filter...........................................................................................................................................................................
53
Overview of the high-pressure system..............................................................................................................................
54
Fuel pump..........................................................................................................................................................................
55
Fuel rail and high-pressure fuel lines................................................................................................................................
58
Fuel injectors.....................................................................................................................................................................
60
Test questions................................................................................................................................................
62
2
Service Training
Table of Contents
Lesson 3 – Powertrain Control Module (PCM) General..............................................................................................................................................................................
63
Input signals......................................................................................................................................................................
63
Output signals....................................................................................................................................................................
63
Diagnosis...........................................................................................................................................................................
64
PCM and peripherals...................................................................................................................................
65
Bosch common rail system................................................................................................................................................
65
Siemens common rail system............................................................................................................................................
69
Denso common rail system...............................................................................................................................................
73
Strategies.......................................................................................................................................................
75
Idle speed control..............................................................................................................................................................
75
Fuel metering calculations.................................................................................................................................................
75
Smooth-running control (cylinder balancing)...................................................................................................................
77
External intervention into the injected fuel quantity.........................................................................................................
77
Controlling fuel injection..................................................................................................................................................
78
Controlling the fuel pressure.............................................................................................................................................
79
EGR system.......................................................................................................................................................................
81
Boost pressure control.......................................................................................................................................................
83
EOBD.............................................................................................................................................................
86
General..............................................................................................................................................................................
86
Fault logging and storing...................................................................................................................................................
87
Test questions................................................................................................................................................
88
Lesson 4 – Sensors Introduction.......................................................................................................................................................................
89
CKP sensor........................................................................................................................................................................
89
CMP sensor.......................................................................................................................................................................
91
MAP sensor.......................................................................................................................................................................
92
IAT sensor..........................................................................................................................................................................
93
MAPT sensor.....................................................................................................................................................................
93
BARO sensor.....................................................................................................................................................................
94
ECT sensor........................................................................................................................................................................
94
CHT sensor (Kent and Puma diesel engines only)............................................................................................................
96
Combined IAT sensor and MAF sensor............................................................................................................................
98
HO2S.................................................................................................................................................................................
99
Turbocharger position sensor (certain versions only).......................................................................................................
100
Vehicle speed signal..........................................................................................................................................................
101
APP sensor........................................................................................................................................................................
102
Service Training
3
Table of Contents
Fuel temperature sensor.....................................................................................................................................................
103
Fuel pressure sensor..........................................................................................................................................................
104
Engine oil level sensor (2.4L/3.2L Duratorq-TDCi (Puma) diesel engine)......................................................................
105
Engine oil level sensor (2.2L Duratorq-TDCi (DW) diesel engine).................................................................................
107
Oil pressure switch............................................................................................................................................................
109
Stoplamp switch/BPP switch.............................................................................................................................................
109
CPP switch........................................................................................................................................................................
110
Test questions................................................................................................................................................
111
Lesson 5 – Actuators Fuel metering valve...........................................................................................................................................................
112
Fuel pressure regulator......................................................................................................................................................
114
Fuel injectors (solenoid valve-controlled).........................................................................................................................
116
Fuel injectors (piezo-controlled).......................................................................................................................................
118
EGR valve.........................................................................................................................................................................
119
Wastegate control valve (vacuum-controlled systems).....................................................................................................
121
Intake manifold flap and intake manifold flap solenoid valve (vacuum-controlled systems)...........................................
122
Intake manifold flap actuator motor (1.6L Duratorq-TDCi (DV) diesel engine, Emission Standard IV)........................
123
Turbocharger variable vane electrical actuator..................................................................................................................
125
Electric fuel pump (2.2L Duratorq-TDCi (DW) diesel engine only)................................................................................
128
Test questions................................................................................................................................................
129
Lesson 6 – Engine Emission Control Introduction...................................................................................................................................................
130
Pollutant emissions reduction............................................................................................................................................
130
DPF (general)....................................................................................................................................................................
130
Regeneration of the DPF (general)....................................................................................................................................
131
DPF with fuel additive system.....................................................................................................................
133
Component overview.........................................................................................................................................................
133
DPF....................................................................................................................................................................................
135
Charge air cooler bypass...................................................................................................................................................
136
Fuel additive system – general..........................................................................................................................................
138
Components of the fuel additive system...........................................................................................................................
139
Component overview – system control.............................................................................................................................
141
PCM...................................................................................................................................................................................
143
Fuel additive control unit...................................................................................................................................................
143
Fuel additive pump unit.....................................................................................................................................................
144
Tank flap switch................................................................................................................................................................
145
Exhaust gas temperature sensor(s)....................................................................................................................................
146
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Service Training
Table of Contents
DPF differential pressure sensor ......................................................................................................................................
147
Intake manifold flap actuator motors (Bosch system only)..............................................................................................
148
Charge air cooler bypass flap actuator motor (Bosch system only)..................................................................................
148
Intake manifold flap and charge air cooler bypass flap solenoid valves (Siemens system)..............................................
150
Coated diesel particulate filter (DPF).........................................................................................................
151
Overview of the DPF.........................................................................................................................................................
151
Passive regeneration..........................................................................................................................................................
151
Active regeneration............................................................................................................................................................
152
Notes on the oil change interval........................................................................................................................................
152
DPF regeneration indicator (2006.5 Transit only).............................................................................................................
153
Intake manifold flap..........................................................................................................................................................
153
Components of the engine emission control system.........................................................................................................
154
Exhaust gas temperature sensor(s)....................................................................................................................................
155
DPF differential pressure sensor ......................................................................................................................................
155
Intake manifold flap position sensor (vacuum-controlled systems)..................................................................................
156
Intake manifold flap unit...................................................................................................................................................
157
Fuel vaporiser system...................................................................................................................................
158
General..............................................................................................................................................................................
158
Fuel vaporiser system fuel pump.......................................................................................................................................
159
Fuel vaporiser....................................................................................................................................................................
160
Test questions................................................................................................................................................
161
Answers to the test questions...........................................................................................
162
List of Abbreviations........................................................................................................
163
Service Training
5
Lesson 1 – General Information
Overview of the systems Bosch common rail system with "solenoid valve-controlled" fuel injectors
E51104
6
(G1009902)
Service Training
Lesson 1 – General Information
Bosch common rail system with "piezo-controlled" fuel injectors
E96077
Service Training (G1009902)
7
Lesson 1 – General Information
Siemens common rail system
E53583
8
(G1009902)
Service Training
Lesson 1 – General Information
Denso common rail system
E69955
Assignment of the common rail systems to the engines Engine 1.4L Duratorq-TDCi (DV) diesel 1.6L Duratorq-TDCi (DV) diesel 1.8L Duratorq-TDCi (Kent) diesel
Service Training (G1009902)
Bosch
Siemens X
Denso
X X*
9
Lesson 1 – General Information
Engine 2.0L Duratorq-TDCi (DW) diesel 2.2L Duratorq-TDCi (DW) diesel 2.2L Duratorq-TDCi (Puma) diesel 2.4L Duratorq-TDCi (Puma) diesel 3.2L Duratorq-TDCi (Puma) diesel
Bosch
Siemens X
Denso
X X* X* X
* Older versions are equipped with the Delphi common rail system. The Delphi common rail system is not part of this Student Information.
Introduction Increasingly higher demands are being placed on modern diesel engines. The focus today is not only on exhaust emissions but also on increasing environmental awareness and the demand for increasingly better economy and enhanced driving comfort. This requires the use of complex injection systems, high injection pressures and accurate fuel metering by fully electronically-controlled systems. The high injection pressures convert the fuel, via the injector nozzle, into tiny droplets, which, again due to the high pressure, can then be optimally distributed in the combustion chamber. This results in less unburned HC (Hydrocarbon), less CO (Carbon Monoxide) and fewer diesel exhaust particulates being produced in the subsequent combustion stage. In addition, the optimised mixture formation reduces fuel consumption. Diesel knock caused by the combustion process of an engine with direct injection is significantly reduced by means of additional pilot injection. NOX (Oxides Of Nitrogen) emissions can also be reduced by using this method. In particular, the demands placed upon the injection system and its regulation are as follows for modern diesel engines: • high injection pressures,
• values for injected fuel quantity, start of injection and boost pressure adapted to every operating condition, • load-independent idle speed control, • closed-loop EGR (Exhaust Gas Recirculation), • low injection timing and injected fuel quantity tolerances and high degree of precision over the entire service life, • possibility of interaction with other systems such as stability assist, PATS (Passive Anti-Theft System), • comprehensive diagnostic facilities, • substitute strategies in the event of faults. The common rail injection system has a large range of features to meet these demands. In common rail injection systems, pressure generation is separate from the injection process. The injection pressure is generated independently of engine speed and injected fuel quantity. The common rail injection system consists of a high-pressure pump and a fuel rail (fuel accumulator/rail). This fuel rail offers constant pressure for distributing fuel to the electrically-controlled fuel injectors. With this type of diesel injection or engine management, the driver has no direct influence on the injected fuel quantity. For example, there is no mechanical connection
• shaping of injection timing characteristics, • multiple injections,
10
(G1009902)
Service Training
Lesson 1 – General Information
between the accelerator pedal and the injection pump. The injected fuel quantity is determined by various parameters. These include: • driver demand (accelerator pedal position),
Simple main injection Needle lift of the fuel injector nozzle and pressure curve in a cylinder without pilot injection
• operating condition, • engine temperature, • effects on exhaust emissions, • prevention of engine and transmission damage,
1
• faults in the system. Using these parameters, the injected fuel quantity is calculated in the PCM (Powertrain Control Module) and fuel injection timing and injection pressure can be varied. The fuel is metered fully electronically by the PCM. The fully electronic diesel engine management system features a comprehensive fail-safe concept (integrated in the PCM software). It detects any deviations and malfunctions and initiates corresponding actions depending on the resulting effects (e.g. limiting the power output by reducing the quantity of fuel).
3
4
2
5
E64973
1
Combustion pressure in the cylinder
2
Needle lift
3
TDC (Top Dead Center)
Injection characteristics
4
Needle lift with simple main injection
As already mentioned at the beginning of the lesson, the exhaust emissions and fuel consumption of an engine are of great significance. These factors can only be minimised through precise operation of the injection system and comprehensive engine management strategies.
5
Crankshaft angle
In the case of diesel engines with a distributor-type fuel injection pump (e.g. in the Transit 2000.5), fuel injection takes place via simple main injection.
Consequently, the following requirements must be met by the common rail system:
The fuel is then injected mechanically into the combustion chamber by the injector nozzles in two seamlessly integrated stages (two-spring nozzle carrier principle).
• The injection timing must be exact. Even small variations have a significant effect on fuel consumption, exhaust emissions and combustion noise.
In the pressure curve, the combustion pressure increases only slightly in the phase before TDC corresponding to compression, but increases very sharply at the start of combustion.
• The fuel injection pressure is independently adapted to all operating conditions.
The sharp pressure rise intensifies the combustion noise.
• Injection must be reliably terminated. Calculation of the injected fuel quantity and the injection timing is precisely adapted to the mechanical components of the injection system. Uncontrolled fuel dribble (e.g. caused by a defective fuel injector) results in increased exhaust emissions and increased fuel consumption.
Service Training (G1009902)
11
Lesson 1 – General Information
Pilot injection Needle lift of the fuel injector nozzle and pressure curve in a cylinder with pilot injection
Note: As pressure generation and injection are separate in common rail systems, it is possible to considerably enhance the range for pilot injection. This has led to a significant improvement in the running smoothness of the engine. With modern fuel injectors, it is also possible to work with multiple pilot injections. The greater the number of pilot injections, the lower the noise emissions.
Post-injection (vehicles with DPF (Diesel Particulate Filter) system)
1 3
Needle lift of the injector nozzle with pilot and post-injection 4
5
2
2
5
4
1
6
6
E64974
3
1
Combustion pressure in the cylinder
2
Needle lift
3
TDC
4
Needle lift with pilot injection
5
Needle lift with main injection
1
Needle lift
6
Crankshaft angle
2
Pilot injection
3
Crankshaft angle
4
Main injection
5
Advanced post-injection
6
Retarded post-injection
E51105
In the case of vehicles with a common rail injection system, electrically-controlled pilot injection occurs after a set time prior to the main injection event. Pilot injection means that a small amount of fuel is injected into the cylinder prior to the main injection. The small pilot-injection fuel quantity is ignited, heats up the upper part of the cylinder and thereby brings it into an optimum temperature range (preconditioning of the combustion chamber). This means that the main injection mixture ignites more quickly and the rise in temperature and combustion pressure is less abrupt as a result. Advantage: • Continuous build-up of combustion pressure, resulting in reduced combustion noise. • Reduction of oxides of nitrogen in the exhaust gas.
12
For vehicles with a DPF (Diesel Particulate Filter) system, two post-injections are employed during the regeneration process, in addition to the pilot and main injections, depending on the requirements. Advanced post-injection is initiated in certain load/speed ranges immediately after main injection. Fuel is then injected during the on-going combustion. The main purpose of this advanced post-injection is to raise the exhaust gas temperature during the regeneration process of the DPF. In addition, some of the diesel particulates produced during regeneration are after-burned.
(G1009902)
Service Training
Lesson 1 – General Information
Retarded post-injection only occurs shortly before BDC (Bottom Dead Center) and also serves to raise the exhaust gas temperature. In contrast to advanced post-injection, during retarded post-injection the fuel is not burned, but vaporises due to the residual heat in the exhaust gas. This exhaust/fuel mixture is delivered to the exhaust system by the exhaust stroke. In the oxidation catalytic converter, the fuel vapour reacts with the residual oxygen (above a certain temperature) and burns. This provides sustained heating of the oxidation catalytic converter, which supports the regeneration of the DPF.
Torque In general, diesel engines generate a high torque across a wide engine speed range. This is achieved through uniformly good cylinder charging (working without a throttle plate) and high combustion pressure.
Overtorque function On some vehicle versions, an overtorque function (also called an overboost function) is used. This makes it possible to briefly exceed the maximum specified torque during rapid acceleration (by about 15 to 35 Nm depending on the calibration). The short-term torque increase is an advantage when overtaking, for example.
Measures for the reduction of exhaust emissions inside the engine include, for example: • further optimised exhaust gas recirculation by means of an electrically-controlled EGR system with intake air restriction, • optimisation of the combustion chamber design and the injection characteristics. In addition to the internal engine measures, the second method employs a DPF system. The use of the DPF reduces diesel particulate emissions by up to 99%. This reduction far exceeds the requirements for the European emission limits of Emission Standard IV. It can therefore be deduced that the use of the DPF will be of great importance with regard to future emission standards, but is not absolutely necessary for meeting Emission Standard IV.
Cleanliness when working on the common rail system NOTE: Because the components of the high-pressure fuel system are high-precision machined parts, it is essential that scrupulous cleanliness is observed when carrying out any work on the system. In this regard, refer to the instructions in the current Service Literature.
The vehicle acceleration is calculated based on the vehicle speed signal and the CKP (Crankshaft Position) sensor. During acceleration, the PCM activates the overtorque function in an engine speed range between 1,700 and 3,500 rpm.
Emission Standard IV with or without DPF At the time of going to press, Emission Standard IV applies in Europe. In the diesel sector, Emission Standard IV is achieved using two different methods. One method consists of reducing exhaust emissions by means of internal engine measures to the extent that the prescribed limits are met.
Service Training (G1009902)
13
Test questions
Lesson 1 – General Information
Tick the correct answer or fill in the gaps. 1. What is the advantage of the common rail system? a. The high injection pressures reduce combustion temperatures; exhaust gas recirculation is not required. b. Pressure generation and injection are separated. c. The injection pressure is generated as a function of engine speed. d. Combustion noise is substantially reduced as a result of indirect injection.
2. What is the effect of pilot injection? a. Pilot injection results in an abrupt build-up of combustion pressure and therefore reduced combustion noise. b. Pilot injection results in an abrupt build-up of combustion pressure and therefore increased combustion noise. c. Pilot injection results in a gradual increase in combustion pressure. d. Pilot injection only results in a reduction of fuel consumption.
3. Where are post-injections utilised? a. In vehicles with an electric EGR system. b. In vehicles with an NOX catalytic converter. c. In vehicles without a diesel particulate filter system. d. In vehicles with a diesel particulate filter system.
4. The overtorque function a. prevents abrupt deceleration when the accelerator pedal is suddenly released at high vehicle speeds. b. makes it possible to briefly exceed the maximum specified torque when starting the vehicle on a gradient. c. makes it possible to briefly exceed the maximum specified torque during rapid acceleration. d. is activated in response to certain malfunctions in the engine management system.
14
(G1009903)
Service Training
Lesson 2 – Fuel System
Overview Bosch common rail system with "solenoid valve-controlled" fuel injectors
3 2 1 D C
E
B A
F
5 6
4
G
7 8
E51106
A
Fuel line
G
Fuel return to the fuel tank
B
Run-off line for excess delivered fuel
1
Fuel pump
C
High-pressure line
2
Fuel rail (common rail)
D
Fuel injection line
3
Fuel injector
E
Fuel return from the fuel pump
4
Fuel temperature sensor
F
Leak-off pipe
5
Fuel return collector pipe
Service Training (G1009904)
15
Lesson 2 – Fuel System
6
Fuel filter
7
Fuel tank
8
Fuel pump and sender unit
Bosch common rail system with "piezo-controlled" fuel injectors
2
1
B C
4
3
5 A D
F
8 E
6 7 E96088
A
Fuel return from the fuel pump
F
Fuel line
B
High-pressure line
1
Fuel pump
C
Fuel injection line
2
Fuel rail
D
Leak-off pipe
3
Fuel injector
E
Fuel return to the fuel tank
4
Back pressure valve
16
(G1009904)
Service Training
Lesson 2 – Fuel System
5
Return gateway
7
Fuel pump and sender unit
6
Fuel tank
8
Fuel filter
Siemens common rail system
3 2 1 C B
D
A
E 4
5
6
F
8
7
E53588
A
Fuel line
F
Fuel return to the fuel tank
B
High-pressure line
1
Fuel pump
C
Fuel injection line
2
Fuel rail (common rail)
D
Fuel return from the fuel pump
3
Fuel injector
E
Leak-off pipe
4
Fuel return collector pipe
Service Training (G1009904)
17
Lesson 2 – Fuel System
5
Fuel temperature sensor
7
Fuel tank
6
Fuel filter
8
Fuel pump and sender unit
Denso common rail system
1
2 B C
3
4
5 A D
F
8 E
6 7 E69808
A
Fuel return from the fuel pump
F
Fuel line
B
High-pressure line
1
Fuel pump
C
Fuel injection line
2
Fuel rail (common rail)
D
Leak-off pipe
3
Fuel injector
E
Fuel return to the fuel tank
4
Pressure relief valve
18
(G1009904)
Service Training
Lesson 2 – Fuel System
5
T-piece
7
Fuel pump and sender unit
6
Fuel tank
8
Fuel filter
Service Training (G1009904)
19
Low-pressure system
Lesson 2 – Fuel System
General Function Fuel is drawn from the fuel tank through the fuel filter by the transfer pump which is integrated in the fuel pump. The fuel pump compresses the fuel and forces it into the fuel rail. The fuel pressure required for any given situation is available for the fuel injectors for each injection process. Leak-off fuel from the fuel injectors and/or returning fuel from the fuel pump is fed back into the fuel tank.
Possible causes of faults in fuel lines and the fuel tank Fuel lines may be blocked due to foreign bodies or bending. In addition, blocked parts and lines of the low-pressure system can cause air to get into the low-pressure system on account of the increased vacuum in the system. Air can also enter the low-pressure system through loose or leaking line connections. Faulty valves or lines in the tank ventilation system can impair the flow of fuel through the low-pressure system.
Effects of faults (low-pressure system contains air or is blocked) Poor engine starting when warm or cold. Irregular idling. Engine will not start. Engine starts, but cuts out again immediately afterwards. Engine has insufficient power. Note: At a certain residual fuel amount, the PCM causes the engine to judder. The intention is to draw the driver's attention to the fact that the vehicle must urgently be refuelled. Note for vehicles with EOBD: If the PCM causes the engine to judder because the fuel tank is empty, the EOBD (European On-Board Diagnostics) are deactivated during this phase. This prevents apparent faults from being displayed.
20
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
Fuel filter
15
1
30
3
System with solenoid valve-controlled fuel injectors
4 1
3
2 2
2
1
5 6
3
1
5
6 2
7 E51107
4
E43249
1
Fuel line to the fuel pump
2
Water drain screw
3
Electric fuel preheater
4
Fuel line connection with fuel tank
1
Battery junction box
2
Fuel preheater relay
3
Fuse (10A)
4
Fuse (15A)
5
Ground
6
Electric fuel preheater in the fuel filter
7
Ground
The electric bimetallically-controlled fuel preheater works independently of the PCM. It is actuated via a fuel preheater relay when the ignition is switched on (ignition ON). However, the activation of the heating element is dependent on the current temperature.
The fuel filter clipped onto the transaxle end of the cylinder head is equipped with an electric fuel heater.
Below a fuel temperature of 0 to –4 °C, the circuit is closed by the bimetal and the heating element thus energised.
There is a water drain screw in the top section of the filter housing for draining the filter.
The bimetal opens the circuit at a fuel temperature from 1 to 5 °C and ends the heating phase.
The fuel filter must be drained of water regularly in accordance with the service intervals.
Service Training (G1009904)
21
Bosch common rail system
Lesson 2 – Fuel System
System with piezo-controlled fuel injectors 2
3
1
4
5 7
6 E97401
1
Fuel return (to the fuel tank)
2
Fuel return line (from the fuel pump)
3
Fuel temperature sensor
4
Fuel line (to the fuel pump)
5
Fuel filter water drain screw
6
Water drain line
7
Fuel line (from the fuel tank)
The fuel filter is made of plastic. It is installed on the front side of the engine on the intake side. A security shield protects the fuel filter from damage in the event of a frontal impact. Located on the fuel filter housing is a water drain screw. The fuel filter must be drained via this screw in accordance with the service intervals. Note: • Before draining the fuel filter, make sure that the surrounding components do not come into contact with the fuel that is drained. There is a thermo valve integrated in the fuel filter for preheating the fuel.
22
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
How fuel preheating works
5
1 4 3
2 A
B
6
7
E96134
A
Fuel return temperature < 10 °C
4
Upper part of the fuel filter
B
Fuel return temperature > 20 °C
5
Fuel return line (from the fuel pump)
1
Fuel return line (to the fuel tank)
6
Thermostat open
2
Fuel return outlet
7
Thermostat closed
3
Bypass (to the fuel filter)
The fuel filter is equipped with a mechanical fuel preheater.
Fuel return temperature < 10 °C:
There is a spring-loaded thermo valve integrated in the fuel return in the upper part of the fuel filter. The thermo valve determines the quantity of fuel that is returned to the fuel tank or flows directly back into the fuel filter.
• The bypass to the fuel filter is wide open in this state. The cross section of the fuel return outlet is slightly open.
Service Training (G1009904)
• The thermo valve is in compressed state.
• The majority of the returning fuel flows through the wide open bypass into the fuel filter. Only a small part of the returning fuel can flow back to the fuel tank via the slightly open cross section of the fuel return outlet.
23
Bosch common rail system
Fuel return temperature > 20 °C: • The thermo valve expands against the spring force. • The bypass to the fuel filter is only slightly open in this state. The cross section of the fuel return outlet is now wide open. Fuel return temperature < 10 °C > 20 °C
Possible causes of faults
Lesson 2 – Fuel System
• The majority of the returning fuel flows through the wide open fuel return outlet. Only a small part of the returning fuel can flow through the slightly open bypass to the fuel filter.
Percentage of fuel to the fuel tank Percentage of fuel to the fuel filter 5 - 10 % 90 - 95 % 95 - 100 % 0-5% Irregular idling.
Fuel filters may be blocked by dirt. Air may also enter the low-pressure system as a result of leaks in the fuel filter.
Engine will not start. Engine starts, but cuts out again immediately afterwards. Engine has insufficient power.
Effects of faults Poor starting when the engine is warm or cold.
24
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
Overview of the high-pressure system System with "solenoid valve-controlled" fuel injectors
3
2
4 1 5
6
9
8
7
E51108
1
Fuel injector
6
High-pressure line
2
Fuel injection line
7
Fuel pump
3
Leak-off pipe
8
Fuel rail (common rail)
4
Fuel metering valve
9
Fuel pressure sensor
5
Transfer pump
Service Training (G1009904)
25
Bosch common rail system
Lesson 2 – Fuel System
System with "piezo-controlled" fuel injectors
1
2
3
5
4
11
6
7 8
9
10 E97421
1
Fuel injector
7
Fuel pressure control valve
2
Fuel pressure sensor
8
Fuel return
3
Fuel rail (common rail)
9
Fuel pump
4
Fuel injection line
10 Fuel line
5
High-pressure line
11 Set of leak-off pipes with back pressure valve *
6
Overpressure leakage line
* There is a back pressure valve in the set of leak-off pipes. This valve maintains a back pressure of approx. 10 bar in the leak-off pipe while the engine is running. The back pressure valve cannot be renewed separately during servicing.
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Service Training
Lesson 2 – Fuel System
Bosch common rail system
Fuel pump Overview CP3.2 fuel pump
2
3
4
5
1
6 E51109
1
Transfer pump
4
Eccentric
2
Fuel metering valve
5
Halfshaft
3
Pump plunger
6
Pump housing
Service Training (G1009904)
27
Bosch common rail system
Lesson 2 – Fuel System
Two different types of fuel pump are used in the Bosch common rail system:
CP1H fuel pump
• CP3.2 fuel pump and
1
• CP1H fuel pump. With the launch of the Focus C-MAX 2003.75 (06/2003-), initially only the CP3.2 was installed. Over time, the CP3.2 was increasingly replaced by the CP1H and this pump was installed from the outset for new launches.
5
2 3 4 E70770
1
Fuel metering valve
2
Fuel return connection
3
Fuel line connection
4
Transfer pump
5
High-pressure connection (to the fuel rail)
The following table shows the introduction dates for the CP1H based on the vehicle. Vehicle Fiesta 2002.25 (11/2001-) Focus C-MAX 2003.75 (06/2003-)/Focus 2004.75 (07/2004-) with 67 kW (90 PS) Focus C-MAX 2003.75 (06/2003-)/Focus 2004.75 (07/2004-) with 82 kW (110 PS) Mondeo 2007.5/S-MAX/ Galaxy 2006.5
Introduction of CP1H October 2004 February 2005
May 2005
With the start of production
The function of the CP1H fuel pump is essentially the same as that of the CP3.2.
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Service Training
Lesson 2 – Fuel System
Bosch common rail system
Flow of fuel through the fuel pump
F
G
B
C
6 3 E 5
A
D 1
2 4
7
8
9
E51111
A
To the fuel injectors
2
High-pressure part
B
High fuel pressure
3
Pressure restrictor
C
Flow of fuel through the fuel pump
4
Fuel metering valve
D
Return flow to the transfer pump
5
Overflow throttle valve
E
Fuel line
6
Fuel pump
F
Fuel injector leak-off
7
Transfer pump
G
Fuel return
8
Fuel filter
1
Fuel rail
9
Fuel tank
Service Training (G1009904)
29
Bosch common rail system
Lesson 2 – Fuel System
Transfer pump
The transfer pump is designed as a gear pump and delivers the required fuel to the fuel pump. Essential components are two counter-rotating, meshed gears that transport the fuel in the tooth gaps from the intake side to the delivery side.
