AUDI 1.9 TDI Service Manual
Service.
Self-Study Programme 209
1.9-ltr. TDI Engine with
Pump Injection System
Design and Function
1
Something new has happened to the diesel engine
The demands on the modern diesel engine with
regard to performance, fuel economy, exhaust
emissions and noise levels are growing
constantly.
Good mixture preparation is a key factor for
meeting these requirements.
This calls for efficient injection systems which
produce high injection pressures to ensure that
fuel is atomised very finely. Also, it is necessary to
precisely control the commencement of fuel
injection and injection quantity.
This is how it might have looked:
The pump injection system meets these tough
requirements.
Even Rudolf Diesel thought about combining the
injection pump and injector in one unit in order to
dispense with high-pressure lines and thereby
achieve high injection pressures. However, he did
not have the technical means to put this idea into
practice.
In 1905, Rudolf Diesel came up with the idea of a
pump injector.
Diesel engines with mechanically controlled
pump injection systems have been in use in ships
and trucks since the 1950s.
For the first time, Volkswagen, in association with
Robert Bosch AG, has succeeded in developing a
diesel engine with a solenoid valve controlled
pump injection system suitable for use in
passenger cars.
The Self-Study Programme
is not a Workshop Manual.
Please always refer to the relevant Service Literature
for all inspection, adjustment and repair instructions.
209_03
A step into the future, this engine meets the tough
demands on performance and clean emissions.
At this rate, Rudolf Diesel's vision of "smokeand odour-free exhaust gases“ will one day
become reality.
New
Important
Note
Table of contents
Introduction ..................................................................
Specifications
Pump injection system .................................................
General
Structural design
Driving mechanism
Injection cycle
Fuel supply ...................................................................
Diagram of fuel circuit
Fuel pump
Distributor pipe
Fuel cooling system
4
6
18
Engine management ...................................................
System overview
Sensors
Actuators
Glow plug system
Function diagram
Self-diagnosis
Engine mechanicals ....................................................
Trapezoidal piston and conrod
Toothed belt drive
Service ...........................................................................
Special tools
26
51
54
3
Introduction
1.9-ltr. TDI engine with pump injection system
It was developed on the basis of the 1.9-ltr./
81kW TDI engine with no intermediate shaft.
Only through the injection system does it differ
from the engine fitted with a distributor
injection pump.
On the following pages we will explain
everything about the design and the mode of
functioning of the pump injection system and
we will show you the necessary modifications
to the fuel system, engine management system
and engine mechanicals.
209_05
The diesel engine with the pump injection system
has the following advantages over the distributor
injection pump:
Low combustion noise•
Clean emissions•
These advantages are attributable to:
The high injection pressures of up to 2050 bar
•
Precise control of the injection cycle
•
Low fuel consumption•
High efficiency•
The pre-injection cycle•
4
Specifications
Engine code:
Type:
Stroke/bore:
Compression ratio:
Mixture preparation
Engine management:
Fuel type:
AJM
4-cylinder in-line engine
79.5mm/ 95.5mm
18 : 1
Electronic Diesel Control,
Bosch EDC 15 P
Diesel, at least 49CN,
or biodiesel (RME)
Exhaust gas
aftertreatment:
Exhaust gas recirculation
and oxidation catalytic
converter
Output and torque curve
Power output
85 KW
300
Torque
Nm
285 Nm
kW
The engine conforms to exhaust
emission level D3.
Comparative torque curve
Torque
Nm
300
80
250
250
200
150
100
1000 3000
0
2000 4000 5000
Engine speed (rpm)
70
60
50
40
209_06
Thanks to the high injection pressures up to 2050
bar and the favourable effect they have on the
combustion process, the engine develops 285Nm
of torque at only 1900rpm.
Maximum power output is 85kW at 4000rpm.
200
150
100
80
2000 4000 60000
Engine speed (rpm)
1.9-ltr. 85kW TDI engine
1.9-ltr. 81kW TDI engine
209_11
From the same displacement, the engine with
pump injection system develops 21% more
torque than the 1.9-ltr. 81kW TDI engine with
distributor injection pump.
5
Pump injection system
General information
What is a pump injector?
A pump injector is, as the name already implies,
an injection pump combined with a control unit
and an injector.
Just like a distributor injection pump with
injectors, the pump injection system has the
following tasks:
Generating the high injection pressures
•
required
Injecting fuel in the correct quantity and at
•
the correct point in time
Each cylinder of the engine has a pump injector.
