Technical service training diesel injection and engine management systems

More stringent exhaust and noise emission standards and calls for lower fuel consumption continue to place newdemands on the fuel injection and engine management systems of diesel engine

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

More stringent exhaust and noise emission standards and calls for lower fuel consumption continue to place newdemands 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 combustionchamber 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 optimuminjection 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 exactlycalculated 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 filtersystem 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 prerequisitefor 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 aredesigned to monitor the student's progress The solutions to these test questions can be found at the end of theStudent Information

Please remember that our training literature has been prepared for FORD TRAINING PURPOSES only Repairsand adjustments MUST always be carried out according to the instructions and specifications in the workshopliterature Please make full use of the training offered by Ford Technical Training Courses to gain extensiveknowledge of both theory and practice

Preface

1 Preface

Lesson 1 – General Information

6 Overview of the systems

10 Introduction

11 Injection characteristics

13 Torque

13 Emission Standard IV with or without DPF

13 Cleanliness when working on the common rail system

14 Test questions

Lesson 2 – Fuel System

15 Overview

20 Low-pressure system

20 General

21 Bosch common rail system

21 Fuel filter

25 Overview of the high-pressure system

27 Fuel pump

33 Fuel rail (common rail)

33 High-pressure fuel lines

33 Fuel injectors (general)

34 Solenoid valve-controlled fuel injectors

37 Piezo-controlled fuel injectors

42 Siemens common rail system

42 Fuel filter

43 Overview of the high-pressure system

44 Fuel pump

47 Fuel rail and high-pressure fuel lines

48 Fuel injectors

53 Denso common rail system

53 Fuel filter

54 Overview of the high-pressure system

55 Fuel pump

58 Fuel rail and high-pressure fuel lines

60 Fuel injectors

62 Test questions

Table of Contents

Lesson 3 – Powertrain Control Module (PCM)