2 1
3
The contact line of the gears forms a seal between the intake side and the delivery side and prevents the fuel from flowing back. The delivery quantity is approximately proportional to the engine speed. For this reason, fuel quantity control is required. E51110
1
Intake side
2
Drive gear
3
Delivery side
There is an overflow throttle valve incorporated in the fuel pump for fuel quantity control purposes.
Overflow throttle valve A 1
B 1
C 1
2
2
2
3
3
3
7
7
7
4 4
8
4 8
6
6
6 9
5
5
5
E51112
A
Low engine speeds
2
Time
B
Increasing engine speeds
3
Compression spring
C
High engine speeds
4
Restrictor
1
Transfer pump pressure
5
To the high-pressure chambers
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(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
6
Control piston
8
Fuel pump cooling bypass
7
Fuel pump lubrication/cooling/ventilation
9
Return bypass to the transfer pump
High-pressure generation (up to 1,800 bar) means high thermal load on the individual components of the fuel pump. The mechanical components of the fuel pump must also be sufficiently lubricated to ensure durability. The overflow throttle valve is designed to ensure optimum lubrication or cooling for all operating conditions. At low engine speeds (low transfer pump pressure), the control piston is moved only slightly out of its seat. The lubrication/cooling requirement is correspondingly low. A small amount of fuel is released to lubricate/cool the pump via the restrictor at the end of the control piston. NOTE: The fuel pump features automatic venting. Any air present in the fuel pump is vented through the restrictor.
With increasing engine speed (increasing transfer pump pressure), the control piston is moved further against the compression spring. Increasing engine speeds require increased cooling of the fuel pump. Above a certain pressure, the fuel pump cooling bypass is opened and the flow rate through the fuel pump is increased. At high engine speeds (high transfer pump pressure), the control piston is moved further against the compression spring. The fuel pump cooling bypass is now fully open (maximum cooling). Excess fuel is transferred to the intake side of the transfer pump via the return bypass. In this way, the internal pump pressure is limited to a maximum of 6 bar.
High-pressure generation
1 2 9
3
8 7
4
6
5
E51113
Service Training (G1009904)
31
Bosch common rail system
Lesson 2 – Fuel System
1
High pressure to the fuel rail
6
Eccentric cam
2
Exhaust valve
7
High-pressure chamber
3
Spring
8
Pump plunger
4
Fuel line
9
Intake valve
5
Halfshaft
The fuel pump is driven via the halfshaft. An eccentric element is fixed to the halfshaft and moves the three plungers up and down according to the shape of the cams on the eccentric element.
Zero delivery valve
Fuel pressure from the transfer pump is applied to the intake valve. If the transfer pressure exceeds the internal pressure of the high-pressure chamber (pump plunger in TDC position), the intake valve opens.
4 1
Fuel is now forced into the high-pressure chamber, which moves the pump plunger downwards (intake stroke).
2
If the BDC position of the pump plunger is exceeded, the intake valve closes due to the increasing pressure in the high-pressure chamber. The fuel in the high-pressure chamber can no longer escape.
E51114
As soon as the pressure in the high-pressure chamber exceeds the pressure in the fuel rail, the outlet valve opens and the fuel is forced into the fuel rail via the high-pressure connection (delivery stroke). The pump plunger delivers fuel until TDC is reached. The pressure then drops so that the outlet valve closes. As the pressure on the remaining fuel is reduced, the pump plunger moves downward. If the pressure in the high-pressure chamber falls below the transfer pressure, the intake valve reopens and the process starts again.
3
1
From the high-pressure chamber annular channel
2
Zero delivery valve
3
Calibrated bore (ø = 0.4 mm)
4
To the transfer pump
The zero delivery valve is located between the annular channel that is connected to the intake valves of the high-pressure chambers and the fuel metering valve. Even in the fully closed state, the fuel metering valve (see "Lesson 3 – Engine management system") is not completely sealed. In other words, a small amount of leakage still gets into the annular channel to the high-pressure chambers due to the transfer pump pressure. As a result, the intake valves are opened and an undesirable pressure increase may occur in the high-pressure system. To prevent this, the zero delivery valve features a calibrated bore. In this way, excess fuel is fed back to the intake side of the transfer pump.
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Service Training
Lesson 2 – Fuel System
Bosch common rail system
Fuel rail (common rail)
Fuel pressure sensor
Structure and purpose
There is a fuel pressure sensor located on the fuel rail so that the engine management system can precisely determine the injected fuel quantity as a function of the current fuel pressure in the fuel rail (see "Lesson 4 – Sensors").
1
High-pressure fuel lines
E43248
1
Fuel pressure sensor
The fuel rail is made of forged steel. The fuel rail performs the following functions: • stores fuel under high pressure and • minimises pressure fluctuations. Pressure fluctuations are induced in the high-pressure fuel system due to the operating movements in the high-pressure chambers of the fuel pump and the opening and closing of the solenoid valves on the fuel injectors. Consequently, the fuel rail is designed in such a way that, on the one hand, it possesses sufficient volume to minimise pressure fluctuations, but, on the other hand, the volume in the fuel rail is sufficiently low to build up the fuel pressure required for a quick start in the shortest possible time.
Function
E43246
NOTE: The bending radii are exactly matched to the system and must not be changed. NOTE: After disconnecting one or more high-pressure fuel lines, these must always be renewed. The reason for this is that leaks can occur when retightening due to distortion of the connections of the old lines. The high-pressure fuel lines connect the fuel pump to the fuel rail and the fuel rail to the individual fuel injectors.
Fuel injectors (general) Depending on the engine type, different fuel injectors are used:
The fuel supplied by the fuel pump passes through a high-pressure line to the high-pressure accumulator. The fuel is then sent to the individual fuel injectors via the four fuel injection lines which are all the same length.
• solenoid valve-controlled fuel injectors or
When fuel is taken from the fuel rail for an injection process, the pressure in the fuel rail remains almost constant.
Piezo-controlled fuel injectors are installed in the 2.2L Duratorq-TDCi (DW) diesel engine.
Service Training (G1009904)
• piezo-controlled fuel injectors. Solenoid valve-controlled fuel injectors are installed in the 1.6L Duratorq-TDCi (DV) diesel engine.
Start of injection and injected fuel quantity are controlled via the fuel injectors.
33
Bosch common rail system
Lesson 2 – Fuel System
The injection timing is calculated using the angle/time system in the PCM. The main input variables for this are the signals from the CKP and the CMP (Camshaft Position) sensors.
NOTE: The combustion chamber seals must not be reused. The exact procedure for the correct installation of the seals and the plastic rings can be found in the current Service Literature.
Solenoid valve-controlled fuel injectors
The fuel injectors are divided into different function blocks: • injector nozzle,
1
• hydraulic servo system, • solenoid valve.
2
7 3 4
6
5 E43245
1
Leak-off pipe connection
2
Retainer
3
Plastic ring
4
Seal
5
Combustion chamber seal
6
High-pressure fuel line connection
7
Solenoid valve connector
34
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
Function A
B
13
12
1 2
11
11
10
10
3 4
9
9
8
8
7
7
5
6
6
E51115
A
Fuel injector closed
6
Nozzle needle
B
Fuel injector open
7
Nozzle prechamber
1
Solenoid valve coil
8
Nozzle needle spring
2
Feed channel
9
Valve control piston
3
Valve ball
10 Valve control chamber
4
Feed restrictor
11 Outlet restrictor
5
Feed channel to the nozzle prechamber
Service Training (G1009904)
35
Bosch common rail system
12 Fuel return The fuel is fed from the high-pressure connection via a feed channel into the nozzle prechamber and via the feed restrictor into the valve control chamber. The valve control chamber is connected to the fuel return via the outlet restrictor, which can be opened by means of a solenoid valve.
Fuel injector closed In its closed state (solenoid valve de-energised), the outlet restrictor is closed by the valve ball so that no fuel can escape from the valve control chamber. In this state, the pressures in the nozzle prechamber and in the valve control chamber are the same (pressure balance). There is, however, also a spring force acting on the nozzle needle spring so that the nozzle needle remains closed (hydraulic pressure and spring force of the nozzle needle spring). No fuel can enter the combustion chamber.
Lesson 2 – Fuel System
13 Solenoid valve connector Note: The closing speed of the nozzle needle is determined by the flow rate at the feed restrictor. Injection terminates when the nozzle needle reaches its bottom stop.
Indirect actuation Indirect actuation of the nozzle needle via a hydraulic booster system is used because the forces required for rapid opening of the nozzle needle cannot be generated directly with the solenoid valve. The "control quantity" therefore required in addition to the injected fuel quantity enters the fuel return via the restrictors in the control chamber.
Leak-off quantities In addition to the control quantity, there are leak-off quantities at the nozzle needle and valve control piston guides. These leak-off quantities are also discharged into the fuel return.
Fuel injector opens Service instructions (fuel injector correction factor)
As soon as the hydraulic force in the valve control chamber falls below that of the nozzle prechamber and the nozzle needle spring, the nozzle needle opens. Fuel is now injected into the combustion chamber via the spray holes.
015
6
0
11
38415 1724 2809 13
5
760680
The outlet restrictor is opened via actuation of the solenoid valve. This lowers the pressure in the valve control chamber, as well as the hydraulic force on the valve control piston.
0 8 0 440 FO F DD 1
Fuel injector closes After a period determined by the PCM, the power supply to the solenoid valve is interrupted. This results in the outlet restrictor being closed again. By closing the outlet restrictor, pressure from the fuel rail builds up in the valve control chamber via the feed restrictor. This increased pressure exerts an increased force on the valve control piston. This force and the spring force of the nozzle needle spring now exceed the force in the nozzle prechamber and the nozzle needle closes.
36
2
E51116
1
Fuel injector
2
Correction factor
Inside the hydraulic servo system there are various restrictors with extremely small diameters which have specific manufacturing tolerances. These manufacturing tolerances are given as part of a correction factor which is located on the outside of the fuel injector.
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
To ensure optimum fuel metering, the PCM must be informed when a fuel injector is changed. Furthermore, after new PCM software has been loaded via the IDS (Integrated Diagnostic System), the fuel injectors must also be configured with this software. This is done by inputting the 8-digit correction factor (divided into two blocks of four on the fuel injector) into the PCM with the help of the IDS and taking into account the corresponding cylinder. Note: If the correction factors are not entered properly with the IDS, the following faults can occur:
• increased combustion noise, • engine will not start.
Effects of faulty fuel injector(s) (mechanical faults) Increased black smoke production. Fuel injector leaks. Increased combustion noise as a result of coked nozzle needles. Irregular idling.
• increased black smoke formation, • irregular idling,
Piezo-controlled fuel injectors 1
6
2 5 4 3
E96132
1
Fuel injector retaining bolt
4
Centring ring
2
Retaining clip centring pin
5
Fuel injector
3
Seal
6
Retaining clip
Service Training (G1009904)
37
Bosch common rail system
The fuel injectors are mounted on the cylinder head and protrude into the centre of the individual combustion chambers.
Lesson 2 – Fuel System
Function Structure of the piezo-controlled fuel injector
The fuel injectors are opened and closed using a piezo element. The piezo element is located inside the fuel injector.
a
b 6
The piezo-controlled fuel injectors switch around four times faster than solenoid valve-controlled fuel injectors. The results in the following advantages: • Multiple injections with flexible injection timing and intervals between the individual injections.
1
• Realisation of very small injected fuel quantities for the pilot injection(s).
2
• Low noise emissions (up to 3 dB). • Improved fuel economy (up to 3%).
3
• Lower exhaust emissions (up to 20%). • Increased engine power output (up to 7%).
4
• Improved running smoothness.
5 E97388
a
Fuel return
b
High-pressure connection
1
Piezo element
2
Hydraulic coupler
3
Control valve
4
Nozzle module with nozzle needle
5
Spray holes
6
Electrical connector
In the case of the piezo-controlled fuel injector, the nozzle needle is indirectly controlled via a control valve. 'Indirectly' means that the nozzle needle is opened and closed via a hydraulic circuit. The hydraulic circuit comprises a low-pressure and a high-pressure part. The control valve provides the interface between the high-pressure and the low-pressure parts. The required injected fuel quantity is controlled via the opening times of the control valve.
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Service Training
Lesson 2 – Fuel System
Bosch common rail system
Function of the control valve
B
A
C
1
2 6 3 4
5
a
c
b
E97392
A
Initial position
4
Feed restrictor
B
Nozzle needle opens
5
Nozzle needle
C
Nozzle needle closes
6
Bypass
1
Control valve
a
Fuel rail pressure
2
Outlet restrictor
b
Leak-off pressure
3
Control chamber
c
Control chamber pressure
Initial position • If the piezo element is not activated by the PCM, then the control valve is in the initial position. This means that the high-pressure part is closed off from the low-pressure part. • The fuel rail pressure plus the spring force is acting upon the nozzle needle. The fuel injector nozzle is closed (no injection).
• The pressure in the control chamber is reduced via the flow rate ratio of the outlet and feed restrictors. • The fuel rail pressure on the nozzle needle is now greater than the pressure in the control chamber and the spring force. The nozzle needle is lifted and injection begins.
Nozzle needle opens • When the piezo element is activated, the control valve opens and closes the bypass. • The pressure in the control chamber can then escape into the fuel return.
Service Training (G1009904)
39
Bosch common rail system
Lesson 2 – Fuel System
Nozzle needle closes • When the piezo element is discharged by the PCM, the control valve opens the bypass once more.
The fuel around the hydraulic coupler has a back pressure of approx. 10 bar. The back pressure valve is located in the leak-off pipe.
• The control chamber is then filled again via the feed and outlet restrictors. The control chamber pressure increases again rapidly via the bypass.
Piezo element not actuated:
• As soon as the control chamber pressure plus the spring force are once more greater than the fuel rail pressure on the nozzle needle, the nozzle needle closes and injection ends.
Piezo element actuated:
Hydraulic coupler
• In this state, the pressure in the hydraulic coupler is in balance with its surroundings (around 10 bar).
• The piezo element piston moves downwards. As a result, the pressure in the hydraulic coupler rises. A small amount of leakage flows from the hydraulic coupler into the low-pressure circuit of the fuel injector via the piston guide clearances. • The pressure increase in the hydraulic coupler causes downward movement of the control valve piston via the hydraulic cushion and injection starts.
1 2
3
6 5
Once the injection process is finished, the deficit in the coupler must be refilled. This is done in reverse via the guide clearances of the piston. The back pressure of around 10 bar is extremely important for the correct operation of the fuel injectors.
Service instructions (fuel injector correction factor) 4
E97396
1
Piezo element
2
Back pressure valve
3
Hydraulic coupler back pressure
4
Hydraulic coupler
5
Control valve piston
6
Piezo element piston
The hydraulic coupler fulfils the following functions: • Transmission and amplification of the piezo stroke. • Compensation of any play. • Termination of injection in the event of electrical disconnection of the fuel injector (e.g. if a cable breaks during the injection process). The hydraulic coupler is comparable to a hydraulic lash adjuster in terms of its function.
40
E96133
Inside the hydraulic servo system there are calibrated bores with extremely small diameters. These bores have specific manufacturing tolerances. Tolerances also arise when the mechanical, hydraulic and electrical components are combined. At the factory, each fuel injector is tested and then sorted into a specific category. The fuel injector is assigned a correction factor according to the category. The 10-digit correction factor is engraved on the head of the fuel injector (arrow).
(G1009904)
Service Training
Lesson 2 – Fuel System
Bosch common rail system
To ensure precise fuel metering, the PCM must be informed when an injector is changed. The correction factor is entered with the help of the IDS. When entering the number, make sure that the fuel injector is assigned to the correct cylinder.
Effects of faults Fuel injector(s) (mechanical faults): • increased black smoke production, • fuel injector leaks, • increased combustion noise as a result of coked nozzle needles.
Service Training (G1009904)
41
Siemens common rail system
Lesson 2 – Fuel System
Fuel filter
Fuel filter of the 2.0L Duratorq-TDCi (DW) diesel engine
Function Fuel filter of the 1.4L Duratorq-TDCi (DV) diesel engine
2
1
3
1 3
4 E43236
2 4
1
Fuel line connection (from the fuel tank)
2
Fuel feed connection (to the fuel pump)
3
Electric fuel preheater
4
Water drain screw
The fuel preheater is bimetallically-controlled and functions independently of the PCM.
5
The bimetallically-controlled fuel preheater is activated when the ignition is on (ignition key in position II) regardless of whether the engine is running or not. The bimetal closes the circuit as a function of the ambient temperature and the heating element in the fuel preheater is activated.
E53589
1
Fuel line connection (from the fuel tank)
2
Fuel line connection (to the fuel pump)
3
Fuel filter with water separator
4
Water drain screw
5
Electric fuel preheater
Different fuel filters are used for the Siemens common rail system depending on the type of engine. Their operating principles and service-relevant characteristics, however, are very similar. Both fuel filters are equipped with a water separator which must be drained regularly in accordance with the specified service intervals. Both fuel filters also feature a fuel preheater which is activated at low temperatures.
42
• For the 1.4L Duratorq-TDCi, the on/off temperature for the heating element is approximately 5 °C. • For the 2.0L Duratorq-TDCi (DW) diesel engine, the heating element is switched on at –2 °C ± 2 °C and switched off at +3 °C ± 2 °C.
Possible causes of faults Fuel filters may be blocked by dirt. Air may also enter the low-pressure system as a result of leaks in the fuel filter. Note: A certain quantity of air is drawn out of the fuel tank together with the fuel when the transfer pump draws fuel into the fuel pump. The air bubbles are very small, however, and cannot initially be seen with the naked eye. The small air bubbles are separated out in the fuel filter and clump together to form larger bubbles. These air bubbles occasionally emerge from the filter material
(G1009904)
Service Training
Lesson 2 – Fuel System
Siemens common rail system
and are drawn into the fuel pump. They can be seen through a transparent hose. This form of separation is entirely normal. The visual inspection for air bubbles in the transparent hose is therefore not counted as a fault diagnosis.
Effects of faults Poor starting when the engine is warm or cold. Irregular idling. Engine will not start. Engine starts, but cuts out again immediately afterwards. Engine has insufficient power.
Overview of the high-pressure system Illustration shows the high-pressure system of the 2.0L Duratorq-TDCi (DW) diesel engine
1 2
6
4
5
3
E43283
1
Fuel injector
4
Fuel pump
2
Fuel metering valve
5
Fuel rail
3
Fuel pressure control valve
6
Fuel pressure sensor
Service Training (G1009904)
43
Siemens common rail system
Lesson 2 – Fuel System
Fuel pump Overview Illustration shows the fuel pump with halfshaft for timing belt drive (1.4L Duratorq-TDCi (DV) diesel engine)
2
3
1
A 6
C B
5
4
E53590
A
Fuel return
3
Fuel pressure control valve
B
High-pressure connection
4
Eccentric
C
Fuel line
5
Halfshaft
1
Fuel metering valve (partial view)
6
Transfer pump
2
High-pressure pump element (displacement unit)
NOTE: The fuel metering valve as well as the fuel pressure control valve are part of the fuel pump and therefore must not be renewed separately during servicing.
44
Note: Depending on the engine version, the fuel pump is driven via the timing belt for camshaft drive (1.4L Duratorq-TDCi (DV) diesel engine) or via the exhaust camshaft (2.0L Duratorq-TDCi (DW) diesel engine). The design and function of the fuel pump are essentially similar.
(G1009904)
Service Training
Lesson 2 – Fuel System
Siemens common rail system
High-pressure generation and fuel routing in the fuel pump 2
1
4
5
3
B C 7
6
10 11 A D
13
8
9
14
10 11
13
13
10
11 12
E53591
A
Fuel line
4
Transfer pump
B
Fuel line (fuel quantity fed to the fuel pump)
5
Fuel metering valve
C
High-pressure connection to the fuel rail
6
Fuel pressure control valve
D
Fuel return
7
Filter
1
Admission-pressure control valve
8
Fuel pump
2
Strainer filter
9
Eccentric on the halfshaft
3
Intake side of the transfer pump
10 Pump element intake valve
Service Training (G1009904)
45
Siemens common rail system
Lesson 2 – Fuel System
11 Pump element outlet valve
13 High-pressure pump elements
12 High-pressure ring line
14 Lubrication valve
The fuel is drawn from the fuel tank via the fuel filter by means of the transfer pump integrated in the fuel pump.
The high-pressure chambers are formed by three pump elements (displacement units), each offset by 120 degrees.
The transfer pump delivers the fuel on to the fuel metering valve and to the lubrication valve. When the fuel metering valve is closed, the admission pressure control valve opens and routes the excess fuel back to the intake side of the transfer pump.
The fuel pressure control valve is located in the high-pressure channel, between the high-pressure chambers and the high-pressure outlet port to the fuel rail. This electromagnetically-operated valve which is actuated by the PCM controls the fuel pressure which is fed into the fuel rail via the high-pressure outlet port.
The lubrication valve is calibrated to always ensure sufficient lubrication and cooling in the interior of the pump.
The fuel pressure control valve routes the excess fuel into the fuel return line and back to the fuel tank.
The fuel quantity fed to the high-pressure chambers (pump elements) is determined via the electromagnetically-operated fuel metering valve (actuated by the PCM).
Principle of high-pressure generation (intake stroke) A
B
1
1 C
2
D
2
3
3 5
4 4
5
E53592
A
Fuel intake
2
Exhaust valve
B
Fuel delivery
3
Piston
C
Fuel feed from the fuel metering valve
4
Halfshaft
D
Fuel outlet port to the high-pressure ring line
5
Eccentric
1
Intake valve
The three pump plungers are actuated by the rotary movement of the fuel pump halfshaft and the eccentric on the shaft.
46
When the fuel metering valve opens the feed to the high-pressure chambers, the fuel pressure from the transfer pump is fed to the intake valves at the
(G1009904)
Service Training
Lesson 2 – Fuel System
Siemens common rail system
high-pressure chambers. If the transfer pressure exceeds the internal pressure of the high-pressure chamber (pump plunger in TDC position), the intake valve opens.
Fuel rail and high-pressure fuel lines
Fuel is now forced into the high-pressure chamber, which moves the pump plunger downwards (intake stroke).
Illustration shows the system in the 2.0L Duratorq-TDCi (DW) diesel engine
Fuel rail
1
Principle of high-pressure generation (delivery stroke) When the pump plunger passes BDC, the intake valve closes due to the increasing pressure in the high-pressure chamber. The fuel in the high-pressure chamber can no longer escape.
2
As soon as the pressure in the high-pressure chamber exceeds the pressure in the high-pressure channel, the exhaust valve opens and the fuel is forced into the high-pressure channel (delivery stroke). The pump plunger delivers fuel until TDC is reached. The pressure then drops and the exhaust valve closes. The pressure on the remaining fuel is reduced. The pump plunger moves downwards. If the pressure in the high-pressure chamber falls below the transfer pressure, the intake valve reopens and the process starts again.
Service instructions Specific versions only: After installing a new fuel pump, the adapted values of the fuel metering valve must be reset with the help of the IDS.
4 3 E53593
1
High pressure fuel lines (to the fuel injectors)
2
High-pressure fuel line (to the fuel pump)
3
Fuel rail
4
Fuel pressure sensor
The fuel rail is made of forged steel. The fuel rail performs the following functions: • stores fuel under high pressure and • minimises pressure fluctuations. Pressure fluctuations are induced in the high-pressure fuel system due to the operating movements in the high-pressure chambers of the fuel pump and the opening and closing of the fuel injectors. The fuel rail is therefore designed in such a way that its volume is sufficient, on the one hand, to minimise pressure fluctuations. On the other hand, the volume in the fuel rail is sufficiently low to build up the fuel pressure required for a quick start in the shortest possible time. The fuel supplied by the fuel pump flows via a high-pressure line to the fuel rail (high-pressure accumulator). The fuel is then sent to the individual fuel injectors via the four fuel injection lines which are all the same length.
Service Training (G1009904)
47
Siemens common rail system
Lesson 2 – Fuel System
When fuel is taken from the fuel rail for an injection process, the pressure in the fuel rail remains almost constant.
High-pressure fuel lines
Fuel pressure sensor
NOTE: After disconnecting one or more high-pressure fuel lines, these must always be renewed. The reason for this is that leaks can occur when retightening due to distortion of the connections of the old lines.
NOTE: The fuel pressure sensor must not be removed from the fuel rail during servicing. If the fuel pressure sensor is faulty, the fuel rail must be renewed along with the fuel pressure sensor. There is a fuel pressure sensor located on the fuel rail so that the engine management system can precisely determine the injected fuel quantity as a function of the current fuel pressure in the fuel rail (see also "Lesson 4 - Sensors").
NOTE: The bending radii are exactly matched to the system and must not be changed.
The high-pressure fuel lines connect the fuel pump to the fuel rail and the fuel rail to the individual fuel injectors.
Fuel injectors A
B
1
1 3
6
2
2 3
C
C 6
7
D 5 4
D
11
7
6
E 9 8
4 10
E
E53594
A
Fuel injector (1.4L Duratorq-TDCi (DV) diesel engine and 1.8L Duratorq-TDCi (Kent) diesel engine)
B
Fuel injector (2.0L Duratorq-TDCi (DW) diesel engine)
C
Fuel injector head
48
D
Hydraulic servo system
E
Fuel injector nozzle
1
Connector for PCM
2
Piezo actuator
3
High-pressure fuel line connection
4
Combustion chamber seal
(G1009904)
Service Training
Lesson 2 – Fuel System
Siemens common rail system
5
Emission standard coding
9
6
Fuel return connection
10 Adapter fastening clip
7
Retainer
11 Plastic bush
8
Fuel return adapter
Depending on the engine version, fuel injectors of different designs are used. Their basic construction and function are, however, largely the same. The start of injection and the injected fuel quantity specified by the PCM are implemented by means of the piezo-electrically-controlled fuel injectors. Depending on engine speed and engine load, the fuel injectors are actuated by the PCM with an opening voltage of approximately 70 V. The piezo effect causes the voltage within the piezo element to rise to approximately 140 V. The fuel injectors inject the appropriate fuel quantity per working cycle for all engine operating conditions into the combustion chambers. Extremely short switching times of approximately 200 µs permit extremely rapid reaction to changes in the operating conditions. The fuel quantity to be injected can thus be metered very precisely. The fuel injectors are divided into three assemblies:
O-ring
NOTE: The fuel injectors cannot be dismantled during repair as this results in their destruction. NOTE: The wiring harness connectors of the fuel injectors must on no account be unplugged when the engine is running. The piezo actuators remain expanded for a certain period after the power is cut off in the charging phase, i.e. the nozzles remain open. Effect: continuous injection and engine damage. The combustion chamber seals must be renewed during servicing.
Special features 1.4L Duratorq-TDCi (DV) diesel engine: • In newer versions, a distinction is made between Emission Standard III and Emission Standard IV fuel injectors. A code is stamped onto the fuel injector shaft for this purpose: – E3 = Emission Standard III, – E4 = Emission Standard IV.