This means that there is no longer any need for a
high-pressure line or a distributor injection pump.
Pressure
generating
pump
Injector
6
Control unit
(solenoid valve)
209_12
Fitting location
The pump injector is directly
integrated in the cylinder head.
Fixing
209_86
It is attached to the cylinder head by a clamping block.
It is important to ensure that the pump injector is
installed in the correct position.
If the pump injector is not perpendicular to the
cylinder head, the fastening bolt can come
undone. The pump injector and/or the cylinder
head may be damaged as a result. Please
observe the instructions given in the Workshop
Manual.
209_87
7
Pump injection system
Design
Roller-type
rocker arm
Ball pin
Injection cam
High-pressure chamber
Pump piston
Piston spring
Solenoid valve
needle
Injector
solenoid valve
Fuel return line
Retraction piston
Fuel supply line
O-rings
Injector
spring
Injector needle
damping element
Heatinsulating seal
209_23
Cylinder head
Injector
needle
8
Drive mechanism
The camshaft has four additional
cams for driving the pump injector.
They activate the pump pistons of
the pump injector via roller-type
rocker arms.
Injection cam
Valve cam
Roller-type
rocker arm
The injection cam has a
steep leading edge. . .
As a result, the pump piston is pushed down at
high velocity and a high injection pressure is
attained quickly.
Roller-type rocker arm
209_15
. . . and a flat trailing edge.
As a result, the pump piston moves up and down
slowly and evenly, allowing fuel to flow free of
air bubbles into the high-pressure chamber of
the pump injector.
Roller-type rocker arm
Injection cam
Pump
piston
Injection cam
209_16 209_17
Pump
piston
9
Pump injection system
Requirements relating to mixture formation and combustion
Good mixture formation is a vital factor to ensure
efficient combustion.
Accordingly, fuel must be injected in the correct
quantity at the right time and at high pressure. Even
minimal deviations can lead to higher levels of
pollutant emission, noisy combustion or high fuel
consumption.
Pre-injection cycle
To ensure the combustion process is as soft as
possible, a small amount of fuel is injected at a low
pressure before the start of the main injection cycle.
This injection process is known as the pre-injection
cycle. Combustion of this small quantity of fuel causes
the pressure and temperature in the combustion
chamber to rise.
A short firing delay is important for the combustion
sequence of a diesel engine. The firing delay is the
period between the start of fuel injection and the start
of pressure rise in the combustion chamber. If a large
fuel quantity is injected during this period, the
pressure will rise suddenly and cause loud
combustion noise.
This meets the requirements for quick ignition of the
main injection quantity, thus reducing the firing delay.
The pre-injection cycle and the "injection interval"
between the pre-injection cycle and the main injection
cycle produce a gradual rise in pressure within the
combustion chamber, not a sudden pressure build-up.
The effects of this are low combustion noise levels and
lower nitrogen oxide emission.
Main injection cycle
The key requirement for the main injection cycle is the
formation of a good mixture, the aim being to burn
the fuel completely if possible. The high injection
pressure finely atomises the fuel in such a way that the
fuel and air can mix well with one another. Complete
combustion reduces pollutant emission and ensures
high engine efficiency.
The injection curve of the pump injection system largely
matches the engine's demands, with low pressures
during the pre-injection cycle, followed by an "injection
interval", then a rise pressure during the main injection
cycle. The injection cycle ends abruptly.
End of injection
At the end of the injection process, it is important that
the injection pressure drops quickly and the injector
needle closes quickly. This prevents fuel at a low
injection pressure and with a large droplet diameter
from entering the combustion chamber. The fuel does
not combust completely, giving rise to higher pollutant
emissions.
Pump injectorEngine demand
Injection
pressure
Time
10
The injection cycle
The high-pressure chamber is filled
Roller-type rocker arm
During the filling cycle, the pump piston moves
upwards under the force of the piston spring and
thus increases the volume of the high-pressure
chamber.
The injector solenoid valve is not activated.
The solenoid valve needle is in its resting position
and opens up the path from the fuel supply line
to the high-pressure chamber. The fuel pressure
in the supply line causes the fuel to flow into the
high-pressure chamber.
Pump piston
Piston spring
High-pressure
chamber
Solenoid valve needle
Injector
solenoid valve
Fuel supply line
209_24
11
Pump injection system
The injection cycle
The pre-injection cycle commences
The injection cam pushes the pump piston down
via the roller-type rocker arm and thus displaces
fuel out of the high-pressure chamber into the
fuel supply line.