63 General

63 Input signals

63 Output signals

64 Diagnosis

65 PCM and peripherals

65 Bosch common rail system

69 Siemens common rail system

73 Denso common rail system

75 Strategies

75 Idle speed control

75 Fuel metering calculations

77 Smooth-running control (cylinder balancing)

77 External intervention into the injected fuel quantity

78 Controlling fuel injection

79 Controlling the fuel pressure

81 EGR system

83 Boost pressure control

86 EOBD

86 General

87 Fault logging and storing

88 Test questions

Lesson 4 – Sensors

89 Introduction

89 CKP sensor

91 CMP sensor

92 MAP sensor

93 IAT sensor

93 MAPT sensor

94 BARO sensor

94 ECT sensor

96 CHT sensor (Kent and Puma diesel engines only)

98 Combined IAT sensor and MAF sensor

99 HO2S

100 Turbocharger position sensor (certain versions only)

101 Vehicle speed signal

102 APP sensor

Table of Contents

103 Fuel temperature sensor

104 Fuel pressure sensor

105 Engine oil level sensor (2.4L/3.2L Duratorq-TDCi (Puma) diesel engine)

107 Engine oil level sensor (2.2L Duratorq-TDCi (DW) diesel engine)

109 Oil pressure switch

109 Stoplamp switch/BPP switch

110 CPP switch

111 Test questions

Lesson 5 – Actuators

112 Fuel metering valve

114 Fuel pressure regulator

116 Fuel injectors (solenoid valve-controlled)

118 Fuel injectors (piezo-controlled)

119 EGR valve

121 Wastegate control valve (vacuum-controlled systems)

122 Intake manifold flap and intake manifold flap solenoid valve (vacuum-controlled systems)

123 Intake manifold flap actuator motor (1.6L Duratorq-TDCi (DV) diesel engine, Emission Standard IV)

125 Turbocharger variable vane electrical actuator

128 Electric fuel pump (2.2L Duratorq-TDCi (DW) diesel engine only)

129 Test questions

Lesson 6 – Engine Emission Control

130 Introduction

130 Pollutant emissions reduction

130 DPF (general)

131 Regeneration of the DPF (general)

133 DPF with fuel additive system

133 Component overview

135 DPF

136 Charge air cooler bypass

138 Fuel additive system – general

139 Components of the fuel additive system

141 Component overview – system control

143 PCM

143 Fuel additive control unit

144 Fuel additive pump unit

145 Tank flap switch

146 Exhaust gas temperature sensor(s)

Table of Contents

147 DPF differential pressure sensor

148 Intake manifold flap actuator motors (Bosch system only)

148 Charge air cooler bypass flap actuator motor (Bosch system only)

150 Intake manifold flap and charge air cooler bypass flap solenoid valves (Siemens system)

151 Coated diesel particulate filter (DPF)

151 Overview of the DPF

151 Passive regeneration

152 Active regeneration

152 Notes on the oil change interval

153 DPF regeneration indicator (2006.5 Transit only)

153 Intake manifold flap

154 Components of the engine emission control system

155 Exhaust gas temperature sensor(s)

155 DPF differential pressure sensor

156 Intake manifold flap position sensor (vacuum-controlled systems)

157 Intake manifold flap unit

158 Fuel vaporiser system

158 General

159 Fuel vaporiser system fuel pump

160 Fuel vaporiser

161 Test questions

162 Answers to the test questions

163 List of Abbreviations

Table of Contents

Overview of the systems

Bosch common rail system with "solenoid valve-controlled" fuel injectors

E51104

Lesson 1 – General Information

Bosch common rail system with "piezo-controlled" fuel injectors

E96077

Lesson 1 – General Information

Siemens common rail system

E53583

Lesson 1 – General Information

Denso common rail system

E69955

Assignment of the common rail systems to the engines

Denso Siemens

Bosch Engine

X1.4L Duratorq-TDCi (DV)

diesel

X1.6L Duratorq-TDCi (DV)

Denso Siemens

Bosch Engine

X2.0L Duratorq-TDCi (DW)

diesel

X2.2L Duratorq-TDCi (DW)

(Puma) diesel

* 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,

• shaping of injection timing characteristics,

• multiple injections,

• values for injected fuel quantity, start of injectionand boost pressure adapted to every operatingcondition,

• load-independent idle speed control,

• closed-loop EGR (Exhaust Gas Recirculation),

• low injection timing and injected fuel quantitytolerances and high degree of precision over theentire service life,

• possibility of interaction with other systems such asstability 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 injectionpressure is generated independently of engine speed andinjected fuel quantity

The common rail injection system consists of ahigh-pressure pump and a fuel rail (fuelaccumulator/rail) This fuel rail offers constant pressurefor distributing fuel to the electrically-controlled fuelinjectors

With this type of diesel injection or engine management,the driver has no direct influence on the injected fuelquantity For example, there is no mechanical connection

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),

• operating condition,

• engine temperature,

• effects on exhaust emissions,

• prevention of engine and transmission damage,

• 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)

Injection characteristics

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

Consequently, the following requirements must be met

by the common rail system:

• The injection timing must be exact Even small

variations have a significant effect on fuel

consumption, exhaust emissions and combustion

noise

• The fuel injection pressure is independently adapted

to all operating conditions

• 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

Simple main injection

Needle lift of the fuel injector nozzle and pressure curve

in a cylinder without pilot injection

TDC (Top Dead Center)3

Needle lift with simple main injection4

Crankshaft angle5

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

The fuel is then injected mechanically into the

combustion chamber by the injector nozzles in twoseamlessly integrated stages (two-spring nozzle carrierprinciple)

In the pressure curve, the combustion pressure increasesonly slightly in the phase before TDC corresponding tocompression, but increases very sharply at the start ofcombustion

The sharp pressure rise intensifies the combustion noise

Lesson 1 – General Information

Pilot injection

Needle lift of the fuel injector nozzle and pressure curve

in a cylinder with pilot injection

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

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 asignificant improvement in the running smoothness ofthe 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)

Needle lift of the injector nozzle with pilot and post-injection

Pilot injection2

Crankshaft angle3

Main injection4

Advanced post-injection5

Retarded post-injection6

For vehicles with a DPF (Diesel Particulate Filter)

system, two post-injections are employed during the

regeneration process, in addition to the pilot and maininjections, 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 toraise the exhaust gas temperature during the regenerationprocess of the DPF In addition, some of the dieselparticulates produced during regeneration areafter-burned

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

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

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

Measures for the reduction of exhaust emissions insidethe engine include, for example:

• further optimised exhaust gas recirculation by means

of an electrically-controlled EGR system with intakeair restriction,

• optimisation of the combustion chamber design andthe 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 ofEmission 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 isessential that scrupulous cleanliness is observed whencarrying out any work on the system