• fuel injector head, including the piezo actuator,
2.0L Duratorq-TDCi (DW) diesel engine:
• hydraulic servo system,
• A guide bushing located in the lower part of the cylinder head and a plastic bushing on the fuel injector shaft serve to fasten the fuel injector.
• fuel injector nozzle.
Service Training (G1009904)
49
Siemens common rail system
Lesson 2 – Fuel System
How fuel injectors work Fuel injector closed
3
3 5
4
1
6 2 3
2 7
8
E53595
1
High-pressure feed
5
Mushroom valve
2
Control piston
6
Control chamber
3
Fuel return
7
Nozzle prechamber
4
Piezo actuator
8
Nozzle needle
The fuel is fed at high pressure from the fuel rail via the high-pressure feed into the control chamber and the nozzle prechamber. The piezo actuator is de-energised and the orifice to the fuel return is closed by means of the spring-loaded mushroom valve.
The hydraulic force now exerted on the nozzle needle by the high fuel pressure in the control chamber via the control piston is greater than the hydraulic force acting on the nozzle needle, as the surface of the control piston in the control chamber is greater than the surface of the nozzle needle in the nozzle prechamber. The nozzle needle of the fuel injector is closed (no injection).
50
(G1009904)
Service Training
Lesson 2 – Fuel System
Siemens common rail system
Fuel injector opens
9
3
5
4 1
6 2
9
3
2
8 7
E53596
1
High-pressure feed
6
Control chamber
2
Control piston
7
Nozzle prechamber
3
Fuel return
8
Nozzle needle
4
Piezo actuator
9
Valve piston
5
Mushroom valve
The piezo actuator which is energised by the PCM expands (charging phase) and pushes against the valve piston. The mushroom valve opens the orifice which connects the control chamber with the fuel return. This results in a pressure drop in the control chamber and the hydraulic force acting on the nozzle needle is now greater than the force acting on the control piston in the control chamber.
The piezo actuator is deactivated at a certain point determined by the PCM. The valve piston moves back upwards and the mushroom valve closes off the control chamber. As soon as the pressure in the control chamber exceeds the pressure in the nozzle prechamber, the nozzle needle closes off the spray holes and injection ends.
This causes the nozzle needle to be moved upwards, the fuel injector opens and the fuel enters the combustion chamber via the spray holes.
Service Training (G1009904)
51
Siemens common rail system
Fuel injector identification markings
Lesson 2 – Fuel System
• When installing one new fuel injector, it should be noted which classification is marked on the fuel injector. • All the fuel injectors installed in an engine must have the same classification. When installing all new fuel injectors, the new fuel injectors may have a different classification, For example, if the old fuel injectors are in class "5" and the new ones are all class "4", this is permissible. The change of classification must nevertheless be communicated to the PCM with the help of the IDS.
Effects of faulty fuel injector(s) (mechanical faults) Increased black smoke production. Fuel injector leaks. a
Increased combustion noise as a result of coked nozzle needles.
b
Irregular idling.
c
d
e
f
E53597
Identification number coding: a. Classification (2.0L Duratorq-TDCi (DW) diesel engine only) b. Ford part number c. Year of manufacture (C = 2003, D = 2004 . . . ) d. Month (A = January, B = February, . . . L = December) e. Day (01 ... 31) f. Part number (00001 ... 99999) The identification markings of the piezo fuel injectors are located on the fuel injector head. Classification (correction factor): • The fuel injectors of the 2.0L Duratorq-TDCi (DW) diesel engine are marked with a number for classification purposes. • A total of three classifications are available: – 4, 5 and 6
52
(G1009904)
Service Training
Lesson 2 – Fuel System
Denso common rail system
Fuel filter
Fuel preheating works via a bimetallically-controlled control valve. Fuel flow control only works at fuel temperatures between 15 and 45 ° C.
How fuel preheating works
Fuel temperature below 15 °C: 1
2 3
4
• The bimetallically-controlled control valve is fully open; a defined fuel return volume from the fuel pump is returned directly to the fuel filter via the control valve. Fuel temperature greater than 45 °C:
8
• The bimetallically-controlled control valve is fully closed; the full fuel return volume flows past the fuel filter into the fuel tank.
7
Fuel filter with water-in-fuel sensor (certain markets only)
5 6
E69908
1
Fuel return (to the fuel filter)
2
Fuel return (to the fuel tank)
3
Fuel line (to the fuel pump)
4
Fuel filter minder gauge
5
Water-in-fuel sensor (certain markets only)
6
Water drain screw
7
Water-in-fuel sensor wiring harness
8
Fuel line (from the fuel tank)
Service Training (G1009904)
After installing a new fuel filter, a parameter reset of the values for the water-in-fuel sensor must be carried out with the help of the IDS.
53
Denso common rail system
Lesson 2 – Fuel System
Overview of the high-pressure system Illustration shows the system in the 2.4L Duratorq-TDCi
E69809
1
High-pressure line
7
Fuel metering valve
2
Leak-off pipe
8
Fuel pressure sensor
3
Fuel injection line
9
Fuel temperature sensor
4
Fuel injector
10 Fuel pump
5
Pressure relief valve
11 Fuel return
6
Fuel rail (common rail)
54
(G1009904)
Service Training
Lesson 2 – Fuel System
Denso common rail system
Service instructions After all work on the high-pressure system, a fuel system leak test must be performed with the help of the IDS.
Fuel pump Illustration shows the fuel pump of the 2.4L Duratorq-TDCi
1
2
3 4
A
14 5 B 6 7 12 13
8
11 10
9
C E69909
A
High-pressure fuel to the fuel rail
7
Transfer pump (rotor pump)
B
Fuel return
8
Fuel intake
C
Fuel line
9
Fuel filter
1
High-pressure chamber exhaust valve
10 Eccentric cam ring
2
High-pressure chamber intake valve
11 Eccentric cam
3
Pump plunger
12 Halfshaft
4
Fuel metering valve return spring
13 Fuel tank
5
Fuel metering valve
14 Overflow throttle valve
6
Admission pressure control valve (pump interior pressure)
Service Training (G1009904)
55
Denso common rail system
Design The fuel pump provides the interface between the low-pressure and high-pressure systems. Its function is to always provide sufficient compressed fuel under all operating conditions and for the entire service life of the vehicle. Low-pressure part: • The transfer pump draws fuel out of the fuel tank via the fuel intake. • The pump internal pressure is adjusted via the admission pressure control valve. This ensures that sufficient lubrication and cooling are always provided for the fuel pump components. Excess fuel is transferred to the intake side of the transfer pump via the admission pressure control valve.
Lesson 2 – Fuel System
• A portion of the fuel is transferred to the fuel metering valve from the transfer pump. The fuel quantity delivered to the high pressure chambers is determined by the opening cross-section of the fuel metering valve. • The small restriction bore in the overflow throttle valve provides for automatic ventilation of the fuel pump. The entire low-pressure system is designed to allow a defined quantity of fuel to flow back into the fuel tank via the overflow throttle valve. This assists cooling of the fuel pump. High-pressure part: • A total of two high-pressure chambers, each with one pump plunger, are used for high-pressure generation. • The pump plungers are driven via an eccentric cam, which is in turn driven by the halfshaft (principle similar to the Bosch common rail system). • The fuel pump permanently generates the high system pressure for the fuel rail.
56
(G1009904)
Service Training
Lesson 2 – Fuel System
Denso common rail system
Principle of high-pressure generation
1
2
A
3
6 C 4
5 B
E69910
A
Pump plunger 1
3
Eccentric cam
B
Pump plunger 2
4
Eccentric cam ring
C
To the fuel rail
5
Fuel metering valve
1
Intake valve
6
Halfshaft
2
Exhaust valve
Service Training (G1009904)
57
Denso common rail system
The rotary movement of the halfshaft is converted to a reciprocating movement by the eccentric cam. The eccentric cam ring transfers the reciprocating movement to the pump plungers.
Lesson 2 – Fuel System
Fuel rail and high-pressure fuel lines Fuel rail 1
The pump plungers are arranged offset by 180 degrees. This means that during a reciprocating movement, pump plunger 1 performs exactly the opposite movement to pump plunger 2.
5
The eccentric cam generates an "upward" stroke: • Pump plunger 1 moves in the direction of TDC, thus pressurising the fuel and delivering it to the fuel rail via the exhaust valve. The intake valve is pressed into its seat by the delivery pressure. • Pump plunger 2 is moved by the tension spring force in the direction of BDC. Due to the high pressure in the fuel rail, the exhaust valve is pressed into its seat. The pump internal pressure opens the intake valve and fuel flows into the high-pressure chamber. The eccentric cam generates a "downward" stroke: • The process is the reverse to that previously described.
4
3
2
E98851
1
High-pressure fuel lines (to the fuel injectors)
2
Pressure relief valve
3
Fuel rail
4
Fuel pressure sensor
5
High-pressure fuel lines (to the fuel pump)
The fuel rail performs the following functions: • stores fuel under high pressure and
Programming the fuel pump (fuel metering valve)
• minimises pressure fluctuations.
After installing a new fuel pump/fuel metering valve and/or PCM, the fuel metering valve of the fuel pump must be programmed with the help of the IDS.
Pressure fluctuations are induced in the high-pressure fuel system due to the operating movements in the high-pressure chambers of the fuel pump and the opening and closing of the solenoid valves on the fuel injectors.
Service instructions After installing a new fuel pump or fuel metering valve, the fuel pump must be adapted with the help of the IDS.
Consequently, the fuel rail is designed in such a way that, on the one hand, it possesses sufficient volume to minimise pressure fluctuations, but, on the other hand, the volume in the fuel rail is sufficiently low to build up the fuel pressure required for a quick start in the shortest possible time. The fuel supplied by the fuel pump passes through a high-pressure line to the high-pressure accumulator. The fuel is then sent to the individual fuel injectors via the four fuel injection lines which are all the same length. When fuel is taken from the fuel rail for an injection process, the pressure in the fuel rail remains almost constant.
58
(G1009904)
Service Training
Lesson 2 – Fuel System
Denso common rail system
High-pressure fuel lines
Pressure relief valve
NOTE: The bending radii are exactly matched to the system and must not be changed.
The pressure relief valve opens at a fuel pressure of above 2,200 bar. It serves as a safeguard in the event of a malfunction in the high-pressure system. This prevents damage caused by excessive fuel pressure in the high-pressure system.
NOTE: After disconnecting one or more high-pressure fuel lines, these must always be renewed. The reason for this is that leaks can occur when retightening due to distortion of the connections of the old lines. The high-pressure fuel lines connect the fuel pump to the fuel rail and the fuel rail to the individual fuel injectors.
Fuel pressure sensor The fuel pressure sensor must not be renewed separately in the event of a fault. The whole fuel rail must always be renewed in the event of a fault.
Service Training (G1009904)
The pressure relief valve works as a disposable valve. This means that it must be renewed after it has been triggered once, as it will no longer seal properly. NOTE: The pressure relief valve cannot be renewed separately during servicing. The entire fuel rail must be renewed in the event of a fault. NOTE: Triggering of the pressure relief valve is frequently caused by a defective fuel metering valve. Any triggering of the pressure relief valve is detected by the PCM, which then sets an appropriate DTC (Diagnostic Trouble Code) and actuates the MIL (Malfunction Indicator Lamp).
59
Denso common rail system
Lesson 2 – Fuel System
Fuel injectors Design
1 2
10
11 3
4
9
8
5
7
6
E98372
1
Solenoid valve
7
Combustion chamber seal
2
Fuel rail pressure
8
Fuel rail pressure
3
Fuel strainer
9
Valve seat
4
Piston rod
10 Leak-off
5
Nozzle needle spring
11 Control chamber
6
Nozzle needle
NOTE: The combustion chamber seals must not be reused.
Start of injection and injected fuel quantity are adjusted via the fuel injectors.
The exact procedure for the correct installation of the fuel injectors can be found in the current Service Literature.
60
(G1009904)
Service Training
Lesson 2 – Fuel System
Denso common rail system
In order to achieve the optimal injection timing and precise injected fuel quantity, special fuel injectors with a hydraulic servo system and electrical actuator unit (solenoid valve) are used. The fuel injectors are actuated directly by the PCM.
After installing one or more new fuel injectors, the following service functions must be performed with the help of the IDS: • entry of the correction factors of the fuel injectors and
The PCM specifies the injected fuel quantity and the injection timing.
• adaptation of pilot injection by the fuel injectors.
The fuel injectors are divided into different function blocks:
Inside the hydraulic servo system there are various restrictors with extremely small diameters which have specific manufacturing tolerances.
• injector nozzle, • hydraulic servo system,
Entry of the correction factors:
These manufacturing tolerances are given as part of a correction factor, which is located on the housing of the fuel injector.
• solenoid valve.
Effects of faulty fuel injector(s) (mechanical faults)
To ensure optimum fuel metering, the PCM must be informed when a fuel injector is changed.
Increased black smoke production.
Furthermore, after new PCM software has been loaded via IDS, the fuel injectors must also be configured with this software.
Fuel injector leaks. Increased combustion noise as a result of coked nozzle needles. Irregular idling.
This is achieved by entering the 16-digit correction factor into the PCM with the help of the IDS, taking into account the relevant cylinder. Note: If the correction factors are not entered properly, the following faults can occur:
Service instructions Illustration shows top view of fuel injector
• increased black smoke formation, • irregular idling,
1
• increased combustion noise, • engine will not start. Adaptation of pilot injection by the fuel injectors: 3 2 E69913
1
Solenoid valve connector
2
16-digit correction factor
3
Leak-off pipe connection
Service Training (G1009904)
• The pilot injection of each fuel injector must be optimally preset so that the engine runs with as little combustion noise as possible. • The cylinder acceleration of each cylinder is recorded and if necessary the pilot injection adapted using the "Adaptation of pilot injection by the fuel injectors" service function. • If adaptation of pilot injection by the fuel injectors is not correctly completed, the combustion noise will be louder.
61
Test questions
Lesson 2 – Fuel System
Tick the correct answer or fill in the gaps. 1. Which of the following statements about the low-pressure system is incorrect? a. Fuel lines may be blocked due to foreign bodies or bending. b. The in-tank fuel pump supplies fuel to the high-pressure pump. c. The fuel filter must be dewatered regularly within the specified maintenance intervals. d. Faulty valves or pipes in the tank venting system can impair the flow of fuel through the low-pressure system.
2. Which of the effects listed does not apply to a blocked fuel filter? a. Engine demonstrates increased knocking noise at partial load. b. Engine has insufficient power. c. Poor engine starting performance when both cold and hot. d. Engine will not start.
3. What is the function of the transfer pump? a. The transfer pump controls fuel supply to the high-pressure chambers. b. The transfer pump delivers the required fuel to the fuel pump. c. The transfer pump generates the high pressure required for injection. d. The transfer pump cuts in as required when the high pressure in the fuel rail falls below a minimum.
4. Which of the following statements about the high-pressure system is true? a. Bosch common rail systems have only solenoid valve-controlled fuel injectors. b. The fuel rail is designed in such a way that pressure fluctuations are maximised. c. After disconnecting a high-pressure fuel line, a new one must always be installed. d. The fuel metering valve is part of the fuel rail and must not be renewed separately during servicing.
62
(G1009905)
Service Training
Lesson 3 – Powertrain Control Module (PCM) General
Inductive input signals are pulsed signals that transmit information about the engine speed and reference mark. Example of an inductive input signal:
A
B
C
E97499
• CKP. The inductive signal is processed in an internal PCM circuit. Interference pulses are suppressed and the pulsed signals are converted into digital square-wave signals. Note: Inductive sensing of the engine speed is being used less and less in modern diesel engine management systems. Hall sensors are being used more and more to sense the engine speed. Digital input signals
A
Bosch PCM
B
Siemens PCM
C
Denso PCM
The PCM is the main component of the engine management system. It receives the electrical signals from the sensors and setpoint transmitters, evaluates them and uses them to calculate the signals for the actuators. The control program (the software) is stored in a memory. The execution of the program is carried out by a microprocessor. Sensors and actuators form the interface between the vehicle and the PCM as a processing unit.
Digital input signals have only two states: • ON or OFF. Examples of digital input signals: – CMP, – CKP, – PWM (Pulse Width Modulation) signal from an APP (Accelerator Pedal Position) sensor. These signals can be processed directly by the microprocessor.
Output signals
The sensors, actuators and the power supply are connected to the PCM via three multi-pin connectors.
a b
Input signals Input signals from the sensors can have different forms. Analogue input signals Analogue input signals can have any voltage value within a given range. Examples of analogue input signals include:
a b 1
• IAT (Intake Air Temperature), • MAP (Manifold Absolute Pressure), 2
• ECT (Engine Coolant Temperature). As the microprocessor of the PCM can only process digital signals, the analogue input signals must first be converted. This is performed internally in the PCM in an analogue-to-digital converter (A/D converter).
E51118
Inductive input signals
Service Training (G1012347)
63
Lesson 3 – Powertrain Control Module (PCM) PWM signal a Fixed frequency b
Variable switch-on time
1
Signal voltage
2
Time
The microprocessor transmits output signals to the actuators via specific output stages. The output signals for the actuators can also have different forms: • Switch signals: – switch actuators on and off, for example the A/C clutch. • PWM signals: – are square-wave signals with a constant frequency, but variable turn-on time. Using these signals, electro-pneumatic transducers for example (e.g. boost pressure control solenoid valve) or actuators (e.g. electrical EGR valve) can be actuated at any location. – The duty cycle (length of the switch-on time relative to the length of the switch-off time) determines the control current to the actuator. It is of critical importance here whether the actuator is actuated pulsed to ground or pulsed to positive. – Pulsing to positive: long switch-on time = high control current, short switch-on time = low control current. – Pulsing to ground: In this case the switch-on voltage is constantly applied to the actuator. The control current results from the switching time to ground: short switching time to ground = low control current, long switching time to ground = high control current. The high-performance components for direct actuation of the actuators are integrated in the PCM in such a manner that very good heat dissipation to the housing is ensured.
Diagnosis In the case of sensor monitoring, the integrated diagnostics are used to check if there is sufficient supply to the sensors and whether their signal is in the permissible range.
64
Using the control program in the PCM it is also possible to check whether a sensor signal is within the permissible range. In the case of systems which work by means of a closed loop (e.g. the EGR system), deviations from a specific control range are also diagnosed. A signal path is deemed to be defective if a fault is present over a predefined period. The fault is then stored in the fault memory of the PCM together with freeze frame data (e.g. ECT, engine speed, etc.). Back in working order recognition is implemented for many of the faults. This entails the signal path being detected as intact over a defined period of time. Fault handling: If a signal deviates from the permissible setpoint value, the PCM switches to a default value. This process is used, for example, for the following input signals: • ECT, IAT, • MAP, BARO (Barometric Pressure), • MAF (Mass Air Flow) For some driving functions with higher priority (e.g. APP sensor), there are substitute functions which, for example, allow the vehicle to continue to be driven to the next Authorised Ford Dealer. The ECM performs self-monitoring to ensure correct operation. Malfunctions in the hardware or software of the PCM are displayed by means of a DTC. Additional monitoring (see below) is also performed:
Reference voltage monitoring In the case of reference voltage monitoring, so-called comparators compare the individual reference voltages for the relevant sensors programmed in the PCM to check if they are within limits. If a set reference voltage falls below a set limit, a DTC is stored and the engine is stopped.
EPROM (Erasable Programmable Read Only Memory) monitoring The engine adjustment data and freeze frame data are stored in the EPROM. The freeze frame data forms part of the EOBD. Incorrect entries are detected appropriately and indicated by a diagnostic trouble code.
(G1012347)
Service Training
Lesson 3 – Powertrain Control Module (PCM)
PCM and peripherals
Bosch common rail system System with "solenoid valve-controlled" fuel injectors (1.6L Duratorq-TDCi (DV) diesel engine)
1 22
23
24
3 2
5 4 25
6 21 7
26 8
9 27 10
28
11
12 13
15 29
14 19
20 30
16
17
18
31
E70768
Service Training (G1012347)
65
PCM and peripherals
Lesson 3 – Powertrain Control Module (PCM)
1
MAP sensor
18 Battery
2
Fuel pressure sensor
3
Combined IAT sensor and MAF sensor
19 DC motor for intake manifold flap with integrated position sensor (vehicles with DPF)
4
IAT sensor (only with DPF system)
5
Fuel temperature sensor
6
ECT sensor
7
CMP sensor
8
CKP sensor
9
Stoplamp switch
10 APP sensor 11 BPP (Brake Pedal Position) switch 12 DC motor for the EGR valve with integrated position sensor 13 CPP (Clutch Pedal Position) switch 14 Oil pressure switch 15 Generator (input signal) 16 Start inhibit relay
20 DC motor for charge air cooler bypass flap with integrated position sensor (Emission Standard IV) 21 PCM with integrated BARO sensor 22 CAN (Controller Area Network) 23 DLC (Data Link Connector) 24 Fuel injectors 25 Boost pressure control solenoid valve 26 Glow plug control module 27 Fuel metering valve 28 Cooling fan control and A/C compressor 29 PCM relay 30 Generator (output signal) 31 Gateway (e.g. instrument cluster or GEM (Generic Electronic Module))
17 Ignition lock
66
(G1012347)
Service Training
Lesson 3 – Powertrain Control Module (PCM)
PCM and peripherals
System with "piezo-controlled" fuel injectors (2.2L Duratorq-TDCi (DW) diesel engine)
1
2
3 4 18 5
19 6 17
20
7 21
8 22 16
15 23 9
14
10
13 26 24 12
11
25
E96169
Service Training (G1012347)
67
PCM and peripherals
Lesson 3 – Powertrain Control Module (PCM)
1
HS CAN data bus input and output signals
15 GEM**
2
MS CAN data bus input signals
16 Outside air temperature sensor
3
Gateway (GEM)
17 PCM EDC 16 CP39
4
EOP (Engine Oil Pressure) switch
18 Glow plugs
5
MAF sensor
19 Fuel injectors
6
ECT sensor
20 EGR valve with integrated position sensor
7
CKP sensor
21 Fan module
8
HO2S (Heated Oxygen Sensor)
22 Air conditioning clutch
9
IAT sensor
10 Fuel temperature sensor
23 Turbocharger variable vane electrical actuator with integrated position sensor
11 Fuel pressure sensor
24 Fuel pressure regulator
12 Oil level/temperature sensor
25 Actuator motor for intake manifold flap with integrated position sensor
13 APP sensor* 14 CPP switch * Transmits the following output signals:
26 Fuel metering valve
• PWM signal to the PCM,
** The PCM receives the following information from the GEM via hard-wired lines:
• analogue signal to the GEM.
• PCM activation ("wake up" function), • confirmation that the electric fuel pump is working properly, • signal from the stoplamp switch.
68
(G1012347)
Service Training
Lesson 3 – Powertrain Control Module (PCM)
PCM and peripherals
Siemens common rail system 1.4L Duratorq-TDCi (DV) diesel engine/2.0L Duratorq-TDCi (DW) diesel engine 24 1
25
2 26
3 4 5 6
27 7 23 8 28 9
29
10
11
22
30
38 12
31
13
37
21
32
14 15
20 19
16
17
18
36 33
35
34
E70402
Service Training (G1012347)
69
PCM and peripherals
Lesson 3 – Powertrain Control Module (PCM)
1
MAF sensor
22 Generator control (Smart Charge)
2
MAP sensor (not on all versions)
23 PCM
3
Fuel pressure sensor
24 CAN
4
IAT sensor (not on all versions)
25 DLC
5
Fuel temperature sensor
26 Fuel injectors
6
ECT sensor
7
CMP sensor
27 Turbocharger guide vane adjustment solenoid valve (not on all versions)
8
CKP sensor
9
Turbocharger position sensor
10 APP sensor (2002.25 Fiesta) 11 APP sensor (2003.75 C-MAX) 12 Stoplamp switch 13 BPP switch
28 Intake manifold flap solenoid valve (not on all versions) 29 EGR valve solenoid valve (not on all versions) 30 Fuel pump actuator (fuel metering valve and fuel pressure regulator) 31 A/C compressor and fan control magnetic clutch
14 CPP switch
32 Electric PTC (Positive Temperature Coefficient) booster heater (not on all versions)
15 VSS (Vehicle Speed Sensor) (vehicles with no ABS (Anti-lock Brake System))
33 PCM relay
16 Start inhibit relay
34 Glow plug relay
17 Ignition switch
35 Electrically controlled EGR valve (not on all versions)
18 Vehicle battery
36 Bypass solenoid valve
19 Oil pressure switch (not on all versions)
37 Shut-off solenoid valve
20 Instrument cluster
38 Electrically actuated intake manifold flap (1.4L Duratorq-TDCi (DV) diesel engine, Emission Standard IV)
21 DLC
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Lesson 3 – Powertrain Control Module (PCM)
PCM and peripherals
1.8L Duratorq-TDCi (Kent) diesel engine 23
24 25
2
1 3
4 5 26 6
7
22 27
8
9
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13 18 17
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PCM and peripherals
Lesson 3 – Powertrain Control Module (PCM)
1
MAF sensor
2
MAP sensor
19 Intake manifold flap position sensor (certain versions)
3
Fuel pressure sensor
20 Electric EGR valve
4
IAT sensor
21 Generator control (Smart Charge)
5
Fuel temperature sensor
22 PCM
6
CHT (Cylinder Head Temperature) sensor
23 CAN
7
CMP sensor
24 DLC
8
CKP sensor
25 Fuel injectors
9
KS (Knock Sensor)*
26 Intake manifold flap solenoid valve
10 APP sensor 11 Stoplamp switch 12 BPP switch 13 CPP switch 14 Start inhibit relay 15 Ignition switch 16 Vehicle battery 17 Oil pressure switch 18 Gateway**
72
27 Fuel pump actuator (fuel metering valve and fuel pressure regulator) 28 A/C compressor and fan control magnetic clutch 29 PCM relay 30 Glow plug relay 31 Turbocharger variable vane electrical actuator * The sensor is not supported by the PCM software and therefore has no function in the system. ** Can be the instrument cluster or the GEM, for example.
(G1012347)
Service Training
Lesson 3 – Powertrain Control Module (PCM)
PCM and peripherals
Denso common rail system 18
19
1
20 2
21
3 4 17 22 5
6
16 7
15
23 M
24
8 9 14
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PCM and peripherals
Lesson 3 – Powertrain Control Module (PCM)
1
CHT sensor
14 Electric EGR valve with position sensor
2
MAPT (Manifold Absolute Pressure and Temperature) sensor
15 Ignition lock
3
MAF sensor
4
APP sensor
5
Oil level/temperature sensor (certain versions only)
16 Fuel pump (with fuel metering valve and fuel temperature sensor) 17 PCM (BARO sensor integrated into the control unit) 18 CAN
6
Stoplamp switch
19 DLC
7
CKP sensor
8
CMP sensor
20 Turbocharger variable vane electrical actuator (certain versions only)
9
Fuel pressure sensor
21 Fuel injectors
10 VSS (vehicles with no ABS)
22 Glow plugs
11 Oil pressure switch
23 Cooling fan module
12 Water-in-fuel sensor (certain markets only)
24 Cooling fan
13 GEM
25 A/C cut-off relay (WAC) 26 Air conditioning clutch
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Service Training
Lesson 3 – Powertrain Control Module (PCM) Idle speed control The fuel consumption at idle is mainly determined by the idle speed and the efficiency of the engine.