The engine control unit initiates the injection
cycle by activating the injector solenoid valve. In
the process, the solenoid valve needle is pressed
down into the valve seat and closes off the path
from the high-pressure chamber to the fuel
supply line. This initiates a pressure build-up in
the high-pressure chamber. At 180 bar, the
pressure is greater than the force of the injector
spring. The injector needle is lifted and the preinjection cycle commences.
Pump piston
Solenoid valve
seat
Injection cam
High-pressure
chamber
Solenoid valve needle
Fuel supply line
Injector needle
209_25
12
The pre-injection cycle commences
Injector needle damping
During the pre-injection cycle, the stroke of the injector
needle is dampened by a hydraulic 'cushion'. As a result, it is
possible to meter the injection quantity exactly.
This is how it works:
In the first third of the total stroke, the injector needle is
opened undamped. The pre-injection quantity is injected into
the combustion chamber.
As soon as the damping piston plunges into the bore in the
injector housing, the fuel above the injector needle can only
be displaced into the injector spring chamber through a
leakage gap. This creates a hydraulic 'cushion' which limits
the injector needle stroke during the pre-injection cycle.
Undamped
stroke
209_35
Injector spring
chamber
Injector housing
Leakage gap
Hydraulic
cushion
Damping piston
209_36
13
Pump injection system
The injection cycle
End of pre-injection cycle
The pre-injection cycle ends straight after the
injector needle opens. The rising pressure causes
the retraction piston to move downwards, thus
increasing the volume of the high-pressure
chamber.
The pressure drops momentarily as a result, and
the injector needle closes.
This pre-injection cycle now ends.
The downward movement of the retraction piston
pre-loads the injector spring to a greater extent.
To re-open the injector needle during the
subsequent main injection cycle, therefore, the
fuel pressure has to be higher than during the
pre-injection cycle.
Pump piston
High-pressure
chamber
Injector
solenoid valve
Retraction
piston
Injector
spring
Injector needle
209_26
14
The injection cycle
The main injection cycle commences
The pressure in the high-pressure chamber rises
again shortly after the injector needle closes.
The injector solenoid valve remains closed and
the pump piston moves downwards.
At approx. 300 bar, the fuel pressure is greater
than the force exerted by the pre-loaded injector
spring. The injector needle is again lifted and the
main injection quantity is injected.
The pressure rises to 2050 bar, because more
fuel is displaced in the high-pressure chamber
than can escape through the nozzle holes.
Maximum. fuel pressure is at max. engine output,
i.e. at a high engine speed with a large quantity
of fuel being injected at the same time.
Pump piston
High-pressure
chamber
Injector
solenoid valve
Injector
spring
Injector needle
209_27
15
Pump injection system
The injection cycle
The main injection cycle ends
Solenoid valve spring
The injection cycle ends when the engine control
unit stops activating the injector solenoid valve.
The solenoid valve spring opens the solenoid
valve needle, and the fuel displaced by the
pump piston can enter the fuel supply line. The
pressure drops. The injector needle closes and
the injector spring presses the bypass piston into
its starting position.
The main injection cycle now ends.
Pump piston
Solenoid valve needle
209_28
Injector
solenoid valve
Retraction
piston
Fuel supply line
Injector needle
16
Fuel return in the pump injector
The fuel return line in the pump injector has the
following task:
Cool the pump injector. For this purpose, fuel
•
from the fuel supply line is flushed through
the pump injector ducts into the fuel return
line.
Discharge leaking fuel at the pump piston.
•
Separate vapour bubbles from the fuel
•
supply line via the restrictors in the fuel return
line.
Leaking fuel
Restric-
tors
Pump piston
Fuel return line
Fuel supply line
209_96
17
Fuel supply
The fuel system
A mechanical fuel pump sucks the fuel out of the
fuel tank through the fuel filter and pumps it
along the supply line in the cylinder head to the
pump injector units.
The fuel which is not required for injection is
returned to the fuel tank via the return line in the
cylinder head, a fuel temperature sensor and a
fuel cooler.
The fuel temperature sensor
The fuel cooler
cools the returning fuel to protect the
fuel tank against excessively hot fuel.
determines the temperature of the fuel in
the fuel return line and sends a
corresponding signal to the engine control
unit.
18
The fuel tank
209_18
The fuel filter
protects the injection system
against contamination and wear
caused by particles and water.
The non-return valve
prevents fuel from the fuel pump
flowing back into the fuel tank while
the engine is not running (opening
pressure=0.2 bar).
Loading...