In this regard, refer to the instructions in the currentService Literature

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 combustionnoise

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

Lesson 1 – General Information Test questions

Fuel rail (common rail)2

Fuel injector3

Fuel temperature sensor4

Fuel return collector pipe5

Lesson 2 – Fuel System

Fuel pump1

Fuel rail2

Fuel injector3

Lesson 2 – Fuel System

Siemens common rail system

E53588

7 8

6

4

F A

Fuel rail (common rail)2

Fuel injector3

Fuel return collector pipe4

Lesson 2 – Fuel System

Fuel temperature sensor

5

Fuel filter

6

Fuel tank7

Fuel pump and sender unit8

Denso common rail system

E69808

3 4

Fuel pump1

Fuel rail (common rail)2

Fuel injector3

Lesson 2 – Fuel System

Lesson 2 – Fuel System

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

Lesson 2 – Fuel System Low-pressure system

Fuel line to the fuel pump

The fuel filter clipped onto the transaxle end of the

cylinder head is equipped with an electric fuel heater

There is a water drain screw in the top section of the

filter housing for draining the filter

The fuel filter must be drained of water regularly in

accordance with the service intervals

21

5

76

Battery junction box1

Fuel preheater relay2

Fuse (10A)3

Fuse (15A)4

Ground5

Electric fuel preheater in the fuel filter6

Ground7

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 currenttemperature

Below a fuel temperature of 0 to –4 °C, the circuit isclosed by the bimetal and the heating element thusenergised

The bimetal opens the circuit at a fuel temperature from

1 to 5 °C and ends the heating phase

Bosch common rail system Lesson 2 – Fuel System

System with piezo-controlled fuel injectors

4

5

6 7

1 2 3

4

5

6 7

of a frontal impact

Located on the fuel filter housing is a water drain screw.The fuel filter must be drained via this screw inaccordance with the service intervals

Note:

• Before draining the fuel filter, make sure that thesurrounding components do not come into contactwith the fuel that is drained

There is a thermo valve integrated in the fuel filter for

preheating the fuel.

Lesson 2 – Fuel System Bosch common rail system

How fuel preheating works

1

2 3

4 5

4 5

Thermostat closed7

The fuel filter is equipped with a mechanical fuel

preheater

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

Fuel return temperature < 10 °C:

• The thermo valve is in compressed state

• The bypass to the fuel filter is wide open in this state.The cross section of the fuel return outlet is slightlyopen

• The majority of the returning fuel flows through thewide open bypass into the fuel filter Only a smallpart of the returning fuel can flow back to the fueltank via the slightly open cross section of the fuelreturn outlet

Bosch common rail system Lesson 2 – Fuel 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

• The majority of the returning fuel flows through thewide open fuel return outlet Only a small part of thereturning fuel can flow through the slightly openbypass to the fuel filter

Percentage of fuel to the fuel filter Percentage of fuel to the fuel tank

Fuel return temperature

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

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

Lesson 2 – Fuel System Bosch common rail system

Overview of the high-pressure system

System with "solenoid valve-controlled" fuel injectors

Fuel pump7

Fuel rail (common rail)8

Fuel pressure sensor9

Bosch common rail system Lesson 2 – Fuel System

System with "piezo-controlled" fuel injectors

Fuel pump9

Fuel line10

Set of leak-off pipes with back pressure valve *

11

* 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

Lesson 2 – Fuel System Bosch common rail system

Pump housing6

Bosch common rail system Lesson 2 – Fuel System

CP1H fuel pump

E70770

2 3 4

The following table shows the introduction dates forthe CP1H based on the vehicle

Introduction of CP1H Vehicle

October 2004Fiesta 2002.25 (11/2001-)

February 2005Focus C-MAX 2003.75

(06/2003-)/Focus 2004.75(07/2004-) with 67 kW (90PS)

May 2005Focus C-MAX 2003.75

(06/2003-)/Focus 2004.75(07/2004-) with 82 kW(110 PS)

With the start of tion

produc-Mondeo 2007.5/S-MAX/

Galaxy 2006.5The function of the CP1H fuel pump is essentially thesame as that of the CP3.2

Lesson 2 – Fuel System Bosch common rail system

Flow of fuel through the fuel pump

E51111

5

4 2

6

E

D

C 3 B

To the fuel injectors

Pressure restrictor3

Fuel metering valve4

Overflow throttle valve5

Fuel pump6

Transfer pump7

Fuel filter8

Fuel tank9

Bosch common rail system Lesson 2 – Fuel System

Transfer pump

E51110

2

31

The contact line of the gears forms a seal between theintake side and the delivery side and prevents the fuelfrom flowing back

The delivery quantity is approximately proportional tothe engine speed For this reason, fuel quantity control

9

5

C B

Low engine speeds

Compression spring3

Restrictor4

To the high-pressure chambers5

Lesson 2 – Fuel System Bosch common rail system

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 againstthe compression spring

Increasing engine speeds require increased cooling ofthe fuel pump Above a certain pressure, the fuel pumpcooling bypass is opened and the flow rate through thefuel pump is increased