Strategies
To regulate the idle speed, the injected fuel quantity is varied by the idle speed controller until the measured actual engine speed is the same as the specified setpoint engine speed.
It is advantageous to have as low an idle speed as possible, as idling is of considerable importance when driving in dense traffic (for minimising fuel consumption).
The setpoint engine speed and the control characteristic are influenced by the CHT/ECT.
However, the selected idle speed must be sufficient to ensure that, under any conditions (e.g. when the air conditioning is switched on or the vehicle electrical system is heavily loaded), it does not drop so low that the engine starts to run roughly or stalls.
• vehicle speed (engine speed compensation system),
Other variables are:
• generator control (Smart Charge) – this can increase the idle speed, • speed control system.
Fuel metering calculations Illustration shows the Siemens system
1
3
2
5
4
E98373
1
Pilot injection and main injection fuel quantity
4
ECT or CHT sensor
2
PCM
5
Fuel injector
3
CKP sensor
Diesel engines normally run without the use of a throttle plate and therefore always operate with an excess of air.
Two different strategies are used when calculating the fuel metering:
The torque or power output of the diesel engine is only changed by the amount of fuel that is made available (injected fuel quantity).
• engine starting, • engine running.
Start quantity When starting the engine, the injected fuel quantity is calculated as a function of coolant or cylinder head temperature and engine speed. The start quantity is
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Strategies
Lesson 3 – Powertrain Control Module (PCM)
output from the time the ignition is switched on until a specific minimum engine speed is reached. The driver does not have any influence on the start quantity.
1
2 5
Driving operation 3
4
Illustration shows the Siemens system
6 1 2 E47860
5
E98375
3 4
1
Calculation of accelerator pedal actuation
2
Judder damper
3
Calculation unit
4
Limiter
5
Signal to the injection pump
6
Idle speed calculation
1
Pilot injection and main injection fuel quantity
2
PCM
3
CKP
While the engine is running, the PCM uses one of the following calculations as a basis for fuel metering:
4
APP
• calculation of idle speed,
5
Fuel injector
• calculation of accelerator pedal actuation.
During normal driving operation, the injected fuel quantity is calculated from the following main variables: • APP, • engine speed. In addition, the calculation of the injected fuel quantity is influenced by other variables (correction variables), such as engine temperature and boost pressure.
Both calculations are performed continuously in parallel and independently of each other. The values calculated using the idle speed and accelerator pedal actuation are compared with each other by a calculation unit. This calculation unit then decides which calculation should be used as the output signal for the fuel injector. The calculation unit always chooses the larger value for the injected fuel quantity. Example: Engine cold – the idle speed calculation yields an idle speed of 1200 rpm and an injected fuel quantity of 7 mg. The accelerator pedal is pressed by a very small amount, and the accelerator pedal calculation provides an injection quantity of 6 mg. As the value from the accelerator pedal calculation is lower than the result for the idle speed calculation, the idle speed calculation has higher priority. If the accelerator pedal is moved further, and the accelerator pedal calculation provides a higher injected fuel quantity than the idle speed calculation as a result, then the accelerator pedal actuation calculation takes priority.
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Lesson 3 – Powertrain Control Module (PCM) Calculation of fuel metering when the speed control system is switched on Example: The vehicle is travelling in 5th gear at a speed of 100 km/h (62 mph) with an engine speed of 2500 rpm. Under these conditions, the speed control system is now switched on. Of the previously mentioned variables, it is the idle speed calculation that determines the quantity of injected fuel required to maintain the desired speed. This means that the speed in this instance is measured via the idle control system. If load conditions change (for example if driving uphill) the system attempts to maintain the speed accordingly. Once again, as the accelerator is pressed more, the accelerator pedal calculation assumes a higher priority again. The idle speed calculation assumes its original function until the next time the speed control system is switched on.
Judder damper Sudden actuation of accelerator
2 3 1 4
5 E47861
1
Engine speed
2
Abrupt actuation of accelerator pedal (driver demand)
3
Engine speed curve without active judder damping
4
Engine speed curve with active judder damping
5
Time
There is a so-called software filter between the accelerator pedal actuation calculation and the calculation unit.
Service Training (G1012347)
Strategies
When the accelerator is actuated or released suddenly, this causes huge changes in injected fuel quantity requirements and thereby also in the torque produced. Owing to this abrupt load change, unpleasant judder of the powertrain is caused in the elastic mountings (engine speed fluctuations). These are reduced by the judder damper as follows: • As engine speed increases, comparatively less fuel is injected, as engine speed decreases more fuel is injected. In addition, the software filter prevents an abrupt drop in engine speed during gear shifting.
Smooth-running control (cylinder balancing) In addition to the previously described external load moments, there are also combustion quality phenomena and internal friction moments which need to be balanced out. These change slightly, but continuously, over the entire service life of the engine. In addition, the individual cylinders do not generate the same level of torque for the entire service life of the engine. The reason for this are the mechanical tolerances and changes which occur during the service life of the engine. This could result in a rough-running engine, particularly at idle. The smooth-running control system calculates the accelerations of the crankshaft via the CKP sensor after each combustion process and compares them. Based on the engine speed variations, the injected fuel quantity for each cylinder is adjusted individually so that, as far as possible, all cylinders contribute equally to torque control.
External intervention into the injected fuel quantity In an external intervention into the injected fuel quantity, the injected fuel quantity is influenced by another control module (e.g. traction control). It informs the PCM if and how much the engine torque and consequently the injected quantity needs to be changed.
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Strategies
Lesson 3 – Powertrain Control Module (PCM)
Controlling fuel injection
Controlling the injected fuel quantity and the injection timing Injection signal to the solenoid valve of the fuel injector
1 2
1
3
2
4
6 7
5
E47864
a
Interval between start of pilot injection and start of main injection
b
Interval between pilot injection and main injection
8 E47862
1
Top dead centre
2
Pressure curve without pilot injection
c
Injected fuel quantity for pilot injection
3
Combustion pressure in the cylinder
d
Injected fuel quantity for main injection
4
Pressure curve with pilot injection
1
Pilot injection timing (degrees crankshaft angle)
5
Nozzle needle lift
2
Main injection timing (degrees crankshaft angle)
6
Nozzle needle lift with pilot injection
7
Nozzle needle lift with main injection
8
Crankshaft angle
The pilot injection brings about a preconditioning of the combustion chamber and also has the following effects: • The compression pressure is raised slightly by the initial reaction or partial combustion process, as a result of which the ignition lag for main injection is shortened and the combustion pressure rise is reduced (softer combustion). These effects diminish the combustion noise and the NOX emissions.
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With the common rail injection system, a small injected fuel quantity for pilot injection is injected into the combustion chamber prior to the main injection. The PCM calculates the overall injected fuel quantity and the injection timing. The timing of the pilot injection and main injection is designed here to be variable. This means that the timing and the duration of the pilot injection and main injection can be optimally adapted to the operating conditions. The noise and exhaust emissions are thereby kept to a minimum. Note: With certain systems, up to two pilot injection processes are initiated depending on the engine speed/load. The second pilot injection process leads to a further reduction in the noise and exhaust emissions.
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Service Training
Lesson 3 – Powertrain Control Module (PCM)
Strategies
Controlling the fuel pressure Schematic diagram of the Siemens common rail system
E70775
1
PCM
6
Fuel pressure regulator1) 2)
2
Fuel pump
7
Fuel pressure sensor
3
High-pressure chambers for high-pressure generation
8
Fuel rail
9
Solenoid valve or piezo element
4
Fuel feed
10 Nozzle needle
5
Fuel metering valve
1)
Only with the Siemens and the Bosch common rail systems with piezo-controlled fuel injectors.
Depending on the system, the fuel pressure regulator works using the following components:
2)
With the Bosch common rail system with piezo-controlled fuel injectors, the fuel pressure regulator is installed in the fuel rail.
• Bosch common rail system with "solenoid valve-controlled" fuel injectors:
Function
• Bosch common rail system with "piezo-controlled" fuel injectors:
The engine management system of the common rail injection system is capable of providing the optimum fuel pressure for each operating condition.
Service Training (G1012347)
– Fuel pressure sensor and fuel metering valve
– Fuel pressure sensor, fuel metering valve and fuel pressure regulator
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Strategies
• Siemens common rail system: – Fuel pressure sensor, fuel metering valve and fuel pressure regulator • Denso common rail system: – Fuel pressure sensor and fuel metering valve Via the high-pressure chambers of the fuel pump, fuel is pressurised and fed to the fuel rail. In the process, the delivery quantity and thus the fuel pressure is regulated by the fuel metering valve by varying the opening cross section of the fuel metering valve accordingly. The fuel pressure is regulated in such a way that the optimum pressure is available for each operating condition. On the one hand, this reduces the noise emission during fuel combustion. On the other hand, the engine management system can meter the fuel very precisely, which has a positive effect on exhaust emissions and fuel consumption. The fuel pressure sensor continuously informs the PCM about the current fuel pressure.
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Lesson 3 – Powertrain Control Module (PCM) With certain systems, the fuel pressure is additionally regulated via a fuel pressure regulator. This allows the fuel pressure to be adapted even faster to changing operating conditions. The fuel pressure supplied to the fuel rail is dependent on the engine speed and engine load.
Stopping the engine Because of the way the diesel engine works, the engine can only be stopped by interrupting the fuel supply. In the case of fully electronic engine management, this is achieved by the PCM specifying an injected fuel quantity of 0. The fuel injectors are therefore no longer actuated and the engine is stopped.
Pressure drop after the engine is stopped After the engine has been stopped, pressure is reduced through calibrated leakage in the fuel pump and the fuel injectors. For safety reasons, a certain period of time still has to elapse before the high-pressure system may be opened (see the current Service Literature).
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Service Training
Lesson 3 – Powertrain Control Module (PCM)
Strategies
EGR system 1
9 8
7
6
4
5
3
2 E51810
1
MAF sensor
6
Position sensor (integrated in the actuator motor)
2
PCM
7
Charge air cooler
3
Oxidation catalytic converter
8
EGR cooler
4
Turbocharger
9
Intake manifold flap
5
EGR valve actuator motor
By using turbochargers, the temperatures in the engine's combustion chambers rise with the torque and output.
These effects lower the proportion of NOX and also reduce the amount of exhaust gas emitted.
This results in the increased formation of NOX in the exhaust gas. In order to keep this NOX content in the exhaust gas within required limits, the EGR system is becoming increasingly important.
The quantity of exhaust gas to be recirculated is precisely determined by the PCM.
In the partial load range, exhaust gas recirculation is achieved by mixing the exhaust gases with the intake air. This reduces the oxygen concentration in the intake air. In addition, exhaust gas has a higher specific heat capacity than air. The proportion of water in the recirculated exhaust gas also reduces the combustion temperatures.
An excessive EGR rate would lead to an increase in diesel particulate, CO and HC emissions due to lack of air. Furthermore, combustion would become unstable due to a lack of O2 (Oxygen). Modern EGR systems consist of the following components: • MAF sensor, • actuator motor-controlled EGR valve with • integrated position sensor.
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Strategies
Lesson 3 – Powertrain Control Module (PCM)
Actuator motor
Intake manifold flap
The actuator motor itself is activated by the PCM depending on requirements. The opening cross section of the EGR valve depends on the PCM control current (PWM).
NOTE: Throttling of the intake air is only supported with certain versions.
MAF sensor
By partial closing of the intake manifold flap a vacuum is generated behind the intake manifold flap. The vacuum results in the exhaust gases being drawn in more efficiently by the engine via the EGR valve, enabling the EGR rate to be metered more effectively.
The quantity of exhaust gas recirculated when the EGR valve opens has a direct influence on the MAF sensor measurement. During exhaust gas recirculation, the reduced air mass measured by the MAF sensor corresponds to the value of the recirculated exhaust gases. If the quantity of recirculated exhaust gas is too high, the drawn in air mass drops to a specific limit. The PCM then reduces the proportion of recirculated exhaust gas. It is therefore a closed loop.
Position sensor In the face of increasingly stringent emission standards, EGR control via the MAF sensor alone is reaching its limits. The position sensor in the EGR valve actuator motor unit supplies a further signal to the PCM for calculating the EGR rate. This signal also allows light soiling on the EGR valve seat to be compensated. This guarantees a precise EGR rate, close to the operating limit.
A further step towards minimising NOX is the restriction of intake air via the intake manifold flap.
Effects of faults The majority of malfunctions in the EGR system are barely perceived by the driver. The only thing that can happen is increased combustion noise during idling. If, however, the EGR valve jams open or if excessive metering by the PCM takes place, the following symptoms can occur: • rough engine running, • poor engine performance, • increased emissions of black smoke.
Diagnosis The EGR control works as a system. The interaction of individual components is monitored. Malfunctions lead to increased exhaust emissions which exceed the EOBD limits. Serious faults will also lead to the EGR system being switched off. Since this is an emissions-related system, malfunctions are indicated by the MIL.
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Lesson 3 – Powertrain Control Module (PCM)
Strategies
Boost pressure control Illustration shows the boost pressure system for a turbocharger with variable turbine geometry and solenoid valve control
1 2 3
4 6 5
8
7
E47870
1
Boost pressure control solenoid valve
5
Vacuum actuator for variable turbine geometry
2
MAP sensor
6
Turbocharger
3
IAT sensor
7
PCM
4
Charge air cooler (not on all versions)
8
Vacuum pump
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Strategies
Lesson 3 – Powertrain Control Module (PCM)
Illustration shows the boost pressure system for a turbocharger with variable turbine geometry and turbocharger variable vane electrical actuator
1
2 4 3
5
E48186
1
T-MAP (Temperature and Manifold Absolute Pressure) sensor
3
Turbocharger variable vane electrical actuator
4
Turbocharger
2
Charge air cooler (not on all versions)
5
PCM
Purpose and function On a variable turbocharger, the boost pressure is regulated by adjusting the guide vanes. The optimum boost pressure can therefore be set for every operating condition.
With wastegate turbochargers (not shown here), the MAP signal is used as a safety function if the wastegate does not open after a specified boost pressure has been reached. The engine power is also reduced in this case.
Effects of faults
The boost pressure actual value is measured via the MAP sensor. The setpoint value is dependent on the engine speed and the injected fuel quantity as well as the IAT and BARO correction factors.
Faults in the boost pressure control result in reduced engine power output.
In the event of a discrepancy, the guide vanes of the variable-geometry turbocharger are re-adjusted via the boost pressure control solenoid valve or the turbocharger variable vane electrical actuator.
Faults in the boost pressure control are detected by the MAP sensor.
In the event of a malfunction of the boost pressure control system, engine power is reduced via the fuel metering system.
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Diagnosis
If the actual boost pressure deviates from the setpoint boost pressure from the map by a defined value, a limp-home program is activated in the PCM. Only a
(G1012347)
Service Training
Lesson 3 – Powertrain Control Module (PCM)
Strategies
limited injected fuel quantity is permitted in this limp-home program. This prevents engine damage through possible turbocharger overpressure.
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85
EOBD
General
Lesson 3 – Powertrain Control Module (PCM) Monitoring system for components significant for exhaust emissions (CCM) The monitoring system for components significant for emissions (CCM) continually checks to see if the sensors and actuators significant for emissions are operating within the specified tolerances when the engine is running. If a sensor or actuator is outside the tolerance range, this is recognised by the monitor and a DTC is stored in the data memory.
Monitoring of the EGR system The operation of the EGR system is monitored to identify faults that lead to increased exhaust emissions and may exceed the EOBD threshold values. E52683
The EOBD system does not use any additional sensors or actuators to individually measure pollutants in the exhaust emissions.
This monitoring system was developed so that it can, among other things, check the flow characteristics of the EGR system.
Boost pressure monitoring
The EOBD system is integrated into the software of the PCM and uses the existing sensors and actuators of the engine management system.
Boost pressure control operates via the boost pressure control solenoid valve and the MAP sensor in a closed loop.
With the aid of these sensors, actuators and the special software, systems and components significant for emissions are continually checked during the journey and exhaust emissions calculated accordingly.
The boost pressure is constantly monitored via the MAP sensor.
Components significant for emissions are checked with the so-called monitoring system.
Fuel pressure regulation operates via the fuel metering valve and the fuel pressure regulator (certain systems only). Feedback regarding the current fuel pressure is received via the fuel pressure sensor.
With the introduction of EOBD for European Ford diesel engines as of January 1, 2004 this will comprise the following monitoring systems (monitors):
Fuel pressure monitoring
MIL
• monitoring of components significant for emissions (Comprehensive Component Monitors = CCM), • monitoring of the EGR system, • boost pressure monitoring, • fuel pressure monitoring.
E48311
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Lesson 3 – Powertrain Control Module (PCM) The MIL is located in the instrument cluster and shows an engine icon (international standard). The MIL warns the driver that the EOBD system has detected an emissions-related fault in a component or system. If an emissions-related fault is detected and if this fault is confirmed during the third driving cycle, the MIL is switched on. After the MIL has been switched on, a fault log is created in the PCM. The fault logs contain information regarding the type of fault and the time since the MIL was activated. The MIL ensures that a fault is recognised in time. The defect can be repaired in good time and the emission of exhaust gas with high levels of pollutants is avoided.
Fault logging and storing
EOBD
Drive cycle A drive cycle commences when the engine starts (engine cold or hot) and ends when the engine is stopped. Depending on the complexity of the fault, the monitoring period may vary: • For simple electrical faults, a monitoring period of less than five minutes is sufficient. • For the purpose of monitoring a system (e.g. the EGR system) where different operating conditions, etc. are required to complete the test, the test can take up to about 20 minutes.
Warm-up cycle A warm-up cycle starts when the engine is started, at which point the coolant temperature must be at least 22 °C, and ends as soon as the coolant temperature exceeds 70 °C.
A fault occurring for the first time is labelled in the freeze frame data as a suspected fault (pending code) and is stored in the data memory. If the fault is not confirmed in the next check, it is erased. If it is confirmed during the third drive cycle, the suspected fault is automatically converted into a confirmed fault (continuous code). The freeze frame data does not change. It remains the same as when the fault first occurred. The MIL only illuminates when the fault has been stored as a confirmed fault. If the fault does not recur in the course of three consecutive drive cycles, the MIL extinguishes in the fourth drive cycle. However, the fault code remains stored in the data memory. Faults which do not reoccur are automatically cleared from the memory after 40 warm-up cycles. If a faulty signal is detected during a journey and the corresponding fault code is stored, all the checks in which this signal is required as a comparison variable are interrupted. This prevents follow-up faults from being stored. Diagnostic trouble codes can be read or cleared with the WDS ( Worldwide Diagnostic System) Ford diagnostic tester.
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Test questions
Lesson 3 – Powertrain Control Module (PCM)
Tick the correct answer or fill in the gaps. 1. PCM input signals a. are always analogue signals. b. are always digital signals. c. can have different forms. d. must always first be converted by an analogue-to-digital converter.
2. Which signal is used for smooth-running control? a. CKP sensor b. CMP sensor c. MAP sensor d. MAF sensor
3. How is the engine stopped? a. By a shut-off valve. b. Exclusively by closing an intake manifold flap. c. The injected fuel quantity is gradually reduced to a minimum until the engine stalls. d. The injected fuel quantity is set to 0, as a result of which the fuel injectors are no longer actuated.
4. When does the MIL indicate an emissions-related fault? a. Immediately after the fault has occurred. b. If the fault is confirmed after the second driving cycle. c. If the fault is confirmed after the third driving cycle. d. If the fault is confirmed after the second warm-up cycle.
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Lesson 4 – Sensors
Introduction
CKP sensor
Sensors record specific physical variables (e.g. temperature, pressure, engine speed, etc.) and convert them into electrical signals.
Installation position
Electrical signals can be:
A
2
• analogue voltage signals (e.g. a voltage between 0 to 5 V),
1
3
• pulsed signals (e.g. from Hall sensors),
4
• frequency-modulated signals (e.g. from a digital MAF sensor).
5
Depending on the requirement and complexity of the sensor, the electrical variables are transmitted directly to the PCM as an output signal or first processed by the sensor electronics.
B 6
Example: • An analogue voltage signal cannot be directly processed by the PCM as it is. An analogue-to-digital converter in the PCM must first convert the raw signal into the counts that the PCM can recognise. • Some sensors generate electrical signals that cannot be processed by the PCM (e.g. because the signal is too unclear or too susceptible to interference). These signals must be processed by electronics integrated in the sensor. • Pulsed square-wave signals (e.g. signals from Hall sensors) can be processed directly by the PCM.
2
3 E97572
A
CKP sensor (inductive)
B
CKP sensor (Hall)
1
CKP sensor bracket
2
CKP sensor
3
CKP sensor retaining screw
4
CKP sensor bracket retaining bolt (2 pieces)
5
CKP sensor ring gear
6
Ferro-magnetic magnet wheel
Depending on the engine, the sensor is positioned as follows: • on the transaxle side: on the cylinder block, close to the flywheel or • on the front side: on the cylinder block, close to the mass damper.
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Lesson 4 – Sensors
Purpose and function
CKP signal (Hall)
Depending on the engine and common rail system, sensors with different operating principles are used:
2
• inductive sensor or V
• Hall sensor.
1
5
The sensor scans a ring gear (inductive sensor) or a ferro-magnetic polar wheel (Hall sensor) with a clearly defined number of teeth or magnetic pole pairs (north/south).
(+)
1
Magnetic pole pairs (not visible) on magnetic disc
2
CKP sensor
3
Clearance between the pole and the CKP sensor
4
Pole gap/reference mark (not visible)
5
Square-wave signal from the CKP (Hall) sensor
3
2
A
(-) 6 7
4
E58347
Inductive CKP signal 1
3
4 1
In the case of Hall sensors, only the frequency of the signal increases with the increasing engine speed.
5
The CKP signal is used: • to determine engine speed, • for synchronisation with the CMP signal, 4
6
E58343
A
CKP signal (similar to sinusoidal voltage characteristics)
1
CKP sensor
2
Voltage (volt)
3
Pulses per crankshaft revolution (360 degrees)
4
Reference mark (gap on the ring gear)
5
Tooth centre
6
Tooth interval
7
Ring gear (flywheel or serrated disc)
The signal frequency and the height of the signal amplitude increase in proportion to the engine speed. The analogue sinusoidal signal is first converted into a square-wave signal in the PCM. Only this signal can be processed by the software.
90
• to determine the crankshaft position, • to calculate the crankshaft acceleration. The latter is used, for example, for smooth-running control (see "Lesson 3 – Powertrain control module (PCM)").
Effects of faults The CKP signal is the main input variable for calculating the injected fuel quantity and injection timing. In the event of a signal failure, the engine cannot be started or is stopped (injected quantity = 0).
Diagnosis If a specified maximum time is exceeded after the last CKP signal, there is a fault (plausibility check). This check is capable of analysing driving errors (engine stalling or cutting out).
(G1012349)
Service Training
Lesson 4 – Sensors
CMP sensor
Purpose and function
Installation position
The CMP signal is required by the PCM to activate the individual fuel injectors according to the injection sequence.
A
1
The sensor works according to the Hall principle. The digital signal is used in combination with the CKP signal to identify cylinder 1 (synchronisation with the CKP signal).
Effects of faults 3
When the engine is started, the synchronisation between the CKP signal and the CMP signal takes place in the PCM.
2
If synchronisation cannot be completed successfully, no injection enable signal is sent by the PCM, and the engine does not start (injected fuel quantity = 0).
B
4
3
If synchronisation is successfully completed, the CMP signal is of no consequence. This means that any potential CMP signal loss while the engine is running has no effect.
Diagnosis 2
E97593
A
Example on the 2.0L Duratorq-TDCi (DW) diesel engine
B
Example on the 2.4L Duratorq-TDCi (Puma) diesel engine
1
Camshaft pulley with phase sensor for CMP sensor
2
Retaining bolt
3
CMP sensor
4
Left-hand intake cam on cylinder no. 4
During engine starting, two signals (CKP and CMP) are expected by the PCM. After it has been ensured that the CKP signal is OK, the system is able to ascertain a fault in the CMP circuit.
The CMP sensor can be installed as follows: • on the cylinder head, close to the camshaft pulley (all DV and DW diesel engines), • on the intake side on the cylinder head, level with the fourth cylinder (all Puma diesel engines), • on the valve cover, level with the third cylinder (Kent diesel engine).
Service Training (G1012349)
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Lesson 4 – Sensors
MAP sensor
Effects of faults
Installation position
In the event of a fault, the guide vanes of the variable-geometry turbocharger are opened completely. Boost pressure is minimised. Furthermore, the EGR system is deactivated and the injected fuel quantity is appreciably reduced (reduced engine power output).
Illustration shows the sensor in the 2.0L Duratorq-TDCi (DW) diesel engine
Diagnosis Malfunctions lead to significantly increased emissions, as the EGR system is switched off and the boost pressure reduced to a minimum. Monitoring of the sensor consists of altogether three checking routines: • The range check determines whether the sensor values are within the limits. If the limits are not achieved or are exceeded for a certain period, the PCM interprets this as an open loop or a short circuit. 1
2
• The rise/fall check identifies intermittent faults. These indicate a loose contact at the sensor connector, among other things. • The plausibility check compares the MAP sensor signal with the BARO sensor signal. The range check is activated when the ignition is switched on, provided that no PCM power supply fault is present.
E53690
1
MAP sensor
2
IAT sensor
The sensor is located in the air intake tract between the charge air cooler outlet and the intake manifold.
Purpose and function The sensor has the following functions: • measuring the current boost pressure, • calculating the air density for adapting the injected fuel quantity and the injection timing, • calculating the turbocharger outlet temperature.
If the sensor voltage exceeds the maximum limit, the PCM interprets this as a short to positive. If the sensor voltage is below the minimum limit, the PCM interprets this as an open loop or a short to ground. The rise/fall check is also activated after the ignition is switched on, provided there is no fault in the power supply voltage to the sensor. If the PCM identifies extreme, illogical voltage jumps below/above the limits, a relevant DTC is stored. The plausibility check takes place when the ignition is switched on (engine off). The plausibility check is only performed if the limit check was completed without any faults. A prerequisite for this check, however, is that there is no plausibility fault entry stored in the fault memory of the PCM. The PCM compares the current pressure at the MAP sensor with the pressure measured at the BARO sensor for a defined period.
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If the PCM detects an excessive deviation from the target map data, it concludes that the MAP sensor is defective.
If the maximum limits are exceeded for a determined time, this is interpreted by the PCM as an open loop or a short to positive.
IAT sensor
If the minimum limits are not reached for a determined time, this is interpreted by the PCM as a short to ground.
Note: Not all versions are equipped with a separate IAT sensor. For these versions the intake air temperature is calculated by the IAT sensor integrated in the MAF sensor (see also "Combined IAT sensor and MAF sensor" in this lesson).
Installation position
The rise/fall check permits the system to detect intermittent faults (for instance a loose connector contact). In vehicles with DPF system (Emission Standard IV) a further check, the plausibility check, has been implemented. For the plausibility check, the signals of the ECT sensor, the fuel temperature sensor, the IAT sensor in the MAF sensor and the separate IAT sensor are compared with one another once the engine has cooled down. In this condition, the temperature values are approximately the same. If the check reveals that the IAT sensor value deviate from the other values by more than a specified limit, the IAT sensor is recognised as implausible and a DTC is stored.
E98379
MAPT sensor The sensor is located in the intake tract between the charge air cooler outlet and the intake manifold.
Installation position
Purpose and function The sensor contains a temperature-sensitive resistor with an NTC (Negative Temperature Coefficient). It detects the charge air temperature in order to compensate for the temperature influence on the density of the charge air. The MAF signal influences the following functions: • injected fuel quantity, • injection timing, • EGR system.
E97599
The sensor is located in the intake tract between the charge air cooler outlet and the intake manifold.
Effects of faults In the event of a fault, the PCM operates using a substitute value. This substitute value is derived from the ECT and fuel temperature.
Diagnosis
Purpose and function With this sensor, the MAP and the IAT sensors are integrated in a single component. See "MAP sensor" and "IAT sensor" in this lesson for the respective functions.
The PCM constantly checks whether the sensor values are within the limits.
Service Training (G1012349)
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Lesson 4 – Sensors
BARO sensor
ECT sensor
Installation position
Installation position
The sensor is integrated in the PCM.
Purpose and function The sensor measures the ambient air pressure. With increasing geographical altitude, the air density and therefore the air resistance decreases. This has an effect on the engine cylinder charge and the turbocharger speed. To avoid damage to the turbocharger and increased formation of black smoke, the sensor is integrated in the PCM. It is used for making appropriate adaptations to fuel metering and to exhaust gas recirculation. Note for vehicles with 1.4L Duratorq-TDCi (DV) diesel engine with Emission Standard III:
E51427
The sensor is located in the small coolant circuit of the engine.
Purpose and function
• This version has no MAP sensor for detecting the boost pressure. In this version, the BARO sensor signal is used together with the engine speed and air mass signals to calculate the boost pressure.
The sensor measures the current coolant temperature. It contains a temperature-sensitive resistor with an NTC.
Effects of faults
The ECT is used for the following calculations:
In the event of a fault, the signal from the MAP sensor is used to determine the ambient air pressure.
• idle speed,
If both sensors (BARO und MAP) are defective, the PCM uses a substitute value. In this case, the injected fuel quantity and therefore engine performance is significantly reduced.
Diagnosis The PCM continuously checks the sensor for short circuits (to ground and positive) and for open loop. The signal from the sensor is checked for plausibility by performing a comparison test with the MAP signal in a specific low load range.
The voltage value supplied by the sensor is assigned to a corresponding temperature value by the PCM.
• injection timing, • injected fuel quantity, • EGR quantity, • glow plug control, • actuation of the temperature gauge and glow plug warning indicator, • fan control.
Effects of faults When a sensor malfunctions or overheating of the engine occurs, the "engine overheating" fail-safe mode is enabled. In this mode, engine power is reduced by injecting less fuel. If the engine temperature still continues to increase, the engine power output is decreased further still, depending on the vehicle version. In fail-safe mode, the cooling fans run at maximum power.
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Diagnosis
Performing the plausibility check:
As described previously, the engine coolant temperature is used in a variety of calculations and thus has an important effect on exhaust emissions.
• After the engine has been started, the PCM assumes an ECT value.
In addition, the ECT is required to define the warm-up cycle. The monitoring system continuously checks whether the values output by the sensor are within limits. The PCM interprets deviations from limit values as an open loop or a short circuit (to ground or to battery). The sensor is checked for plausibility by a specific calibrated temperature increase having to occur in a set period of time after the engine starts. The plausibility check is only performed if the limit check was completed without any faults. Plausibility check
T
5
• If the engine speed and the injected fuel quantity exceed a calibrated value due to the temperature value assumption, a timer is started in the PCM. • During timing, the PCM checks whether a sufficient temperature increase and a calibrated minimum temperature are reached. • If this is not reached after timeout, an implausible value is assumed and a DTC is stored. • If, however, a sufficient temperature increase and a calibrated minimum temperature are reached during timing, the plausibility check is deemed to have been successful and is stopped. In the event of a fault, the engine management system reverts to a substitute value and the engine runs at reduced power output. In this case, the cooling fans are switched to run at maximum power.
4 3 2
1 t E51125
T
Engine coolant temperature
T1 Assumed engine coolant temperature T2 Minimum temperature T3 Minimum temperature not reached t
Time
1
Timer
2
Implausible temperature increase
3
Expected minimum temperature increase
4
Plausible temperature increase
5
Timer cancellation
Service Training (G1012349)
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Lesson 4 – Sensors
CHT sensor (Kent and Puma diesel engines only) Installation position
As a result, when the engine overheats (e.g. due to loss of coolant) a more precise temperature measurement is possible. The sensor is a thermistor, i.e. a negative temperature coefficient resistor (NTC resistor).
A
1
J
2 3
8 5
7 B
6
J 4
E47841
E97602
A
CHT sensor in the1.8L Duratorq-TDCi (Kent) diesel engine
B
CHT sensor in the 2.2/2.4L Duratorq-TDCi (Puma) diesel engine
1
PCM
2
Second resistor ("pull-up")
3
First resistor
4
CHT sensor (NTC)
5
Sensor output signal
6
Analogue-to-digital converter
7
Microprocessor
8
For comparison: ECT sensor
NOTE: A sensor that has already been removed may not be reused.
The output signal is an analogue voltage signal which behaves proportional to the resistance.
The sensor is located at the transaxle end of the cylinder head.
The voltage signal is digitised in the analogue-to-digital converter and transmitted in the form of counts to the microprocessor, which assigns these to the corresponding temperature values.
Purpose and function The CHT sensor is installed in place of the ECT sensor and the temperature sensor for temperature display in the instrument cluster. The CHT sensor is screwed into the cylinder head and measures the temperature of the material rather than of the engine coolant.
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At high temperatures, the resolution of the CHT sensor is not high enough to adequately cover the entire temperature range from –40 °C to +214 °C. Therefore the temperature curve is shifted by switching on a second resistor in the PCM.
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Service Training
Lesson 4 – Sensors
Example:
Shifting of the characteristic in the Visteon system
A
B 1
2
3 2
• A sensor output voltage of 2.5 V (= 500 counts) can indicate a material temperature of 35 °C as well as one of 129 °C (see diagram), depending on which characteristic the voltage value is assigned to. • When the "pull-up" resistor is activated, the microprocessor assigns the numerical value "500 counts" to the second characteristic curve. This means that the material temperature is in the higher temperature range (in this case 129 °C). Switch points with the Siemens system: • Activation point: 85 °C
---
• Deactivation point: 80 °C Use of the CHT signal: C (129)
E47842
• Injected fuel quantity
A
Counts
• Start of injection
B
Voltage (volt)
• Idle speed
C
Material (sensor) temperature
• Glow plug control
1
First characteristic
• EVAP system
2
"Pull-up" resistor switch point
3
Second characteristic
• Actuation of the temperature gauge and glow plug warning indicator
How shifting of the characteristic works is explained below using the Visteon system as an example. The first curve ranges from a material temperature of -40 °C to approx. +78 °C. A transistor in the PCM then activates a second, so-called "pull-up" resistor to extend the sensor signal function. The second curve ranges from a material temperature of approx. 62 °C to 214 °C. This means: • in the warm-up phase, the "pull-up" resistor is activated at 78 °C, • in the cool-down phase, the "pull-up" resistor is deactivated at 62 °C. The activation and deactivation point are offset to one another (hysteresis). This prevents constant activation and deactivation during constant engine operation close to the switching point.
Service Training (G1012349)
Effects of faults Open loop: • In an open loop, the system assumes a maximum temperature value of 120 °C. • In this instance, the cooling fan(s) will be running continuously and the engine will be operating at reduced power (reduced injected fuel quantity). Short circuit: • If there is a short circuit, the system assumes a temperature greater than 132 °C. • In this situation, the engine cuts out or cannot be started. When a sensor malfunction or overheating of the engine occurs, the engine overheating fail-safe mode is enabled. In this mode, engine power is reduced by injecting less fuel. If the engine temperature increases further, then the engine power is reduced further (depending on the vehicle version).
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Lesson 4 – Sensors
Note: To avoid engine damage, it is not possible to start the engine at a cylinder head temperature below –35 °C. The reason for this is the large quantities of fuel injected, which in this case might result in components being destroyed. Vehicles for cold climates have special strategies or engine preheating equipment.
The sensor registers the mass air flow into the engine. The MAF signal is used:
Diagnosis
There is an IAT sensor integrated into the MAF sensor.
The monitoring system checks:
The IAT sensor is used to correct the MAF signal at different intake air temperatures.
• the sensor for short circuit to ground/battery and open loop, • the sensor for illogical voltage jumps (illogical voltage jumps could indicate a loose connection, for example), • the signal for a plausible temperature increase.
Combined IAT sensor and MAF sensor Installation position
• as a parameter for calculating the injected fuel quantity and the injection timing, • for controlling the EGR quantity (closed loop with EGR valve).
If no separate IAT sensor is installed in the intake system downstream of the turbocharger, the IAT signal is also used for calculating the turbocharger outlet temperature. In this version, the calculated value serves as a correction factor for calculating the air density downstream of the turbocharger.
Effects of faults (MAF sensor) If the signal fails, the PCM employs a substitute value, which is calculated from the engine speed and other values. The substitute value does not, however, permit precise metering of the EGR rate. Adherence to the exhaust emission levels is no longer possible and therefore the MIL is switched on. Depending on the software strategy, the EGR system can also be switched off completely.
Effects of faults (integrated IAT sensor) E70320
The sensor is located in the air intake tract, usually directly behind the air cleaner.
Purpose and function Depending on the version, two different sensors are used:
In the event of a fault, the PCM performs the calculations using a substitute value. Furthermore, if installed, the thermo management system is controlled via a limp-home map. If installed, the electric PTC booster heater is switched off.
Diagnosis (MAF sensor)
• Analogue sensor – transmits an analogue voltage signal to the PCM, where an analogue-to-digital converter converts the signal for further processing.
The monitoring system checks:
• Digital sensor – an integrated circuit in the sensor converts the measured signal directly into a digital signal.
• the logical rise/fall rate of the signal, whereby intermittent faults are detected (e.g. loose connector contacts).
Note: In Emission Standard IV vehicles, a digital sensor is usually installed.
• for plausibility of the signal (only 1.4L Duratorq-TDCi (DV) diesel engine, Emission Standard IV).
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• the sensor for short to ground/battery (by means of a limit range check) and open loop,
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Lesson 4 – Sensors
During a test cycle, the current maximum and minimum values are compared over a specified period for the limit range check.
Malfunctions of the sensor have a significant influence on exhaust gas emissions if the recirculated exhaust gas quantity cannot be controlled precisely.
If a value exceeds/falls below the calibrated range during this test cycle, the test cycle is deemed to be faulty and a test cycle counter is activated.
An excessively low EGR quantity causes a dramatic increase in the NOX emissions, on the other hand an excessively high EGR quantity causes an increase in diesel particulate emissions.
For a certain number of test cycles, the "sound" and "faulty" test cycles are recorded, evaluated and compared with one another. The ratio of faulty test cycles to the total number of test cycles is calculated. If the result exceeds a calibrated limit, a DTC is immediately stored. The increase check (for intermittent faults) works in a similar manner.
Diagnosis (integrated IAT sensor) The monitoring system checks the integrated sensor: • for short circuit and open loop (via the limit range check), • the logical rise/fall rate of the signal, whereby intermittent faults are detected (e.g. loose connector contacts).
HO2S Installation position
E96307
The HO2S is located in the exhaust tract, downstream of the TC (Turbocharger).
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Lesson 4 – Sensors
Purpose and function
Diagnosis
The fuel injectors as well as parts of the engine management system are subject to a certain aging process over the course of time. This gives rise to variations when it comes to metering fuel as well as calculating the mass air flow.
Monitoring of the HO2S comprises the following checks:
The broadbandHO2S measures the residual oxygen content in the exhaust gas. The air/fuel ratio (lambda) can be deduced from this.
• resistance check of the Nernst oxygen cell (cannot be measured during servicing),
A more precise setpoint mass air signal can be formed for exhaust-related control circuits in accordance with the measured values. The correction of the exhaust gas recirculation has the greatest influence on this.
Turbocharger position sensor (certain versions only)
Sensing of the oxygen content in the exhaust gas therefore permits a narrower tolerance band for the recirculated exhaust gas. This has a positive effect on the exhaust emissions.
• short circuit, open circuit and open loop (includes the oxygen sensor heater circuit and the integrated sensor circuit),
• signal plausibility.
Note: The sensor is only used in the 2.0L Duratorq-TDCi (DW) diesel engine.
Installation position
The signal from the HO2S depends on the oxygen concentration in the exhaust gas as well as on the exhaust gas pressure.
1
The residual oxygen in the exhaust gas can be used to perform a comparison between the EGR setpoint map data (determined via the mass air signal) and the data actually detected. 2
The difference is stored in an adaptation map in defined learning points. This ensures fast and immediate correction of the mass air calculation, even with sudden changes in operating condition. The correction quantities are stored in the EEPROM of the PCM.
3
E53955
Effects of faults
1
Turbocharger position sensor
In the event of a fault, the emissions values increase slightly.
2
Turbocharger vacuum actuator
3
Variable-geometry turbocharger
The sensor is located at the end of the vacuum actuator of the variable-geometry turbocharger.
Purpose and function The PCM uses the sensor to obtain the exact position of the turbocharger guide vanes. This further optimises the boost pressure control. This has a positive effect on exhaust emissions and fuel consumption.
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The sensor is directly connected to the diaphragm in the vacuum actuator. When the guide vanes are adjusted (by means of a vacuum via the boost pressure control solenoid valve), the PCM determines the exact position of the guide vanes via the turbocharger sensor.
Effects of faults
Vehicle speed signal Purpose and function 2 1
No substitution strategies are available in the case of a fault. Following the detection of a fault, the boost pressure control switches to open loop. The PCM treats this fault in the same manner as a MAP sensor fault and reduces the engine power output (reduction of injected fuel quantity).
3 E53694
Diagnosis Monitoring of the sensor comprises the following checks: • Short circuits and open circuits. A check is carried out to see if the signal falls within its limits. • Logical rise/fall rate of the signal. Intermittent errors (e.g. loose contact for a plug) are determined.
1
Wheel speed sensors
2
ABS module
3
PCM
There are two methods available for detecting the vehicle speed: • using a VSS on vehicles with no ABS,
• End stop adjustment for fully opened guide vanes. If too great a deviation is detected during end stop adjustment, it indicates a blockage to the adjustment of a vane.
• using the wheel speed sensors for vehicles with ABS.
• Control deviation check. A check is made via the sensor as to whether the guide vanes adopt the correct position smoothly during adjustment.
The vehicle speed signal is used by the PCM to calculate the gear engaged and as information for the speed control integrated in the PCM.
Typical malfunction limits:
For calculation of the vehicle speed, the wheel speeds of both front wheels are detected and an average value is calculated.
• Rise/fall rate = 2 V / 10 ms • Control deviation > ± 30%
The signal from the wheel speed sensors is transmitted via the CAN data bus. The PCM calculates the vehicle speed from this.
If one or both front wheel speed sensors are faulty, the signals of both rear wheel speed sensors are used and their average is used as the vehicle speed value. If a fault occurs with the wheel speed sensors, a reliable vehicle speed signal can no longer be calculated.
Effects of faults Increased idling speed Uncomfortable juddering when changing gears Speed control system inoperative (if installed) Traction control inoperative (if installed) Reduction of injected fuel quantity
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Lesson 4 – Sensors
Diagnosis
Sensor with sliding-contact potentiometers:
The vehicle speed signal has only minor effects on exhaust gas emissions and does not exceed the EOBD limits.
• The sensor is a variable resistor which changes its resistance in response to changes in the accelerator pedal angle.
The vehicle speed signal is, however, part of the freeze frame data and is part of the EOBD. In the event of a fault, the MIL is switched on.
• For safety reasons, the sensor contains two potentiometers (APP 1 and 2).
APP sensor
• The sensor detects changes in the accelerator pedal angle inductively. The strength of the induction depends on the position of the accelerator pedal.
Installation position
Inductive senor:
• For safety reasons, the sensor is designed as a inductive double sensor (APP 1 and 2). Function of the inductive sensor within the system
E70899
In this system, the signal from APP 1 is transmitted directly as a pulse width modulated signal to the PCM. The APP 2 signal is transmitted as an analogue signal to the gateway (can be the instrument cluster or the GEM). In the gateway, the APP 2 signal is digitised, then put onto the CAN data bus and transferred to the PCM. E43365
The sensor forms one unit with the accelerator pedal.
Effects of faults Sensor with sliding-contact potentiometers:
Purpose and function The sensor forwards the driver's acceleration request to the PCM. Two different sensor types are used: • sensor with sliding-contact potentiometers (1.4L Duratorq-TDCi (DV) diesel engine only),
• If a potentiometer fails, the engine runs at reduced power output, i.e. at a maximum engine speed of 2750 rpm. • If both potentiometers fail, the engine runs at a constant engine speed of approx. 1200 rpm.
• inductive sensor.
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Inductive senor:
Fuel temperature sensor
• If one of the two sensors is faulty, the engine runs at reduced power output. However, it is still possible to achieve top speed.
Function
• If the vehicle is equipped with a driver information system, the fault message: "REDUCED ACCELERATION" is displayed.
A
2 B
• If the sensor fails completely, the engine is regulated to a speed of up to 1200 rpm after the BPP switch and the stoplamp switch have been actuated once and a plausibility check has been carried out. The vehicle can be accelerated to a maximum speed of 56 km/h. • If the vehicle is equipped with a driver information system, the error message "LIMITED TOP SPEED" is displayed. • If the vehicle is not equipped with a driver information system the "engine system fault" warning lamp illuminates when a system error occurs.
1
1 E85051
A
Fuel temperature sensor in the fuel return
B
Fuel temperature sensor at the fuel pump (Denso system only)
The monitoring system checks:
1
Fuel temperature sensor
• the sensor for short circuit to ground/battery and open loop,
2
Branch in the fuel return
Diagnosis
• the values of APP 1 and 2 for plausibility.
The sensor is located in the fuel return or directly at the fuel pump.
Purpose and function The sensor measures the fuel temperature in the low-pressure system. With the help of this signal, the fuel temperature is continuously monitored to prevent overheating of the injection system. Furthermore, the fuel density as a function of the temperature is taken into consideration when calculating the injected fuel quantity. The critical fuel temperature is approx. 90 °C. When the maximum fuel temperature is approached, the fuel pressure or the injected fuel quantity is limited accordingly.
Effects of faults Bosch and Denso systems: • In the event of a fault, the PCM assumes the maximum value. The fuel pressure and the injected fuel quantity are then reduced.
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Lesson 4 – Sensors
Siemens system:
The sensor signal is used to:
• In the event of a fault, the PCM performs the calculations using a substitute value. The substitute value is calculated from the signal from the IAT and the ECT sensors.
• determine the injected fuel quantity,
Diagnosis The monitoring system continuously checks if the signal is within the limits as well as for short circuit and open circuit. Faults in the sensor have no effect on the exhaust gas emissions.
• determine the start of injection, • actuate the fuel metering valve and, if present, the fuel pressure regulator.
Effects of faults The fuel pressure is a critical value. If the signal should fail, it is no longer possible to carry out pressure regulation and a controlled injection process. Different measures appropriate to the system are taken to protect the injection system from major damage.
Fuel pressure sensor
Bosch common rail system:
Installation position
• In the event of a short circuit or open loop, the PCM assumes a fuel pressure that is higher than the maximum permissible pressure. In response, the injected fuel quantity is set to 0 and the engine is stopped or cannot be started.
Illustration shows the fuel pressure sensor on the fuel rail of the 2.0L Duratorq-TDCi (DW) diesel engine
• The injected fuel quantity is also set to 0 if values are implausible. Siemens and Denso common rail systems:
1 E43239
1
Fuel pressure sensor
The sensor is located on the fuel rail. Note: • The sensor must on no account be removed from the fuel rail during servicing. In the event of a fault, the entire fuel rail must be renewed.
• In the event of a fault, the PCM switches from closed loop to open loop and performs calculation using an average value (Siemens approx. 350 bar/Denso approx. 600 to 1000 bar), which is made available via a limp-home characteristic map. • The average value used is within a safe range (in order to prevent excessive pressure). This means that the injected fuel quantity and therefore the engine performance are restricted. • Note: For a quick check of the sensor, disconnect the wiring harness connector while the engine is running. The engine should run more roughly. After reconnecting the wiring harness connector, the engine should return to smooth running.
Purpose and function The sensor very accurately and quickly measures the instantaneous fuel pressure in the fuel rail and delivers a voltage signal to the PCM. The fuel pressure sensor operates together with the fuel metering valve (and, if installed, the fuel pressure regulator) in a closed loop.
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Diagnosis Monitoring of the sensor comprises the following checks: • short circuit, open circuit, open loop (via the limit range check), • logical rise/fall rate of the signal (loose contact detection)
(G1012349)
Service Training
Lesson 4 – Sensors
• sensor-specific signal fluctuations, • correct pressure reduction after the engine is stopped. Monitoring of the sensor-specific signal fluctuations serves to check whether the signal emitted by the sensor is subject to "normal fluctuations". A precondition for this check is that no faults are present in the sensor supply voltage and that there is no short, open circuit or open loop. Moreover, the engine must be running in the partial load range. During monitoring, the PCM checks whether the signal fluctuations emitted by the sensor are within a calibrated minimum limit. If the fluctuations are inferior to the calibrated minimum limit, a DTC is stored.
This is in order to check whether the sensor is sticking at a certain point when emitting the signal. Monitoring for correct pressure reduction is performed after the engine is switched off using the ignition key (ignition OFF) as well as if the engine cuts out (ignition ON or OFF). The PCM checks for pressure reduction in the high-pressure system. When the engine is stopped, a timer is activated. The fuel pressure present at timeout is registered and compared with the calibrated limit in the PCM. If the measured value exceeds the calibrated limit, this leads to a DTC being stored.
Engine oil level sensor (2.4L/3.2L Duratorq-TDCi (Puma) diesel engine) Installation position
1
2 3 E64597
1
Engine oil level sensor
2
Openings
3
Oil dipstick
Service Training (G1012349)
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Lesson 4 – Sensors
At the time of going to print, the following versions are equipped with this sensor: • 2.4L Duratorq-TDCi (Puma) diesel engine with 103 kW (140 PS) and • 3.2L Duratorq-TDCi (Puma) diesel engine with 147 kW (200 PS). The sensor is installed at the cylinder block on the intake side and projects into the oil pan.
Purpose and function
The engine oil level sensor comprises a wire loop, which is immersed in the engine oil to a greater or lesser extent corresponding to the oil level. At the time of the oil level measurement, a regulator circuit in the PCM closes the circuit of the wire loop. The regulator circuit regulates a constant current flow of 195 mA through the wire loop. The constant current flow heats the wire loop in a specific way. The voltage drop (U0) across the wire loop is measured immediately after the circuit closes. Another measurement (U1) takes place approximately 1.75 seconds later. Between the first measurement (U0) and the second measurement (U1) there is a temperature drop at the wire loop. It is dependent on the extent to which the wire loop is immersed in the engine oil. The temperature drop results from the dissipation of heat from the wire loop to the engine oil. This temperature drop causes a change in resistance of the wire loop and thus also a change in the voltage drop. The voltage drop is used by the PCM as an indicator for calculating the oil level and the oil quality. The integral temperature sensor measures the current engine oil temperature and is used as a correction factor for the oil level calculation.
Prerequisites for the measurement Two conditions must be satisfied in order to ensure the measurement is correct:
1
Electrical connector
2
Wire loop
• The engine must be stopped for a period of 90 seconds. This provides an adequate return flow of engine oil into the oil pan. In this time, the power supply of the PCM is maintained (power latch phase).
3
Temperature sensor (NTC)
• The vehicle must be standing on a horizontal surface.
4
Sensor body
After completing the second measurement, the PCM calculates the oil level. The calculated value is stored.
E70772
The quality of the engine oil is calculated using this sensor and a strategy implemented in the PCM. This measure is also able to increase the oil change intervals in this version. Furthermore, the driver receives an indication via the driver information system when the engine oil level has dropped below the limit.
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Strategy for determining a horizontal surface 1
For the next "ignition ON" the lamp/text message is then no longer active. Note: Even if the engine oil has not been topped up, the indicator/text message is not active again.
3 4
The indicator/text message illuminates/appears immediately after "ignition ON" and remains active until the next "ignition OFF".
2
Calculation of the oil quality A strategy is implemented in the PCM that calculates the optimal time for an oil change.
E70773
Vref Reference voltage S
Signal to the GEM
1
Instrument cluster
2
PCM
3
GEM
4
Fuel pump and sender unit
In order to ensure a correct measurement of the oil level, the strategy of the PCM must be certain that the vehicle is standing on a horizontal surface. It assumes that the pump area of a filling station has this type of surface. For this purpose, the signal from the fuel pump and sender unit is used. If, following "ignition ON", the fuel level is significantly higher than at the last "ignition OFF", the PCM assumes that the vehicle is at a filling station and, therefore, is standing on a level surface.
This calculation is based on the continuous detection of the engine operating conditions as well as the last valid oil level measurement. If this data reveals an oil change is necessary, then this is indicated via an indicator/text message in the instrument cluster. Note: After every oil change, the parameters for the oil quality calculation must be reset (see the current Service Literature).
Engine oil level sensor (2.2L Duratorq-TDCi (DW) diesel engine) NOTE: The sensor contains a wire loop for measuring the oil level and a temperature sensor. The sensor is therefore able to transfer two input signals to the PCM. With this system, however, the PCMonly picks up the signal from the temperature sensor.
The last oil level measurement that was stored at the last "ignition OFF" is classified as a valid measurement. Only this oil level measurement is used for the calculations.
Registering an oil level that is too low If the PCM has detected refilling of the vehicle fuel tank, the last oil level measurement is compared with the map data. If the measured values indicate an oil level which is too low, a corresponding indicator/text message is displayed on the driver information system.
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Lesson 4 – Sensors
Installation position
• This can lead to the vehicle having to be brought for servicing at an earlier oil change interval. • If the PCM detects excessive oil dilution, this is shown in the instrument cluster via an indicator light and a text message.
Function
E96189
The sensor is located at the lower end of the cylinder block and projects into the oil pan.
Purpose and function The signal from the engine oil level sensor serves as an input variable for calculating the engine oil dilution by the fuel (vehicles with DPF). Reasons for use: • One or even two post-injection processes are used in some cases to raise the exhaust gas temperature during regeneration of the DPF. • In particular, the second, so-called retarded, post-injection is not ignited in the combustion chamber. Some of the fuel particles collect on the cylinder walls and get into the crankcase via the piston rings and therefore into the engine oil. • The engine oil temperature measurement is one of the input variables for the PCM for calculating the engine oil dilution by fuel. • The degree of oil dilution is mainly dependent on the engine's operating conditions. If post-injection processes are frequently required for regeneration of the DPF, the engine oil dilution is correspondingly high.