At high engine speeds (high transfer pump pressure),

the control piston is moved further against thecompression spring The fuel pump cooling bypass isnow fully open (maximum cooling)

Excess fuel is transferred to the intake side of thetransfer pump via the return bypass

In this way, the internal pump pressure is limited to amaximum of 6 bar

High-pressure generation

E51113

9

8 7

3

2 1

4

Bosch common rail system Lesson 2 – Fuel System

High pressure to the fuel rail

High-pressure chamber7

Pump plunger8

Intake valve9

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

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

Fuel is now forced into the high-pressure chamber,

which moves the pump plunger downwards (intake

stroke)

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

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

Zero delivery valve

To the transfer pump4

The zero delivery valve is located between the annularchannel that is connected to the intake valves of thehigh-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 pumppressure As a result, the intake valves are opened and

an undesirable pressure increase may occur in thehigh-pressure system

To prevent this, the zero delivery valve features acalibrated bore In this way, excess fuel is fed back tothe intake side of the transfer pump

Lesson 2 – Fuel System Bosch common rail system

Fuel rail (common rail)

Structure and purpose

E43248

1

Fuel pressure sensor

1

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

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

Fuel pressure sensor

There is a fuel pressure sensor located on the fuel rail

so that the engine management system can preciselydetermine the injected fuel quantity as a function of thecurrent fuel pressure in the fuel rail (see "Lesson 4 –Sensors")

High-pressure fuel lines

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 reasonfor this is that leaks can occur when retightening due todistortion of the connections of the old lines

The high-pressure fuel lines connect the fuel pump tothe fuel rail and the fuel rail to the individual fuelinjectors

Fuel injectors (general)

Depending on the engine type, different fuel injectorsare used:

• solenoid valve-controlled fuel injectors or

• piezo-controlled fuel injectors

Solenoid valve-controlled fuel injectors are installed

in the 1.6L Duratorq-TDCi (DV) diesel engine

Piezo-controlled fuel injectors are installed in the 2.2L

Duratorq-TDCi (DW) diesel engine

Start of injection and injected fuel quantity arecontrolled via the fuel injectors

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

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 thecurrent Service Literature

The fuel injectors are divided into different functionblocks:

E51115

B A

4

3 10

Fuel injector closed

Nozzle prechamber7

Nozzle needle spring8

Valve control piston9

Valve control chamber10

Outlet restrictor11

Bosch common rail system Lesson 2 – Fuel System

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

Fuel injector opens

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

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

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

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 itsbottom stop

Indirect actuation

Indirect actuation of the nozzle needle via a hydraulicbooster system is used because the forces required forrapid opening of the nozzle needle cannot be generateddirectly with the solenoid valve

The "control quantity" therefore required in addition tothe injected fuel quantity enters the fuel return via therestrictors in the control chamber

Leak-off quantities

In addition to the control quantity, there are leak-offquantities at the nozzle needle and valve control pistonguides

These leak-off quantities are also discharged into thefuel return

Service instructions (fuel injector correction factor)

E51116

01

15440 136080F DDFO

760680

38415 015

1724

1

2

Fuel injector1

Correction factor2

Inside the hydraulic servo system there are variousrestrictors with extremely small diameters which havespecific manufacturing tolerances

These manufacturing tolerances are given as part of acorrection factor which is located on the outside of thefuel injector

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 black smoke formation,

• irregular idling,

• 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 nozzleneedles

6

5

1 2

3 4

Fuel injector5

Retaining clip6

Bosch common rail system Lesson 2 – Fuel System

The fuel injectors are mounted on the cylinder head and

protrude into the centre of the individual combustion

chambers

The fuel injectors are opened and closed using a piezo

element The piezo element is located inside the fuel

injector

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

• Realisation of very small injected fuel quantities for

the pilot injection(s)

• Low noise emissions (up to 3 dB)

• Improved fuel economy (up to 3%)

• Lower exhaust emissions (up to 20%)

• Increased engine power output (up to 7%)

• Improved running smoothness

High-pressure connectionb

Piezo element1

Hydraulic coupler2

Control valve3

Nozzle module with nozzle needle4

Spray holes5

Electrical connector6

In the case of the piezo-controlled fuel injector, thenozzle needle is indirectly controlled via a control valve.'Indirectly' means that the nozzle needle is opened andclosed via a hydraulic circuit

The hydraulic circuit comprises a low-pressure and ahigh-pressure part The control valve provides theinterface between the high-pressure and the low-pressureparts

The required injected fuel quantity is controlled via theopening times of the control valve

Lesson 2 – Fuel System Bosch common rail system