E70772
1
Electrical connector
2
Wire loop (signal is not picked off by the PCM)
3
Temperature sensor (NTC)
4
Sensor body
The sensor is designed as an NTC and is immersed in the engine oil in the oil pan. The resistance falls as the engine oil temperature increases, the resistance increases as the engine oil temperature falls.
Effects of faults If the signal fails, a corresponding text message is shown in the instrument cluster display. The PCM uses a substitute value for further calculation.
108
(G1012349)
Service Training
Lesson 4 – Sensors
Diagnosis
Stoplamp switch/BPP switch
The sensor is monitored by the PCM for short circuit and open circuit.
Installation position Illustration shows the BPP switch
Service instruction The parameters for the engine oil dilution calculation must be reset after every oil change (see the current Service Literature).
Oil pressure switch 1
2 E43363
Both switches are installed on the pedal mounting, near the brake pedal. 3
Function E52848
1
PCM
2
Instrument cluster
3
Oil pressure switch
The oil pressure in the engine's oil circuit is monitored via the oil pressure switch. If the oil pressure is incorrect, this is detected by the oil pressure switch, which then transmits a signal to the PCM. In the PCM, the signal from the oil pressure switch is placed on the CAN data bus and forwarded to the instrument cluster, causing the oil pressure warning indicator to illuminate.
The signal of the stoplamp switch influences fuel metering when the brake is applied and a gear is engaged at idle speed. Example: During braking, the PCM receives a signal from the stoplamp switch which results in the fuel quantity for idle control being reduced. This prevents the idle control system from continuing to maintain idle speed and counteracting the braking action. In addition, there is a BPP switch installed. In vehicles with a speed control system, the stoplamp switch and the BPP switch both send the "brake applied" signal to the PCM for safety reasons. In addition, the signals from both switches are used to check the APP sensor (plausibility check).
There is no fault strategy implemented.
Service Training (G1012349)
109
Lesson 4 – Sensors
CPP switch Installation position
E51434
At the pedal mounting, near the clutch pedal.
Function Using the CPP switch, the PCM identifies whether the clutch is engaged or disengaged. The quantity of injected fuel is briefly reduced during actuation of the clutch to avoid engine judder during gearshifts. The CPP switch is located on the pedal box assembly. On vehicles with speed control, the CPP switch switches off the speed control when the clutch is disengaged.
Effects in case of fault Engine judder during gearshifts.
110
(G1012349)
Service Training
Lesson 4 – Sensors
Test questions
Tick the correct answer or fill in the gaps. 1. What is avoided with the aid of the BARO sensor in the PCM? a. Excessively high engine speeds which cause the engine to overheat at increasing geographic altitudes. b. Charge air cooling at increasing geographic altitudes. c. Damage to the turbocharger and black smoke formation at increasing geographic altitudes. d. Damage to the EGR system at increasing geographic altitudes.
2. How does the PCM respond if the MAP sensor is faulty? a. Engine performance is reduced considerably. b. Boost pressure is limited to a maximum of 2.0 bar. c. The BARO sensor signal is used as a substitute value for boost pressure control. d. The MAF sensor signal is used as a substitute value.
3. Which of the following statements about the APP sensor is true? a. The APP sensor comprises a total of three sensors. b. APP sensor 1 runs directly to the PCM; APP sensor 2 runs directly to the gateway, and from there to the PCM. c. The APP sensor comprises a total of two sliding-contact sensors and one inductive sensor. d. If one of the two sensors on the APP sensor fails, the engine continues to operate unaffected.
4. What does the HO2S signal affect in the 2.2L Duratorq-TDCi (DW) diesel engine? a. Boost pressure control b. Fuel pressure control c. Exhaust gas recirculation d. Homogeneous mixture formation
Service Training (G1012350)
111
Lesson 5 – Actuators
Fuel metering valve
The fuel metering valve is bolted onto the fuel pump.
Installation position
Purpose and function
A
B
The fuel metering valve controls the fuel feed to the high-pressure chambers of the fuel pump via an opening cross section. The larger the cross section of the opening, the greater the fuel pressure generated by the fuel pump. In the case of systems without a fuel pressure regulator, the opening cross section of the fuel metering valve directly determines the fuel rail pressure.
C
E98028
A
Denso fuel pump
B
Bosch fuel pump (CP1H)
C
Siemens fuel pump (DW diesel)
Illustration shows the structure of the fuel metering valve in the Bosch common rail system
2 5 1
3
6
6
4 7
E51239
1
Coil
5
Maximum opening cross section
2
Wiring harness connector connection
6
From the transfer pump
3
Valve needle
7
To the high-pressure chambers
4
Valve closed
112
(G1012351)
Service Training
Lesson 5 – Actuators
The fuel metering valve is controlled by PWM signals from the PCM. The type of PWM is a function of: • driver's requirements, • fuel pressure requirement, • engine speed. The PWM determines the opening cross section of the fuel metering valve. NOTE: Depending on the common rail system, the fuel metering valve is either fully closed or fully open when de-energised (see table on next page). Common rail system
Fuel metering valve when de-energised Bosch (DV diesel engine) fully open • Fuel pump CP3.2 Bosch (DV diesel engine) fully closed • Fuel pump CP1H Bosch (DW diesel engine) fully open Siemens fully closed Denso fully open The type of PWM by the PCM depends on the position of the fuel metering valve when de-energised.
Effects of faults Malfunctions (e.g. a hesitant or jammed fuel metering valve) and control faults are detected by continually comparing the fuel pressure requirement (calculated by the system) and the actual fuel pressure (measured in the fuel rail). Bosch and Siemens common rail systems: • In the case of serious malfunctions, the injected fuel quantity is set to 0 (engine is stopped or cannot be started). • In the case of control faults that exceed a specific tolerance range, the injected fuel quantity is also set to 0. • In the case of control faults within a specific tolerance range, the injected fuel quantity and thus the engine performance is reduced.
Service Training (G1012351)
Denso common rail system: • In the case of control faults that exceed a specific tolerance range as well as in the case of serious malfunctions, the engine performance is significantly reduced. • The engine continues to run, but combustion noise is louder. • Note: This system features a mechanical pressure relief valve. Malfunctions in the fuel metering valve generally trigger the pressure relief valve. When the pressure relief valve is triggered, the PCM sets the DTC P0089. If P0089 is displayed when reading out the error memory, the pressure relief valve must be renewed along with the fuel metering valve.
Diagnosis NOTE: In the strategy, the fuel metering valve, the fuel pressure regulator (if installed) as well as the fuel pressure sensor operate in close interdependency and should therefore not be treated separately during fault analysis (see also "Lesson 3 – Powertrain control module (PCM)", section "Controlling the fuel pressure"). The injected fuel quantity mainly results from the engine speed and the opening time of the fuel injector, depending on the fuel pressure in the fuel rail. The fuel pressure therefore has serious effects on the exhaust gas emissions. Monitoring of the fuel pressure is a feature arising from the interaction of the fuel metering valve (adjusting the delivery quantity for the fuel rail) and the fuel pressure sensor (adjusting the desired fuel pressure). From the output shape of the pulse width modulated signals, the monitoring system identifies (by comparing it with the setpoint map data) whether the actuation is within the limits. In addition, short circuits (to ground and battery) and open circuits are monitored.
Service instructions Depending on the fuel system, the fuel metering valve can be renewed separately. With other systems, however, the entire fuel pump must be renewed. In this regard, always refer to the instructions in the current Service Literature.
113
Lesson 5 – Actuators
Denso and certain Siemens systems only: • After installing a new fuel pump or fuel metering valve and/or PCM, the new fuel metering valve must be programmed with the help of the IDS.
Fuel pressure regulator Note: A fuel pressure regulator is only installed in systems with piezo-controlled fuel injectors.
Installation position
pressure fluctuations arising during fuel supply and the injection process are compensated by the fuel pressure regulator. The fuel pressure regulator is actuated by the PCM so that the optimum fuel pressure is present in the fuel rail for all engine operating states. The fuel pressure regulator is actuated electromagnetically and is closed and opened in a controlled manner via pulse width modulated signals by the PCM. The variable actuation of the valve is a function of • driver request,
A
• fuel pressure requirement and • engine speed. Fuel pressure regulator not actuated 4
2 3
B
1 2 E53953 E98146
A
Siemens system
B
Bosch system with piezo-controlled fuel injectors
The fuel pressure regulator is located • at the fuel pump (Siemens system) or • at the fuel rail (Bosch system).
Purpose and function (Siemens system) The fuel pressure regulator regulates the fuel pressure at the high-pressure outlet port of the fuel pump and consequently the pressure in the fuel rail. In addition,
114
1
Fuel pressure at the high-pressure outlet port of the high-pressure pump
2
To the fuel return
3
Valve ball
4
Compression spring (partial section shown)
The valve ball is pressed into its seat by spring force alone. This maintains a low fuel pressure (pmin = 50 bar) at the high pressure outlet port of the fuel pump to the fuel rail. The fuel pressure regulator is therefore opened.
(G1012351)
Service Training
Lesson 5 – Actuators
The setpoint pressure in the fuel rail during starting must be at least 150 bar. Below this minimum pressure, fuel injector needle lift is not possible. The engine cannot be started or is stopped.
The force with which the armature is attracted, and consequently the pressure on the valve ball, is proportionate to the valve control current. The fuel pressure regulator closes.
Fuel pressure regulator actuated
In the case of maximum PWM actuation, the maximum required fuel pressure (depending on actuation of the fuel metering valve) is adjusted in the fuel rail.
2 5
3
Purpose and function (Bosch system with piezo-controlled fuel injectors) The structure of the fuel pressure regulator is essentially the same as with the previously described Siemens system.
4
Difference with respect to the Siemens system: • A tension spring is used instead of the compression spring.
1
• If the fuel pressure regulator is not actuated, the tension spring pulls the pin away from the valve ball.
2
7
8
• As a result, the valve ball can no longer seal the valve seat and no fuel pressure can be built up.
6
10
Effects of faults
9 E53954
The fuel pressure regulator operates together with the fuel metering valve and the fuel pressure sensor in a closed loop. If the fuel pressure regulator is defective or an electrical open circuit occurs, adequate fuel pressure cannot be built up or maintained in the fuel rail. The engine cannot be started or is stopped.
1
Fuel pressure at the high-pressure outlet port of the high-pressure pump
2
To the fuel return
3
Valve ball
4
Compression spring
5
Armature
Diagnosis
6
Coil energised
Monitoring comprises the following checks:
7
Pin
8
High fuel pressure
9
Valve control current
• The PCM checks whether the current actuation current for the fuel pressure regulator is within the setpoint range.
10 Fuel pressure regulator characteristic curve The energised coil attracts the armature. The armature transfers the magnetic force to the valve ball via the pin.
Service Training (G1012351)
With control faults, a limp-home program is activated. This permits restricted continuation of the journey to the next workshop.
• Check for short circuit and open circuit (functions via the current consumption at the PWM output stage in the PCM).
115
Lesson 5 – Actuators
Service instructions
"Two-stage" actuation of a fuel injector
In the event of repairs, the fuel pressure regulator must not be renewed as a separate component. The entire fuel pump (Siemens system) or the entire fuel rail (Bosch system) must always be renewed.
2 1 3
Fuel injectors (solenoid valve-controlled) Purpose and function
4
4
E47855
1
2
3
1
Current (in A)
2
Pull-in current
3
Holding current
4
Time
At the beginning of an injection process, the solenoid valve is actuated with a higher pick-up current so that it opens quickly. After a certain time, the pull-in current is reduced to a lower holding current. Unnecessary heat generation in the PCM is prevented in this way.
E70325
1
PCM
2
Coil
3
Solenoid armature
4
Solenoid valve
The injected fuel quantity is now determined by the opening period and the pressure in the fuel rail. The injection process finishes when the current supply to the solenoid valve is interrupted and the nozzle needle closes.
The fuel injectors are each equipped with a solenoid valve. Actuation for fuel metering is carried out by the PCM. Current is applied to the solenoid valves • in two stages (Bosch systems) • in three stages (Denso system)
116
(G1012351)
Service Training
Lesson 5 – Actuators
"Three-stage" actuation of a fuel injector (Denso system only) 2 1
1
Current (in A)
2
Pull-in current
3
Damping current
4
Holding current
5
Time
Damping current:
3
• A damping current is switched between the pick-up current and the holding current.
4 5 E99048
• The damping current reduces the voltage fluctuations when reducing the current.
Actuation currents and maximum voltages System Maximum voltage Bosch approx. 100 V Denso approx. 120 V
Pull-in current Damping current Holding current approx. 20 A approx. 12 A approx. 18 A approx. 8 A approx. 4 A Deviations from the tolerance range result in Effects of faults uncontrolled fuel metering. This means that the injected In the event of a fault, the following symptoms can fuel quantity and the injection timing cannot be occur: determined exactly (see Effects of faults). • rough engine running, In addition, the fuel injectors are checked for short • increased black smoke formation, circuit and open circuit. • loud combustion noise, • reduced engine power output. Moreover, electrical faults lead to deactivation of the smooth-running control system (cylinder balancing) and limited anti-slip regulation (no intervention in the engine management system).
Diagnosis The monitoring system is able to identify two types of malfunctions via several electrical tests:
Service instructions The solenoid valves must not be renewed separately during servicing. In the event of a fault, the entire fuel injector must be renewed. Each fuel injector is assigned an individual identification number. After installing a new fuel injector, this identification number must be communicated to the PCM with the help of the IDS (see also "Lesson 2 – Fuel system", respective "Fuel injectors" section).
• fuel metering fault of all fuel injectors, • fuel metering fault of a single fuel injector. This works by monitoring the staged power supply (current phases) of the fuel injectors (as described previously). The power consumption of the solenoid valve coil (in relation to a defined time) indicates whether the solenoid valve is working within its tolerances.
Service Training (G1012351)
117
Lesson 5 – Actuators
Fuel injectors (piezo-controlled)
Fuel injector actuation characteristic curve
Purpose and function
Characteristic curves for fuel injector actuation with pilot injection
A 1
2
B
1
2
3
4
A
E54179
B C 3 D E54178
A
Injected fuel quantity for pilot injection
B
Injected fuel quantity for main injection
1
Fuel injector needle lift (mm)
2
Actuation current (A)
3
Voltage (V)
4
Crankshaft angle (CS degrees)
A
Fuel injector closed
B
Voltage pulse from the PCM: start of charging phase, fuel injector begins to open
A brief burst of current (charge current) is required to open the fuel injector.
C
Injection
D
Voltage pulse from the PCM: start of discharging phase, injection ends
The PCM applies a charge voltage of up to approx. 140 V (Siemens system) or up to approx. 160 V (Bosch system) to the piezo element during this process.
1
PCM
2
Piezo actuator
3
Nozzle needle
The piezo-electrically-controlled fuel injectors switch up to four times faster than electromagnetically-actuated fuel injectors.
During the charging phase, the piezo element expands (elastic tension) and opens the nozzle needle. To contract the piezo element, a short burst of current in the opposite direction (discharge current) is generated. The discharge current causes the piezo actuator to return to its initial position and injection ends.
Actuation of the fuel injectors for fuel metering (start of injection and injected fuel quantity) is performed directly by the PCM, whereby the setpoint rail pressure must be at least 150 bar during startup.
118
(G1012351)
Service Training
Lesson 5 – Actuators
Note:
Service instructions
• As the injection is ended by means of the discharge current, the wiring harness connector of the piezo fuel injector must on no account be detached when the engine is running.
The piezo elements must not be renewed separately during servicing. In the event of a fault, the entire fuel injector must be renewed.
• If the wiring harness connector is detached at the moment of injection, this leads to continuous injection and engine damage.
With most systems, the fuel injectors have an identification number or a classification. In this regard, always refer to the instructions in "Lesson 2 – Fuel system", relevant "Fuel injectors" section.
Effects of faults
EGR valve
Rough engine running.
Installation position
Increased emissions of black smoke. Loud combustion noise (e.g. due to cut-off of the pilot injection).
A
Reduced engine power output. Moreover, electrical faults lead to deactivation of the smooth-running control system (cylinder balancing) and limited anti-slip regulation (no intervention in the engine management system).
Diagnosis The PCM performs various electrical checks in the individual injector electrical circuits. Electrical faults in the fuel injectors are detected via the power consumption at the piezo actuator by means of the relevant output stage in the PCM.
B
The monitoring system is able to identify two types of malfunctions using several electrical tests: • fuel metering fault of all fuel injectors, • fuel metering fault of a single fuel injector. This works by monitoring the staged power supply of the fuel injectors (as described previously). The power consumption of the piezo actuator (in relation to a defined time) indicates whether the actuator is working within its tolerances. Deviations from the tolerance range result in uncontrolled fuel metering. This means that the injected fuel quantity and the injection timing can no longer be determined precisely. In addition, the fuel injectors are checked for short circuit and open circuit.
E54181
A
Installation position on 1.4L Duratorq-TDCi (DV) diesel engine (Emission Standard IV)
B
Installation position on 2.0L Duratorq-TDCi (DW) diesel engine
Purpose and function Electrically-controlled EGR valves are predominantly installed in current diesel engines.
Certain faults (e.g. short to positive) lead to the fuel injectors no longer being actuated.
Service Training (G1012351)
119
Lesson 5 – Actuators
The EGR valve comprises the following components: • actuator motor, • position sensor, • EGR valve itself. Exhaust gas recirculation is further optimised by means of the electrically-controlled EGR valve, which has a positive effect on exhaust gas emissions. Illustration shows an excerpt of the circuit diagram of the 2.0L Duratorq-TDCi (DW) diesel engine
With increasing operating time of the engine, residues can start sticking to the valve seat of the EGR valve as a result of the exhaust gases flowing past. These residues cause the mechanical closing point of the EGR valve to move. For this reason, a cleaning/adaptation mode is activated by the PCM each time the engine is stopped. During this process, the EGR valve is moved from fully open to fully closed position, and therefore the "closing point" is redefined each time.
Effects of faults In the event of a fault, controlled exhaust gas recirculation is no longer possible and the EGR system is switched off. If the EGR sticks open, this is detected by the position sensor and the PCM then reduces the quantity of fuel injected and thus engine performance.
1
2
Diagnosis Monitoring of the EGR actuator motor is divided into three monitoring operations: 3
• monitoring of the actuator motor, • monitoring of the position sensor, • monitoring of the EGR valve.
4
In addition, the entire EGR system (interaction between the EGR valve, position sensor, actuator motor and MAF sensor) is monitored under certain operating conditions. The actuator motor is monitored for the following: 1 E54182
1
PCM
2
Actuator motor
3
Electric EGR valve
4
Position sensor
The actuator motor is a DC (Direct Current) motor. The required opening cross section of the EGR valve is approached by the PCM by means of PWM. The exact position of the EGR valve is determined via the position sensor. It is therefore a closed loop.
120
• power consumption of the actuator motor (excessively high or low current flow through the coil), • EGR valve cleaning diagnosis. The power consumption of the coil is used as a basis to check whether the signal from the PCM is within the limits. Moreover, potential overheating of the EGR valve is detected via the resistance of the coil. Cleaning diagnosis is also performed via the power consumption of the actuator motor. During cleaning, the actuator motor must open and close the EGR valve within a defined timeframe. A stuck EGR valve is detected via the current consumption of the actuator motor. Note: Cleaning/adaptation mode can be observed with the help of a IDS datalogger.
(G1012351)
Service Training
Lesson 5 – Actuators
The position sensor is monitored for the following: • limit range check: detects short and open circuits,
Pulse width modulated signals from the PCM control this vacuum via the wastegate control valve.
• logical rise/fall time of the signal: determines intermittent errors (e.g. loose contact for a plug),.
The controlled vacuum acts on the vacuum actuator in the variable-geometry turbocharger.
• plausibility check: detects a seized or sticking EGR valve.
Effects of faults
The plausibility check is started when a certain engine speed is reached. If a specific control deviation with regard to the calibrated values is detected during the check, this is interpreted as a fault by the PCM and a relevant DTC is stored.
Service instructions If a new EGR valve is installed or the PCM is renewed/reprogrammed, the EGR valve must be initialised by the PCM via the IDS.
Wastegate control valve (vacuum-controlled systems)
In the event of a fault, boost pressure control is no longer possible. Therefore, the injected fuel quantity is limited (power output reduction) and the EGR system is deactivated.
Diagnosis Boost pressure control operates in a closed loop. The adjustment of the guide vanes of the variable geometry turbocharger is carried out via the wastegate control valve. The boost pressure is controlled depending on requirements via the MAP sensor. Monitoring of the wastegate control valve comprises the following checks: • short circuit (to ground and positive) and open circuit,
Installation position
• intermittent faults (e.g. loose contact).
Illustration shows the 2.0L Duratorq-TDCi (DW) diesel engine in the 2006.5 S-MAX/Galaxy
Furthermore, wastegate control valve or vacuum system faults are detected by the MAP sensor. Wastegate control valve faults are detected by the output stage in the PCM via the power consumption of the wastegate control valve. As the EGR system is deactivated, the NOX emissions increase sharply. As a result, exhaust gas limits are exceeded.
2
1
E98158
1
Wastegate control valve
2
Intake manifold flap solenoid valve
The valve is installed at the cylinder block or at the cylinder head.
Purpose and function The wastegate control valve is provided with vacuum by the vacuum pump.
Service Training (G1012351)
121
Lesson 5 – Actuators
Intake manifold flap and intake manifold flap solenoid valve (vacuum-controlled systems)
Preventing serious engine judder when the engine is stopped: • Diesel engines have a high compression ratio. The high compression pressure of the intake air affects the crankshaft via the pistons and connecting rods and causes judder when the engine is stopped.
Installation position 1
2 3
5
• The intake manifold flap solenoid valve connects the vacuum for the intake manifold flap vacuum actuator, as a result of which the intake manifold flap is closed. This prevents engine judder when the engine is stopped. • The intake manifold flap solenoid valve is energised when the engine is stopped. The vacuum for actuation of the intake manifold flap vacuum actuator is activated and the intake manifold flap is closed briefly.
4 E54180
1
Air flow in intake manifold
2
Intake manifold flap
3
PCM
4
Intake manifold flap solenoid valve
5
Vacuum actuator
The solenoid valve is installed at the cylinder block or at the cylinder head.
Purpose and function In some versions, a vacuum-controlled intake manifold flap is used, which is actuated via an intake manifold flap solenoid valve. The intake manifold flap has the following functions: • preventing "serious engine judder" when the engine is stopped, • closing the air channel through the charge air cooler (vehicles with fuel additive diesel particulate filter),
Closing the air channel through the charge air cooler (vehicles with fuel additive diesel particulate filter): • This function is utilised when the exhaust gas temperatures are low in vehicles with diesel particulate filters. The intake manifold flap closes the air channel through the charge air cooler at the same time as the charge air cooler bypass is opened (see also "Lesson 6 – Engine emission control").
Restricting the intake air to improve the EGR rate (certain vehicles with Emission Standard IV) With certain vehicles, the normal exhaust gas recirculation is not adequate to return the required EGR rate. By slightly restricting the intake air using an intake manifold flap, a vacuum is created in the intake tract. This vacuum increases the EGR flow.
• restricting the intake air to improve the EGR rate (certain versions only), • restricting the intake air to assist the increase in exhaust gas temperature during the active DPF regeneration process (see also "Lesson 6 – Engine emission control").
122
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Service Training
Lesson 5 – Actuators
Effects of faults
Purpose and function
In the event of a signal failure or a failure of the intake manifold flap solenoid valve:
The intake manifold flap takes charge of the following functions:
• the intake manifold flap remains open when the engine is stopped. This results in increased engine judder when the engine is stopped,
• restricting the intake air for exhaust gas recirculation,
• controlled exhaust gas recirculation is only possible to a limited extent (certain versions only), • the regeneration of the diesel particulate filter cannot be performed in an ideal way under certain conditions.
Diagnosis The solenoid valve is checked for short circuit and open circuit.
Intake manifold flap actuator motor (1.6L Duratorq-TDCi (DV) diesel engine, Emission Standard IV) Installation position
• closing the intake system when the engine is stopped, • closing the air path via the charge air cooler while the regeneration of the diesel particulate filter takes place (see also "Lesson 6 - Engine emission control", section "DPF with fuel additive system"). The intake manifold flap is operated by an actuator motor. The actuator motor is a DC motor that precisely approaches the requested position of the intake manifold flap through actuation by the PCM. The actuator motor also contains a position sensor. The position sensor informs the PCM precisely of the instantaneous position of the intake manifold flap. In order to restrict the intake air flow, the intake manifold flap is closed by a set angle depending on requirements. This produces a vacuum behind the intake manifold flap. The vacuum enables the exhaust gases from the open EGR valve to be fed more efficiently to the fresh air flow.
2
Advantage: A higher EGR rate can be fed to the combustion chambers of the engine. This further reduces the NOX emissions.
1 E51373
1
Intake manifold flap
2
Charge air cooler bypass flap (vehicles with DPF only)
The actuator motor is located directly at the intake manifold flap housing. The intake manifold flap housing is flange-mounted to the intake manifold.
Service Training (G1012351)
123
Lesson 5 – Actuators
The intake manifold flap is sticking in the closed position:
1 2
• engine does not start. If the intake manifold flap is sticking, only limited control of exhaust gas recirculation is possible. Depending on the position in which it is sticking, too much exhaust gas could be recirculated under certain load conditions. In this case, the injected fuel quantity and therefore the engine's power output is reduced to prevent black smoke.
3
4
Serious faults in the position sensor will result in the EGR system being deactivated.
Diagnosis 5
Monitoring the intake manifold flap (by means of the position sensor) includes the following checks: • limit range check, • plausibility check,
2
• control deviations, • sticking intake manifold flap.
E51375
1
Voltage supply from the battery junction box
2
PCM
3
DC motor
4
Actuator motor
5
Position sensor
Most faults will result in limited exhaust gas recirculation or the EGR system being shut off.
When the engine is stopped, the intake manifold flap is closed. This prevents intake air from being drawn in and, consequently, running on (judder) of the engine. In the case of vehicles with a diesel particulate filter, the intake air temperature has to be increased under certain operating conditions for the regeneration process. To achieve this, the intake manifold flap is closed depending on requirements and a charge air cooler bypass opened (bypass of the charge air cooler) – see "Lesson 4 – Engine emission control".
Effects of faults The intake manifold flap is sticking in the open position: • EGR is limited or switched off, • when stopping the engine, increased engine judder occurs.
124
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Service Training
Lesson 5 – Actuators
Turbocharger variable vane electrical actuator Installation position
1
Turbocharger variable vane electrical actuator
2
TC
The electrical actuator is mounted directly at the TC.
Purpose and function Current diesel engines have a variable-geometry turbocharger that is actuated via an electrical actuator. 1
Its exact positioning for each operating state is achieved by the electrical adjustment of the guide vanes. This has a positive effect on exhaust emissions and helps to achieve legally prescribed exhaust emission levels.
2
E97183
A
B 1
2
3
4
7
6
5
E46463
A
Adjuster mechanism
1
Actuator motor (DC motor)
B
Control electronics
2
Actuator motor contact block
Service Training (G1012351)
125
Lesson 5 – Actuators
3
Inductive sensor unit
6
Drive pinion
4
Halfshaft
7
Actuator motor contacts
5
Worm gear
The electrical actuator consists of the following components:
Actuation via a separate line
• actuator motor,
2
• position sensor, • control unit. 1
The actuator motor (DC motor) in the actuator actuates the halfshaft via a worm gear. The halfshaft is connected to the guide vanes by the actuating lever. When the lever is actuated, the guide vanes are adjusted. E62584
There is an inductive position sensor at the end of the halfshaft. When the halfshaft is turned, a sinusoidal signal is generated inductively here. The electronics in the control unit convert the sinusoidal signal into a PWM signal. The number of square-wave signals provides exact information on the current angular position of the guide vanes. The control unit actuates the actuator motor. This actuation, depending on the type of actuation by the PCM, is more or less complex. Types of actuation by the PCM: • actuation via a separate line, • complete regulation by the PCM.
1
Turbocharger variable vane electrical actuator
2
PCM
The PCM actuates the actuator via a separate line by means of PWM signals. The actuator control unit then actuates the actuator motor accordingly. The position sensor detects the current position of the guide vanes and communicates this position to the actuator control unit. The control unit compares the PCM input parameters with the position sensor parameters and corrects the guide vane position if necessary.
NOTE: The type of actuation for the respective vehicle can be found in the wiring diagrams in the current Service Literature.
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Service Training
Lesson 5 – Actuators
Complete regulation by the PCM
Effects of faults If the actuator malfunctions, boost pressure control is no longer possible. In this case, the engine output is restricted by means of a reduction in the injected fuel quantity. An implausible boost pressure is detected by the MAP sensor, and the actuator then sets the guide vanes to the fully open position. In the event of a fault, the EGR system is switched off.
Diagnosis
E70323
The monitoring system of the actuator consists of direct and indirect monitoring.
1
Connection 1: Actuator motor (+)
2
Connection 2: Actuator motor (–)
3
Connection 3: Position sensor (–)
Direct monitoring:
4
Connection 4: Position sensor PWM output signal
• Monitoring of the PCM/actuator lines for short circuits to ground and positive.
5
Connection 5: Position sensor reference voltage
• Actuation of the actuator via a separate line:
6
PCM
7
Actuator motor
8
Position sensor (contactless)
9
Turbocharger variable vane electrical actuator
NOTE: The exact pin assignment for the plug connections can vary from vehicle to vehicle and you should always refer to the current Service Literature. In this system, a simplified electrical actuator is used. The control unit in the actuator is no longer required. Only integrated electronics convert the sinusoidal signal of the position sensor into a PWM signal. This means: • the actuator motor is actuated directly by the PCM, • the position of the guide vanes is detected directly by the PCM via the position sensor. The inductive (contactless) position sensor transmits PWM signals to the PCM. The duty cycle is determined by the position of the guide vanes. Duty cycle of the position sensor: • with minimum opening of the guide vanes (maximum boost pressure): approx. 90 % • with maximum opening of the guide vanes (minimum boost pressure): approx. 10 %
Service Training (G1012351)
– Integrated diagnosis in the control electronics of the actuator detects malfunctions in the actuator and PWM as well as voltage supply outside the standard range. • Complete regulation by the PCM: – Integrated diagnosis in the PCM detects malfunctions in the actuator and the position sensor as well as voltage supply outside the standard range. Indirect monitoring: • Indirect monitoring is performed via the MAP sensor. In the process, the engine management system checks whether the currently required boost pressure is actually being provided. • An open circuit (open loop) in the signal wire from the PCM to the actuator cannot be detected by the PCM. However, an open circuit leads to an implausible boost pressure which then results in the guide vanes of the turbocharger being set in the fully open position (minimal boost pressure). The pressure deviation is detected by the MAP sensor and a relevant DTC is set.
Service instructions The TC and the electrical actuator form a unit. The electrical actuator must not be renewed separately during servicing.
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Lesson 5 – Actuators
Electric fuel pump (2.2L Duratorq-TDCi (DW) diesel engine only) Purpose and function
1
As a result, the common rail system could take in air when cornering. The air taken in could cause major damage to the injection system. The electric fuel pump draws only fuel from the fuel pump and therefore assists with filling of the swirl pot.
2
The electric fuel pump is activated around 5 seconds after the engine starts by the PCM. The pump is deactivated again when the engine is stopped.
4
3 E96135
1
Fuel return line
2
Fuel feed line
3
Electric fuel pump
4
Swirl pot
NOTE: The purpose of the electric fuel pump in the fuel pump and sender unit is not to deliver fuel to the common rail fuel pump. The fuel filter features a bypass-controlled fuel preheater. With cold fuel, the majority of the returning fuel is returned directly to the fuel filter and therefore the fuel feed. The fuel returning to the fuel tank helps to adequately fill the swirl pot. If there is insufficient fuel returning, there may not be enough fuel in the swirl pot of the fuel pump and sender unit.
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Lesson 5 – Actuators
Test questions
Tick the correct answer or fill in the gaps. 1. Which of the following statements about the fuel metering valve is incorrect? a. It controls the fuel feed to the high-pressure chambers of the fuel pump. b. It is actuated by means of PWM signals by the PCM. c. The larger the cross section of the opening, the greater the fuel pressure delivered by the fuel pump. d. The valve is always open when de-energised in all systems.
2. Which common rail systems are equipped with a fuel pressure regulator? a. Only Siemens systems with piezo-controlled fuel injectors. b. Only Bosch systems with piezo-controlled fuel injectors. c. Only systems with piezo-controlled fuel injectors. d. Only systems with solenoid valve-controlled fuel injectors.
3. Why do piezo-controlled fuel injectors require a "discharge voltage"? a. To end fuel injection. b. To open the fuel injectors. c. To protect the piezo elements from excessive voltage peaks. d. To protect the output stage in the PCM from excessive voltage peaks.
4. The EGR valve comprises which components? a. EGR valve and position sensor b. EGR valve and actuator motor c. Actuator motor, position sensor and EGR valve d. Actuator motor, position sensor, EGR valve and EGR control unit
Service Training (G1012352)
129
Introduction
Lesson 6 – Engine Emission Control
Pollutant emissions reduction Maximum exhaust emission levels for passenger vehicles in grams per kilometre (g/km) CO (g/km) HC (g/km) NOX (g/km) HC + NOX
Emission Standard III Emission Standard IV EOBD limits
0.64
-
0.50
0.56
Particulate matter (PM) (g/ km) 0.05
0.50
-
0.25
0.30
0.025
3.20
0.40
1.20
-
0.18
In order to meet the increasingly stringent emission standards, exhaust gas aftertreatment will increase in significance even for diesel engines, despite the progress made with regard to engine modifications. By constantly improving the injection systems (direct injection in conjunction with constantly increasing injection pressures) and their electronic control, the performance, economy and comfort of the diesel engine have steadily been increased.
With regard to the imminent Emission Standard V (0.005 g/km) it is becoming clear, however, that the means by which diesel particulate emissions can be reduced through engine modifications have been virtually exhausted. A further incentive for achieving a reduction is increasing environmental awareness and the fact that the residual diesel particulate matter has a harmful effect on the human body.
Also of significance is the reduction of exhaust gas emissions, the maximum levels of which have to be continuously improved due to legal requirements.
Diesel particulates are composed mainly of a chain of carbon particles (soot) with a very large specific surface area.
The oxidation catalytic converter, in some for some years now, was the first step towards exhaust gas aftertreatment. It significantly reduced HC and CO emissions.
The noxious effect of diesel particulate matter is a result of adsorption of unburned or partially burned HC. In addition, fuel and lubricant oil aerosols (solid or liquid substances finely distributed in gases) and sulphates (depending on the sulphur content of the fuel) bind with the soot.
The measures inside the engine (high injection pressures, nozzle design, timed introduction of fuel and combustion chamber shape) have once more lowered the CO, HC and diesel particulate emissions. The NOX emissions produced by excess air in diesel combustion are more and more effectively reduced by exhaust gas recirculation systems which are constantly being improved.
Diesel particulate matter As already mentioned, a considerable reduction in diesel particulate matter has been achieved by modifications to the engine. Since the first emission standard for diesel passenger cars was introduced by the EU Commission in 1989, the limit for particulate matter has now been reduced by a factor of 44 from 1.1 g/km to only 0.025 g/km (Emission Standard IV).
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DPF (general) The use of a DPF enables the diesel particulates still emitted today to be efficiently removed from the exhaust gas. By using appropriate filter materials it is possible to retain more than 95% of the diesel particulates in the DPF. With this method almost all of the particulates can be retained, however the complete removal of diesel particulates using conventional catalytic methods is not possible. The diesel particulates are deposited in the DPF.
(G1009908)
Service Training
Lesson 6 – Engine Emission Control
Introduction
How the DPF works
E54231
1
Exhaust gas from the engine
4
DPF
2
Oxidation catalytic converter
5
Catalytically cleaned exhaust gas
3
Filtered exhaust gas
The DPF has a honeycomb structure, the walls of which are made of porous silicon carbide. In addition, the individual channels are sealed at one side and offset to each other. After combustion has occurred, some diesel particulates may still be present in the exhaust gas. As part of the filtration process, the exhaust gases loaded with diesel particulate matter flow into the DPF and are then forced to flow through the porous walls as a result of the offset position of the sealed channels. The build up of diesel particulate matter in the intermediate chambers of the porous walls increases the filtration effect still further. The DPF is always downstream of the oxidation catalytic converter.
Service Training (G1009908)
Regeneration of the DPF (general) As the collection capacity of the DPF is only limited, it has to be regenerated at regular intervals. Regeneration means burning off the deposited diesel particulates in the DPF. An exhaust gas temperature of at least 550 to 600 °C is required for burning off the deposited diesel particulates. In this temperature range, the carbon content of the diesel particulates oxidises with the O2 content present in the exhaust gas to form harmless CO2 (Carbon Dioxide). Such high exhaust gas temperatures are rarely attained, however, during actual driving. The average exhaust gas temperature for the average driving style is approx. 270 °C.
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Introduction
Lesson 6 – Engine Emission Control
In order to nevertheless attain the necessary exhaust gas temperature, different measures must be taken depending on the current exhaust gas temperature.
Intervention in the engine management system During regeneration, comprehensive control loops are activated in the engine management system depending on different temperatures and pressures. To attain the necessary temperature for regeneration, different operations are performed (e.g. throttling the intake air, post-injections, reducing the boost pressure). These operations serve to raise the exhaust gas temperature while keeping the added fuel consumption as low as possible.
Fuel additive system By adding a fuel additive to the fuel tank, the burn-off temperature of the diesel particulates can be lowered by 100 °C to approx. 450 to 500 °C. However even these exhaust gas temperatures are not always attained during average driving. The interventions by the engine management system are, however, less severe than without the use of fuel additive.
Coated DPF The filter material of this DPF is coated with a precious metal. This precious metal coating helps to convert the diesel particulates catalytically at a temperature of 300 to 450 °C (passive regeneration). However, it is often not possible to attain temperatures this high in urban traffic. In this case, the diesel particulates are deposited in the DPF. To burn them off, active regeneration must be initiated at regular intervals by means of intervention in the engine management system.
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Lesson 6 – Engine Emission Control
DPF with fuel additive system
Component overview DPF system in the 1.6L Duratorq-TDCi (DV) diesel engine
4
3
1
2 5
13
6
7
9
12
8
11 10
E48490
1
Catalytic converter exhaust gas temperature sensor
6
Instrument cluster
7
Tank flap switch
2
Catalytic converter
8
Tank flap solenoid
3
DPF differential pressure sensor
9
Fuel additive tank
4
PCM
10 Fuel additive pump unit
5
Fuel additive control unit
11 Injector
Service Training (G1009908)
133
DPF with fuel additive system
Lesson 6 – Engine Emission Control
12 Fuel tank
13 DPF
DPF system in the 2.0L Duratorq-TDCi (DW) diesel engine
1 3
2
4
14
6
5
13
7
9
8 12
11 10
E48491
1
Catalytic converter exhaust gas temperature sensor
6
Fuel additive control unit
7
Tank flap switch
2
DPF exhaust gas temperature sensor
8
Tank flap solenoid
3
DPF
9
Fuel additive tank
4
Pipes to the DPF differential pressure sensor
10 Fuel additive pump unit
5
Instrument cluster
11 Injector
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Service Training
Lesson 6 – Engine Emission Control
12 Fuel tank
DPF with fuel additive system
13 PCM 14 DPF differential pressure sensor
DPF A
B
2 1
2 1 c
d
E97467
A B
DPF/oxidation catalytic converter unit in the 1.6L Duratorq-TDCi (DV) diesel engine
1
Exhaust gas temperature sensor
2
Pipes to the DPF differential pressure sensor
DPF in the 2.0L Duratorq-TDCi (DW) diesel engine
c
Oxidation catalytic converter
d
DPF
DPF of the 1.6L Duratorq-TDCi (DV) engine: • The DPF is located downstream of the catalytic converter in the flow direction of the exhaust gases.
The soot load capacity of the DPF is limited, however, so that it has to be regenerated at regular intervals (burning of the diesel particulates).
DPF of the 2.0L Duratorq-TDCi (DW) engine:
After regeneration, ash residues that have formed from the fuel additive, engine oil and fuel remain in the DPF. These constituents cannot be further converted and can only be deposited in the DPF up to a certain degree.
• The DPF is contained in a separate housing, downstream of the oxidation catalytic converter.
This means that the DPF must be renewed at prescribed service intervals (see the current Service Literature).
• The oxidation catalytic converter and DPF are combined in one housing.
The diesel particulates contained in the exhaust gas are deposited in the DPF. The pressure drop across the DPF (measured via the DPF differential pressure sensor) is an indicator for the soot load of the filter.
Service Training (G1009908)
135
DPF with fuel additive system
Lesson 6 – Engine Emission Control
Charge air cooler bypass System in the 1.6L Duratorq-TDCi (DV) diesel engine
1 3
4
2
10 8
7
5
9
6 E51462
1
MAP sensor
6
Charge air cooler
2
Intake manifold flap housing
7
Turbocharger vacuum actuator
3
Charge air cooler bypass
8
Charge air cooler bypass flap actuator motor
4
Combined IAT and MAF sensor
9
5
Connecting piece between turbocharger and charge air cooler
Connecting piece between charge air cooler and intake manifold flap
10 Intake manifold flap actuator motor
136
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Service Training
Lesson 6 – Engine Emission Control
DPF with fuel additive system
System in the 2.0L Duratorq-TDCi (DW) diesel engine
E54232
1
Connecting piece between air cleaner housing and turbocharger
6
Charge air cooler bypass flap vacuum actuator
7
Intake manifold flap housing
2
Combined IAT and MAF sensor
8
Turbocharger
3
Charge air cooler
9
Intake manifold flap vacuum actuator
4
Connecting piece between turbocharger and charge air cooler
10 Connecting piece between charge air cooler and intake manifold flap housing
5
Charge air cooler bypass
Service Training (G1009908)
137
DPF with fuel additive system
An intake manifold flap housing has been added to the intake system in conjunction with the DPF system. The intake manifold flap housing contains the following components: • charge air cooler bypass flap, • intake manifold flap,
Lesson 6 – Engine Emission Control
intake manifold flap housing. The charge air cooler is bypassed. The charge air cooler bypass flap is only adjusted during the regeneration phase. During the regeneration phase, the air mass flowing through the charge air cooler (regulated by the intake manifold flap) is reduced.
• IAT sensor (not illustrated).
At the same time, the flow of uncooled air mass via the charge air cooler bypass (regulated by the charge air cooler bypass flap) is increased.
The intake manifold flap creates the connection between the cooled air from the charge air cooler and the intake ducts of the engine via the intake manifold flap housing.
This reduces the engine's cylinder charge while keeping the intake air temperatures constant. Variations in exhaust gas temperatures are thereby prevented during regeneration.
The charge air cooler bypass flap creates a direct connection between the compressor side of the turbocharger and the intake ducts of the engine via the
The position of both flaps is dependent on the intake air temperature. For this reason, there is an additional IAT sensor at the intake manifold flap housing, downstream of the intake manifold flap and charge air cooler bypass flap.
• MAP sensor,
Fuel additive system – general
2
1
3
4 5 6
E51469
1
Fuel tank
3
Fuel additive tank
2
Hoses for fuel additive (top up and ventilation)
4
Fuel additive pump unit
138
(G1009908)
Service Training
Lesson 6 – Engine Emission Control
5
Fuel additive line to the injector
The fuel additive system comprises the following components:
DPF with fuel additive system
6
Injector
Fuel additive tank
• a fuel additive tank with a fuel additive pump unit, • fuel additive lines,
1
• an injector.
6
In addition, a tank flap switch and a fuel additive control unit are installed in the vehicle (not illustrated).
5 2
The fuel additive is injected into the fuel tank via the fuel additive pump unit, the fuel additive line and the injector. The fuel additive mixes with the diesel fuel in the fuel tank. The quantity of the fuel additive to be injected is dependent on the diesel fuel quantity at each refuelling.
3 4 E48498
1
Fuel line to the fuel tank
2
Overflow (when filling)
Components of the fuel additive system
3
Fuel filler connection
Fuel additive
4
Fuel additive tank
5
Fuel additive pump unit
6
Vent assembly
Metallic catalysts, cerium and iron, are used as fuel additives. These accelerate burn-off of the diesel particulates and lower the temperature at which burn-off can occur. Each time after the fuel tank is filled, a metered quantity of fuel additive is injected into the fuel tank where it mixes with the fuel. When combustion takes place, the cerium and iron traces mix with the particulates from the diesel exhaust gas and provide for a considerably lower burn-off temperature. As a result, the particulate matter collected in the filter can be burned off at temperatures of just over 450 °C. The homogeneously bound cerium oxide/diesel particulate matter is then filtered out by the DPF, where it becomes embedded. Thanks to the combination of fuel additive (reduction in the burn-off temperature of the particles) and the engine management system (increase in the exhaust gas temperature), the DPF can be regenerated not only under full load conditions, but also in the partial load range at comparatively low exhaust gas temperatures typical for urban traffic.
Service Training (G1009908)
The fuel additive tank is located behind the fuel tank and is attached to the crossmember. The fuel additive tank forms a unit together with the fuel additive pump unit and can therefore only be renewed as a whole. The fuel additive tank has a capacity of 1.8 litres for an average total mileage of 60,000 km. Therefore, the fuel additive has to be topped up according to the service specifications. Note: The fuel additive tank cannot be emptied fully. Once the quantity remaining falls below 0.3 litres, fuel additive injection ceases (the driver is informed before this occurs by means of the relevant warning indicators). The residual quantity prevents the fuel additive pump from drawing in air, which could result in incorrect quantities of fuel additive being metered. The maximum top-up quantity is therefore 1.5 litres.
139
DPF with fuel additive system
Fuel additive pump unit 1 2
3
Lesson 6 – Engine Emission Control
In the event of an empty fuel additive tank, initially the engine system fault warning indicator illuminates. This means that from this point, only a residual quantity of fuel additive is available for approximately 250 litres of fuel. If the fuel additive tank is not refilled, the MIL illuminates and the fuel additive injection process is stopped. Service instructions • The fuel additive pump unit is part of the fuel additive tank and must not be renewed separately during servicing.
E48499
Injector 1
Connection to the fuel tank
2
Fuel additive pump
3
Piezo sensor
The fuel additive pump unit is designed as a displacement-type pump (piston pump). It feeds the fuel additive, metered according to the command issued by the fuel additive control unit, via a short fuel line to the injector where it is injected into the fuel tank. The piezo sensor at the bottom end of the fuel additive pump unit contains two sensor elements with the following functions: • They determine changes in the viscosity of the fuel additive as a result of changes in ambient temperature. • They detect when the fuel additive tank is empty (measurement of the precise fuel level in the fuel additive tank is also envisaged and will be implemented at a later date).
140
E48500
The injector is connected to the fuel additive tank by means of a fuel line. The fuel additive pump generates pressure in the fuel line. The injector non-return valve opens and fuel additive is fed into the fuel tank.
(G1009908)
Service Training
Lesson 6 – Engine Emission Control
DPF with fuel additive system
Component overview – system control Components of the Bosch system
8
1
9
7
10
2 11
3
6
4 12
5
E70769
1
DPF exhaust gas temperature sensor
7
PCM
2
DPF differential pressure sensor
8
CAN
3
IAT sensor
9
DLC
4
Tank flap switch and solenoid (in the tank flap)
10 Charge air cooler bypass flap actuator motor
5
Piezo sensor on the fuel additive pump unit
11 Intake manifold flap actuator motor
6
Fuel additive control unit
12 Fuel additive pump
Service Training (G1009908)
141
DPF with fuel additive system
Lesson 6 – Engine Emission Control
Components of the Siemens system
E70774
1
Catalytic converter exhaust gas temperature sensor
7
Fuel additive control unit
8
PCM
2
DPF exhaust gas temperature sensor
9
CAN
3
DPF differential pressure sensor
10 DLC
4
IAT sensor
11 Charge air cooler bypass flap solenoid valve
5
Tank flap switch and solenoid (in the tank flap)
12 Intake manifold flap solenoid valve
6
Piezo sensor on the fuel additive pump unit
13 Fuel additive pump
142
(G1009908)
Service Training
Lesson 6 – Engine Emission Control
PCM During the regeneration phase, the PCM partially assumes control of the system.
DPF with fuel additive system
Fuel additive control unit Installation position
During the regeneration phase, completely different parameters are required for engine management. For this reason, the PCM is equipped with an additional data set for the regeneration phase. The fuel additive system is monitored by a separate fuel additive control unit which communicates with the PCM via the CAN data bus. The PCM and the fuel additive control unit can be diagnosed by means of the WDS via the DLC connection.
1
Service instructions When installing a new PCM or before loading new software as well as when installing a new DPF, always read the instructions in the current Service Literature.
E48493
1
Fuel additive control unit
The fuel additive control unit is located under the right-hand rear seat.
Purpose and function A separate fuel additive control unit is responsible for fuel additive injection. It is connected to the PCM via the CAN data bus. The fuel additive control unit detects when the vehicle has been refuelled on the basis of various input variables and subsequently controls metering of the fuel tank additives to be injected into the fuel tank. The fuel additive control unit also features a counter function. Using this counter, the fuel additive control unit calculates the level in the fuel additive tank by recording the frequency with which the fuel additive pump unit is actuated and the duration of these actuations.
Service Training (G1009908)
143
DPF with fuel additive system
Lesson 6 – Engine Emission Control
As soon as the level in the fuel additive tank drops below a specific, calculated quantity remaining, the engine system fault warning indicator in the instrument cluster is actuated, indicating in this case that the quantity of fuel additive remaining is sufficient for approximately 250 litres of fuel.
Diagnosis
This means that in the case of a fuel tank with a capacity of 50 litres, sufficient fuel additive remains available for approximately five complete refuelling operations or, for example, for ten refuelling operations at 25 litres each.
The PCM registers the CAN fault data from the fuel additive control unit and subsequently logs a corresponding DTC.
Information concerning the actual quantity of fuel added is sent by the fuel level sensor. With a properly functioning system, a minimum tank quantity of 5 litres is registered. If the engine system fault warning indicator illuminates, this is a signal to the driver that they should drive to the nearest Authorised Ford Workshop as soon as possible. If the driver does not do this, the MIL is set when the fuel additive tank has been emptied completely.
The fuel additive system is a stand-alone system controlled by the fuel additive control unit. The fuel additive control unit detects faults in the fuel additive system and sends these via the CAN bus.
Faults in the fuel additive system can lead to illumination of both the engine system fault warning indicator and the MIL. In the event of CAN communication failure, the MIL is also actuated. Possible fault codes: P2584, P2585, U0118
Fuel additive pump unit Function
To indicate an empty fuel additive tank, the fuel additive control unit sends the appropriate information via the CAN bus to the PCM, which logs a DTC and, in turn, actuates the corresponding indicator in the instrument cluster, also via the CAN bus. Note: If one of the previously mentioned lamps illuminates to indicate that the fuel additive tank is empty, the corresponding DTC must be cleared in the fault memory by means of the WDS once the fuel additive tank has been refilled. In addition, the counter must be reset with the help of the IDS. Note: The fuel additive tank cannot be emptied fully. Once the quantity remaining falls below 0.3 litres, fuel additive injection ceases (the driver is informed before this occurs by means of the relevant warning indicators). The residual quantity prevents the fuel additive pump from drawing in air, which could result in incorrect quantities of fuel additive being metered.
Effects of faults If a damaged fuel additive control unit means that fuel additive can no longer be added to the fuel, then the DPF can no longer be systematically regenerated. The result is a blocked DPF.
144
1 2
3
E48499
1
Connection to the fuel tank
2
Fuel additive pump
3
Piezo sensor
The fuel additive pump unit consists of the fuel additive pump and a two-piece piezo sensor. The internal piezo sensor can only detect when the fuel additive tank is empty. In conjunction with the counter of the fuel additive control unit, this device therefore makes doubly sure that an empty fuel additive tank can be detected. Note: There are plans to enable the external piezo sensor to detect the precise level and these will be implemented at a later date.
(G1009908)
Service Training
Lesson 6 – Engine Emission Control
The external piezo sensor establishes the changing viscosity of the fuel additive affected by the ambient temperature and sends this reference value to the fuel additive control unit. On the basis of this input signal, the fuel additive control unit is able to precisely determine the injection time for the fuel additive. The fuel additive pump is actuated by the fuel additive control unit using pulse width modulation and supplies the injector on the fuel tank with a precise quantity of fuel additive due to its defined stroke.
Tank flap switch Installation position
1
DPF with fuel additive system
If a clear signal is received from the tank flap switch as a result of opening and closing the tank flap and if an increase in the fuel quantity (differential quantity) of at least 5 litres is detected in the fuel tank once the ignition has been turned on, the fuel additive control unit assumes that refuelling has taken place. The fuel additive control unit calculates the fuel additive quantity to be injected according to the differential quantity calculated, and activates the fuel additive pump. Activation/metering is performed as soon as the vehicle exceeds a speed of 40 km/h or, if this speed is not reached, 4 minutes after the engine is first started. Note: After the fuel additive tank has been filled (as part of a scheduled service), the counter in the fuel additive control unit must be reset. It can be reset by opening and closing the tank flap in a certain way and use should be made of this feature (see the current Service Literature). Resetting the counter via the tank flap switch is not possible if either the engine system fault warning indicator or the MIL has illuminated as a result of the fuel additive tank becoming empty. In this case, the counter must be reset with the help of the IDS. When the tank flap is closed, the tank flap switch is open.
Effects of faults
2 E51571
If the signal from the tank flap switch fails, small refuelling quantities (below 10 litres) cannot be detected.
1
Solenoid (in the tank flap)
The software in the fuel additive control unit has been designed to only allow fuel additive to be injected in the case of a missing signal from the tank flap switch if the refuelling quantity is at least 10 litres.
2
Tank flap switch (reed contact)
The tank flap switch is incorporated into the fuel tank filler shroud. The actuating solenoid is located in a bracket at the tank flap.
Purpose and function The tank flap switch is designed as a reed contact and informs the fuel additive control unit when the fuel tank is filled. However, the fuel additive control unit only registers that refuelling has taken place if detected by the fuel level sensor in addition to the tank flap switch signal and if the vehicle speed is less than 3 km/h.
Service Training (G1009908)
The reason for this is that, in the worst case scenario, the vehicle may, for example, have been rolled onto a slope with the "ignition OFF". Then, when the ignition is next switched on, the fuel additive control unit could register an increased quantity of fuel via the fuel level sensor and might misinterpret this as a refuelling operation. To prevent fuel additive from being injected unnecessarily, if the tank flap switch is faulty the fuel level difference is increased from at least 5 litres to a minimum of 10 litres. If the signal fails, the engine system fault warning indicator is actuated.
145
DPF with fuel additive system
Lesson 6 – Engine Emission Control
Exhaust gas temperature sensor(s)
Effects of faults
Installation position
Bosch system: • In the event of a fault, the PCM reverts to a substitute value. The substitute value is calculated on the basis of: – coolant temperature, – engine speed, – engine load. Siemens system:
E48497
The Bosch system • has just one exhaust gas temperature sensor. This is located directly in the oxidation catalytic converter/DPF unit upstream of the DPF. The Siemens system • has a catalytic converter exhaust gas temperature sensor and a diesel particulate filter exhaust gas temperature sensor.
• If a fault occurs in one of the two sensors, the value of the other exhaust gas temperature sensor is used by the PCM. • If both the sensors are defective, a substitute value is calculated.
Diagnosis The following checks are carried out: • short and open circuit (by means of a limit range check),
Purpose and function
• logical rise/fall rate of the signal, by which means intermittent errors (e.g. loose connector contact) are determined,
The exhaust gas temperature of at least 450 °C to 550 °C required for burning off the diesel particulates is detected by the sensor(s) and transmitted to the PCM.
• plausibility (after engine start-up, a certain temperature increase is expected by the PCM within a certain period).
The exhaust gas temperature input variable is used for calculation purposes by the PCM, which also takes other parameters into account.
A faulty sensor has no direct influence on exhaust emissions. As regeneration is, however, significantly impaired and clogging of the DPF is possible, the MIL is set in the event of a fault.
Depending on the exhaust gas temperature calculated, the PCM decides whether or not the regeneration process can be initiated. Through the arrangement of the two sensors, the exhaust gas temperature required for regeneration can be adjusted and monitored very precisely. The regeneration process cannot be terminated unless a minimum temperature of 450 °C is reached and maintained.
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DPF with fuel additive system
DPF differential pressure sensor
Diagnosis
Installation position
The monitoring system performs the following checks via the sensor: • plausibility check, • DPF efficiency, • DPF overloaded, • DPF blocked, • monitoring of the maximum regeneration attempts in the lower load range. The plausibility check is divided into two tests:
E59691
The differential pressure sensor is located in the engine compartment, near the bulkhead.
Purpose and function The sensor measures the current exhaust gas pressure upstream and downstream of the DPF and determines the differential pressure based on the readings. For this purpose there is a pipe connection upstream and downstream of the DPF. The readings are converted by the sensor into a voltage signal and transmitted to the PCM. The soot particles and ash collected in the DPF result in a change in pressure in the exhaust gas stream upstream and downstream of the DPF. The change in pressure is used by the PCM as an input variable for determining the soot load. If the measured value exceeds the programmed maximum value, regeneration of the DPF is initiated, taking into account the necessary boundary conditions. In addition, the sensor is also used for diagnosing the condition of the DPF.
Effects of faults In the event of a fault, the PCM reduces the engine power output by reducing the injected fuel quantity.
Service Training (G1009908)
• With the engine running: The differential pressure is measured via the DPF. This is determined according to the difference between the anticipated pressure of the exhaust gas stream as calculated by the PCM and the actual pressure of the exhaust gas stream before and after it passes through the DPF. This test is performed under certain operating conditions (depending on coolant temperature, engine speed and engine load – regeneration not activated). Assuming that these conditions are met, the sensor signal must be within the specified limits. • With the engine switched off: Here, the differential pressure is measured before the engine is started or immediately after it has been switched off. If the differential pressure calculated via the DPF is greater than the value specified by the PCM, this is recognised as an implausibility. The DPF efficiency test determines whether the filter material in the DPF is in sound condition. The DPF element itself poses a certain resistance to the exhaust gas stream that is calculated by the PCM. To achieve the calculated exhaust gas stream, the test is performed under certain operating conditions. If the value measured here is below the minimum value calculated, the DPF is recognised as inefficient. A DPF is recognised as overloaded if the differential pressure across the DPF exceeds the overload limit calculated by the PCM. A DPF is recognised as blocked if the differential pressure exceeds the blocking limit calculated by the PCM.
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DPF with fuel additive system
Lesson 6 – Engine Emission Control
Monitoring of the maximum regeneration attempts in the lower load range: the DPF regeneration system is designed to enable regeneration to be performed even under unfavourable conditions (low coolant temperature, engine speed and engine load).
Charge air cooler bypass flap actuator motor (Bosch system only) Purpose and function
In the worst case scenario, the system may start regeneration attempts but be unable to complete them. These attempts are counted by the PCM. If the maximum number of regeneration attempts is reached, this results in a fault entry the next time the ignition is switched on.
Intake manifold flap actuator motors (Bosch system only) E51674
Purpose and function
During the regeneration phase, the charge air cooler bypass flap opens, enabling uncooled charge air to be directed to the combustion chambers.
2
The uncooled air prevents cooling of the combustion chamber at low engine speeds/engine loads and this promotes the regeneration of the DPF. The charge air cooler bypass flap actuator motor incorporates a DC motor and a position sensor which detects the current position of the intake manifold flap.
1 E51373
1
Intake manifold flap actuator motor
2
Charge air cooler bypass flap actuator motor
In the de-energised state (actuator motor not actuated), the charge air cooler bypass flap is fully closed.
During the regeneration phase, the intake manifold flap closes off the air flow via the charge air cooler depending on requirements. At the same time, uncooled charge air is fed via the charge air cooler bypass flap. The intake manifold flap actuator motor incorporates a DC motor and a position sensor which detects the current position of the intake manifold flap. In the de-energised state (actuator motor not actuated), the intake manifold flap is fully open.
Effects of faults In the event of a fault, limited regeneration is still possible depending upon how high the intake air temperature is and the operating condition of the engine. Note: For further information on the intake manifold flap actuator motor, refer to "Lesson 5 - Actuators".
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DPF with fuel additive system
The DC motor is supplied with battery voltage by means of the ignition relay in the battery junction box.
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The actuation of the DC motor and therefore the adjustment of the charge air cooler bypass flap is performed by the PCM connecting to ground (pulse width modulated).
3
The position sensor is supplied with a reference voltage. The voltage drop at the position sensor (variable resistance via sliding contact) signals the precise angular position of the charge air cooler bypass flap to the PCM.
Effects of faults In the event of a fault, limited regeneration is still possible depending upon how high the intake air temperature is and the operating condition of the engine.
2
Diagnosis
4
1
Monitoring of the charge air cooler bypass flap (by means of the position sensor) includes the following checks: • reference voltage of the position sensor,
E51722
• limit range check,
1
PCM
• plausibility check,
2
Actuator motor
• control deviations,
3
Position sensor
• sticking charge air cooler bypass flap.
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DC motor
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DPF with fuel additive system
Lesson 6 – Engine Emission Control
Intake manifold flap and charge air cooler bypass flap solenoid valves (Siemens system) Purpose and function
E54236
1
Intake manifold flap vacuum actuator
4
Charge air cooler bypass flap solenoid valve
2
Charge air cooler bypass flap vacuum actuator
5
PCM
3
Intake manifold flap solenoid valve
The intake manifold flap has another function in addition to restricting the intake air for exhaust gas recirculation and closing the intake system when the engine is stopped. During the regeneration phase, the intake manifold flap closes off the air flow via the charge air cooler depending on requirements. At the same time, uncooled charge air is fed via the charge air cooler bypass flap. Adjustment of the intake manifold flap is performed by the intake manifold flap solenoid valve via vacuum.
Effects of faults If a fault occurs at one (or both) of the two solenoid valves, limited regeneration is still possible depending upon how high the intake air temperature is and the operating condition of the engine.
Diagnosis Both solenoid valves are monitored for short and open circuit.
During the regeneration phase, the charge air cooler bypass flap opens, enabling uncooled charge air to be directed to the combustion chambers. The uncooled air prevents cooling of the combustion chamber at low engine speeds/engine loads and this promotes the regeneration of the DPF. Adjustment of the charge air cooler bypass flap is performed by the charge air cooler bypass flap solenoid valve via vacuum. In accordance with the requirements, the solenoid valves are actuated at a specified duty cycle by the PCM.
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Lesson 6 – Engine Emission Control Coated diesel particulate filter (DPF)
Overview of the DPF Illustration shows the DPF in the exhaust tract of the 2.2L Duratorq-TDCi (DW) diesel engine
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1
3
4
6 E97474
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7
1
Oxidation catalytic converter
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Rear pipe to the DPF differential pressure sensor
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Flexible pipe
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Front pipe to the DPF differential pressure sensor
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DPF exhaust gas temperature sensor
7
4
DPF
Catalytic converter exhaust gas temperature sensor
The coated DPF is shaped like a honeycomb and is made from silicon carbide, similar to the DPF in the system with fuel additive (see relevant section in this Student Information). A passive regeneration of the DPF is possible at temperatures above 300 °C with the aid of the coating (platinum ceroxide). In this temperature range, the trapped diesel particulates are converted catalytically. The exhaust gas temperature required for passive regeneration is often not attained. In this case, the trapped diesel particulates must be burned off from time to time with the aid of an active regeneration process.
Passive regeneration The exhaust gases flow through the walls of the silicon element. In doing so, the diesel particulates remain adhered to the ceramic wall that has been coated with a platinum ceroxide layer.
Service Training (G1009908)
Oxidation of carbon monoxide (CO) and hydrocarbon (HC): • As with the oxidation catalytic converter, CO and HC are oxidised. With high levels of CO and HC exhaust emissions, the energy release is considerable. The resultant jump in temperature acts directly at the point at which high temperatures are required for oxidising the diesel particulates. Oxidation of nitrogen monoxide (NO) into nitrogen dioxide (NO2): • NO is oxidised into NO2 at the catalytic coating. • NO2 is a more active oxidation agent than O2 and therefore oxidises the diesel particulates even at low exhaust gas temperatures (from 300 to 450 °C approx.). The effect is known as the CRT (Continuously Regenerating Trap) effect or as passive regeneration.
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Coated diesel particulate filter (DPF) Lesson 6 – Engine Emission Control
Oxidation of carbon monoxide (CO) into carbon dioxide (CO2):
However, if it is necessary to install a new DPF, a parameter reset must be performed via the IDS.
• Another operative mechanism is the oxidation of the CO, which is produced at low regeneration temperatures during the oxidation of diesel particulates, into CO2. The combustion of diesel particulates is improved by the localised generation of heat.
With some versions, the parameters of the DPF differential pressure sensor must also be reset. In this regard, always refer to the instructions in the current Service Literature.
At temperatures from 300 °C to 450 °C (attained largely outside of cities), a passive regeneration of the DPF therefore takes place continuously. It is not necessary for the engine management to intervene.
High exhaust gas temperatures of approx. 600 °C must be generated for active regeneration of the coated DPF.
Active regeneration For situations where the vehicle is frequently driven for short distances, active regeneration must be initiated at certain intervals. The PCM registers the engine's operating data and initiates active regeneration after evaluating the data from the DPF differential pressure sensor. An attempt is then made by the engine management system to attain the necessary temperature of approximately 600 °C for combusting the trapped diesel particulates. The following measures are taken to achieve this: • a post-injection close to the main injection, • increasing the injected fuel quantity, • retarded main injection, • restricting the intake air via an intake manifold flap, • a second post-injection at a distance from the main injection (if necessary). Note: The measures listed above are not always all active. The map decides the measures that have to be taken to increase the temperature as a function of the operating conditions. During active regeneration, the EGR system is deactivated. The active regeneration process can take up to 20 minutes.
Notes on the oil change interval
With frequent journeys in the lower partial load range, the maximum number of available measures must usually be taken to attain the exhaust gas temperature necessary for an active regeneration. The intervals between the individual regeneration processes are then also shorter, so that the maximum number of available measures have to be taken more often. When using the maximum number of available measures, retarded post-injection is frequently used. Retarded post-injection results in a greatly increased dilution of the engine oil. In extreme cases, this means that the engine lubrication is no longer adequately guaranteed. In order to detect excessively diluted engine oil, an oil quality calculation strategy has been implemented in the PCM software. This strategy calculates the oil quality, taking into consideration the engine operating conditions and the measures for increasing the exhaust gas temperature during the regeneration processes. If the strategy determines more than 7 % fuel in the engine oil, a corresponding text message is activated in the instrument cluster. This text message signals to the driver as well as to the Ford Service personnel that an oil change must be carried out ahead of schedule. After each oil change, the parameters for the oil quality calculation must be reset (see also the instructions in the current Service Literature).
Service instructions The coated DPF is installed in the vehicle for life. It therefore has no maintenance intervals (at the time of going to print).
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Lesson 6 – Engine Emission Control Coated diesel particulate filter (DPF)
DPF regeneration indicator (2006.5 Transit only)
If in addition to the DPF regeneration indicator and the MIL the transmission control indicator is also switched on, a new DPF must be installed. Note: If the vehicle is mainly operated with sufficient exhaust gas temperatures, it is very possible that the DPF regeneration indicator will never come on. With sufficient exhaust gas temperatures, the vehicle is always able to independently initiate and complete the necessary regeneration processes.
Intake manifold flap Installation position Illustration shows the system with vacuum control
E98563
It is not always the case that vehicles are operated in the temperature ranges required for regeneration of the DPF. The indicator indicates to the driver when there is a risk of the DPF becoming overloaded. E98519
Illumination of the indicator signals to the driver that the vehicle needs to be operated at a higher engine speed to initiate and complete an active regeneration process. To this end, the vehicle should be driven at a higher engine speed for at least 30 minutes. Long periods of idling should be avoided. The indicator goes out again following successful regeneration. The vehicle can now be used as normal. If the required active regeneration process cannot be successfully completed, in addition to the DPF regeneration indicator, the MIL is also switched on. If this happens, the vehicle must be brought to the nearest Authorised Ford Dealer. The technician can initiate active regeneration using the IDS.
Service Training (G1009908)
The intake manifold flap is located in a housing that is mounted directly on the intake manifold.
Purpose and function A high temperature (approx. 600 °C) is needed to burn off the diesel particulates trapped in the DPF. This temperature, however, is not attained in all of the engine's operating conditions. Under certain operating conditions, the intake manifold flap is partially closed in the lower partial load range. The resulting lack of fresh air intake results in the combustion chambers no longer being cooled as sharply. This helps to increase the exhaust gas temperature.
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Coated diesel particulate filter (DPF) Lesson 6 – Engine Emission Control
Components of the engine emission control system
1
2
7
8 9
3
6
4
5 10
11 E98520
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Catalytic converter exhaust gas temperature sensor
7
CAN
8
DLC
2
DPF exhaust gas temperature sensor
9
3
DPF differential pressure sensor
Intake manifold flap solenoid valve (only with vacuum-controlled systems)
4
MAP sensor
10 Fuel injector
5
Intake manifold flap position sensor (only with vacuum-controlled systems)
11 Intake manifold flap unit (with systems with electrical actuator unit)
6
PCM
Service instructions Before installing a new PCM or before loading new software as well as after installing a new DPF differential pressure sensor, always read the instructions in the current Service Literature.
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Lesson 6 – Engine Emission Control Coated diesel particulate filter (DPF)
Exhaust gas temperature sensor(s)
Diagnosis
Installation position
The monitoring system checks: • the sensor for short circuit to ground/battery and open loop, • logical rise/fall rate of the signal, whereby intermittent faults are detected (e.g. loose connector contacts), • for plausibility.
DPF differential pressure sensor Installation position E48497
One or two sensors are installed, depending on the system. System with one sensor: • The sensor is located immediately upstream of the DPF. System with two sensors: • One sensor is located upstream of the oxidation catalytic converter and • one sensor is located immediately upstream of the DPF.
Purpose and function The exhaust gas temperature of at least 550 °C to 600 °C required for burning off the diesel particulates is detected by the sensor(s) and transmitted to the PCM. Depending on the exhaust gas temperature calculated, the PCM decides whether or not the regeneration process can be initiated.
Effects of faults In the event of a fault, the PCM calculates a substitute value. Specific regeneration of the DPF, however, is no longer possible.
E59691
The differential pressure sensor is located in the engine compartment, near the bulkhead.
Purpose and function The sensor measures the current exhaust gas pressure upstream and downstream of the DPF and determines the differential pressure based on the readings. For this purpose there is a pipe connection upstream and downstream of the DPF. The readings are converted by the sensor into a voltage signal and transmitted to the PCM. The soot particles and ash collected in the DPF result in a change in pressure in the exhaust gas stream upstream and downstream of the DPF. The altered pressure value owing to the ash/soot load is used by the PCM as an input variable for determining soot and ash load.
Service Training (G1009908)
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Coated diesel particulate filter (DPF) Lesson 6 – Engine Emission Control
Furthermore, the sensor detects a defective DPF.
Effects of faults If the sensor is defective, the PCM calculates the timing of the next regeneration.
Intake manifold flap position sensor (vacuum-controlled systems) Installation position
Overloaded or blocked DPF: • The PCM continuously calculates the load status of the DPF from the engine's operating conditions and from the input variable of the sensor. • With an increasing soot load, the engine torque is also continuously reduced. • If the DPF is blocked, the MIL is set.
Diagnosis The monitoring system checks: • the sensor for short circuit to ground/battery and open loop, • the measured sensor values for plausibility (comparison with the map data). Via the sensor, the monitoring system detects: • an overloaded/blocked DPF. (The pressure drop across the filter is too great and the differential pressure exceeds a calibrated maximum value.)
E97945
The sensor is installed at the intake manifold flap housing, near the intake manifold flap.
Purpose and function In vehicles with coated DPF, the exact position of the intake manifold flap has an effect on the active regeneration process (see the section "Intake manifold flap" in this lesson). The sensor works inductively (contactless) and is therefore insensitive to slight contamination.
• a defective/missing DPF. (The pressure drop across the filter is too low and the differential pressure falls below a calibrated minimum value.)
The sensor is supplied with a reference voltage (5 V ± 5 %). The analogue output signal to the PCM is between 5 and 95% of the reference voltage.
Service instructions
Effects of faults
With some systems, it is necessary to carry out a parameter reset using the IDS after installing a new sensor. In this regard, always refer to the instructions in the current Service Literature.
Specific regeneration is only possible to a limited extent. In extreme cases, this leads to overloading of the DPF and thus to reduced engine power output.
Diagnosis The monitoring system checks: • the sensor for short to ground/battery (by means of a limit range check) and open loop, • the logical rise/fall rate of the signal, whereby intermittent faults are detected.
Service instructions Following installation of a new sensor, it must be initialised using the PCM (refer to the instructions in the current Service Literature).
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Lesson 6 – Engine Emission Control Coated diesel particulate filter (DPF)
Intake manifold flap unit
Diagnosis
Installation position
Intake manifold flap unit monitoring is divided into the following steps:
Intake manifold flap unit with integrated actuator motor and position sensor
• Monitoring of the DC motor via the PCM output stage • Monitoring of the position sensor: – Limit monitoring: the PCM constantly checks if the incoming signal is within the limits. – Monitoring for short circuit and open circuit. – Reference voltage monitoring. • Monitoring of the intake manifold flap:
E98522
The unit is mounted directly at the intake manifold.
Purpose and function The intake manifold flap is partially closed as required during the active regeneration process. This helps to increase the exhaust gas temperature.
– The position sensor detects a jammed or sticking intake manifold flap.
Service instructions With some systems, it is necessary after installing a new intake manifold flap unit to carry out an initialisation using the IDS. In this regard, always refer to the instructions in the current Service Literature.
The intake manifold flap unit consists of the following components: • intake manifold flap, • actuator motor, • position sensor. The intake manifold flap is operated by a DC motor. Actuation is performed via PWM by the PCM. The current position of the intake manifold flap is detected by a position sensor (potentiometer). The output signal is an analogue voltage signal.
Effects of faults Specific regeneration is only possible to a limited extent. In extreme cases, this leads to overloading of the DPF and thus to reduced engine power output. If the intake manifold flap becomes jammed closed, the engine cannot be started.
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Fuel vaporiser system
Lesson 6 – Engine Emission Control
General
1
2
8
2
7
3 9
4 5 6
E98530
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Fuel vaporiser system fuel pump
6
Fuel outlet bore
2
Fuel line
7
Electrical connection for glow plug
3
Non-return valve
8
Main oxidation catalytic converter
4
Fuel vaporiser
9
DPF with integrated oxidation catalytic converter
5
Centring
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Lesson 6 – Engine Emission Control
NOTE: At the time of going to print, the fuel vaporiser system is only planned for the 2.4L Duratorq-TDCi in the 2006.5 Transit.
Fuel vaporiser system
Fuel vaporiser system fuel pump Purpose and function
For space reasons, the coated DPF of the 2.4L Duratorq-TDCi (Puma) diesel engine is located far behind the main oxidation catalytic converter. The exhaust gas temperature (approx. 600 °C) generated by engine-based measures for active regeneration of the DPF would cool too rapidly before the DPF is reached. Active regeneration of the DPF would therefore not be possible. To attain the necessary exhaust gas temperature for active regeneration, a fuel vaporiser system is installed here. With the help of the fuel vaporiser system, vaporised fuel is injected to the exhaust tract. The vaporised fuel reacts in the second oxidation catalytic converter, which is located immediately upstream of the DPF. This second oxidation catalytic converter and the DPF are contained in a single housing. Through the reaction of the vaporised fuel in the second oxidation catalytic converter, the exhaust gas temperature of around 600 °C required for burning off the trapped diesel particulates is attained. The fuel vaporiser system is actuated by the PCM under the following conditions: • The trapped diesel particulates must be burned off with the aid of an active regeneration process. • The exhaust gas temperature upstream of the DPF must be at least 205 °C. The fuel vaporiser system is activated during the entire active regeneration process (approx. 10 - 15 minutes).
Service instructions After working on the fuel vaporiser system (e.g. after renewing the fuel vaporiser system fuel pump or one of the fuel lines), the system must be bled. After cleaning the fuel system (e.g. due to incorrect refuelling of the vehicle with petrol), the fuel vaporiser system must also be cleaned and then bled.
E98544
The fuel vaporiser system fuel pump is a reciprocating piston pump. The pump stroke is generated electromagnetically. All cavities are filled with fuel in currentless state. When the solenoid coil is energised, the solenoid armature pushes the pump plunger against a spring. The pump plunger opens a non-return valve in the pump and expels the fuel. The pump plunger simultaneously closes the bores to the pump chamber. At the same time, the armature chamber is filled with new fuel. If the power is switched off, the spring pushes the solenoid armature and the pump plunger back. This creates a vacuum and the fuel enters via the bore. The pump delivers fuel to the fuel vaporiser for the duration of the regeneration process. The fuel pump is actuated by the PCM during active regeneration with a frequency of 6 Hz.
Service instructions After installing a new fuel vaporiser system fuel pump, the fuel vaporiser system must be bled. In this regard, always refer to the instructions in the current Service Literature.
Effects of faults If the pump is defective, active regeneration can no longer be carried out. The result is a blocked DPF.
In this regard, always refer to the instructions in the current Service Literature.
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Fuel vaporiser system
Lesson 6 – Engine Emission Control
Fuel vaporiser Purpose and function 2
1
3
4
5 E97163
1
Fuel vaporiser
2
Glow plug
3
Fuel vaporiser chamber
4
Fuel outlet bore
5
Non-return valve
At the start of the regeneration process, the glow plug in the fuel vaporiser is actuated by the PCM. A few seconds later, the fuel vaporiser system fuel pump delivers fuel to the fuel vaporiser chamber. The delivered fuel flows past the heated glow plug, vaporising in the process. The vaporised fuel then flows into the exhaust tract via the outlet bore. The non-return valve ensures the necessary pressure and prevents the fuel line draining. The fuel is admitted into the fuel vaporiser chamber at a pressure of less than 2 bar.
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Lesson 6 – Engine Emission Control
Test questions
Tick the correct answer or fill in the gaps. 1. What is the fuel additive used for? a. To enhance the performance of the engine. b. To lower the NOX emissions during the regeneration process. c. To support the combustion of HC emissions inside the engine. d. To lower the combustion temperature for the deposited diesel particulates.
2. What is the advantage of the coated DPF? a. No interventions by the engine management system are required. b. Active regeneration can take place at 300 °C. c. The fuel additive tank is designed with a large enough volume so that no fuel additive needs to be topped up for the service life of the vehicle. d. No fuel additive is required.
3. What must be performed on vehicles with coated DPF after each oil change? a. A reset of the parameters for the soot load of the DPF. b. A reset of the parameters for the oil quality calculation. c. A reset of the differential pressure sensor parameters. d. A visual inspection of the DPF for signs of overheating.
4. The fuel vaporiser system a. pumps fuel from the EVAP (Evaporative Emission) canister directly into the exhaust tract. b. injects vaporised fuel into the exhaust tract. c. injects vaporised fuel directly into the engine cylinder during the exhaust stroke. d. injects vaporised fuel directly into the intake tract.
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Answers to the test questions
Lesson 1 – General Information 1. b 2. c 3. d 4. c Lesson 2 – Fuel System 1. b 2. a 3. b 4. c Lesson 3 – Powertrain Control Module (PCM) 1. c 2. a 3. d 4. c Lesson 4 – Sensors 1. c 2. a 3. b 4. c Lesson 5 – Actuators 1. d 2. c 3. a 4. c Lesson 6 – Engine Emission Control 1. d 2. d 3. b 4. b
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Service Training
List of Abbreviations
ABS
Anti-lock Brake System
IDS
Integrated Diagnostic System
APP
Accelerator Pedal Position
KS
Knock Sensor
BARO
Barometric Pressure
MAF
Mass Air Flow
BDC
Bottom Dead Center
MAP
Manifold Absolute Pressure
BPP
Brake Pedal Position
MAPT
Manifold Absolute Pressure And Temperature
CAN
Controller Area Network MIL
Malfunction Indicator Lamp
CHT
Cylinder Head Temperature NOX
Oxides Of Nitrogen
CKP
Crankshaft Position NTC
Negative Temperature Coefficient
CMP
Camshaft Position O2
Oxygen
CO
Carbon Monoxide PATS
Passive Anti-theft System
CO2
Carbon Dioxide PCM
Powertrain Control Module
CPP
Clutch Pedal Position PTC
Positive Temperature Coefficient
DC
Direct Current PWM
Pulse Width Modulation
DLC
Data Link Connector TC
Turbocharger
DPF
Diesel Particulate Filter TDC
Top Dead Center
DTC
Diagnostic Trouble Code T-MAP
ECT
Engine Coolant Temperature
Temperature And Manifold Absolute Pressure
EGR
Exhaust Gas Recirculation
VSS
Vehicle Speed Sensor
EOBD
European On-board Diagnostic
WDS
Worldwide Diagnostic System
European On-Board Diagnostics EOP
Engine Oil Pressure
EPROM
Erasable Programmable Read Only Memory
EVAP
Evaporative Emission
GEM
Generic Electronic Module
HC
Hydrocarbon
HO2S
Heated Oxygen Sensor
IAT
Intake Air Temperature
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