Volkswagen Self Study Program 197 – The 2.8L Diesel engine in the LT 1997 SSP-197-The-2-8-l-Diesel-engine-in-the-LT-97
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The 2.8 l Diesel engine in the LT ’97
Design and Function
Self Study Programme No. 197
Page 2
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In the LT ‘97 commercial vehicle series, Volkswagen is adding a
high-performance 2.8 l engine with direct fuel injection to the
Diesel engine line.
In this self study programme we present the new designs and functions
of individual systems of the new Diesel engine.
Page 3
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At a glance
Technical data .............................................................
Overview
Engine - mechanical ..................................................
Cylinder block
Oil circuit
Two-part flywheel
Timing gears
Direct injection
Diesel direct injection .................................................
General overview
Fuel supply
Distributor injection pump
Injection
Fuel cut-off
Speed control
Timing device
Injectors
Boost-pressure enrichment
Fuel filter
Turbocharger
4
6
14
Glow plug system ...................................................... 28
Self check .....................................................................
The Self Study Programme
is not a repair manual!
30
New! Important!
Note!
For information on testing, adjustments
and repairs, refer to the appropriate
customer service literature.
3
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Technical Data
Engine data
Engine code: AGK
Design: 4-cylinder
in-line turbodiesel
engine
Displacement:
Bore: 93 mm dia.
Stroke: 103 mm
Compression ratio: 19 : 1
Rated output: 92 kW (125 HP)
Maximum torque: 280 Nm at
Mixture preparation: Direct injection
100
90
80
70
60
P (kW)
50
40
30
1000
1500
2000
2500 3000
n (1/min)
2798 cm
at 3500 rpm
2200 rpm
with mechanically
controlled distributor
injection pump
3
300
275
250
M (Nm)
225
200
3500
4000
197/1
Oil cooler integrated in
crankcase
Turbocharger
Oil filter
2 coolant thermostat
Vibration damper
for ribbed V-belt
Tensioner for
ribbed V-belt
Vibration damper
197/20
valves
4
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Overview
The 2.8 l turbodiesel engine achieves its maximum
output of 92 kW (125 PS) at 3500 rpm.
The maximum torque of 280 Nm is already available to the engine at a speed of 2200 rpm.
A high torque of more than 250 Nm is available
over the broad speed range of 1750 to 3250 rpm.
This is characterised by excellent tractive power.
The engine is suitable for so-called
bio-Diesel (vegetable-oil methyl ester).
Temperature sender Cylinder order
4321
Intake manifold
Viscous fan
Oil pump
Direct drive with crankshaft
Intake-manifold-dependent
full-load enrichment
Distributor injection pump
Two-part flywheel
Hydraulic pump for power steering
197/48
Cylinder 1 is located at the
flywheel end.
5
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Engine - mechanical
The cylinder block
of the 2.8 l Diesel engine has been keep very „slim“
to reduce noise. The necessary rigidity is achieved
with heavily pronounced ribbing.
Mounting holes for timing gears
197/41
Additional devices are integrated
in the block to reduce noise and
leaks.
Dry cylinder sleeves
Two thermostat valves
Installation opening
for oil cooler
Oil filter mount
Lower crankshaft bearing, separate from crankcase to
reduce noise
197/42
The baffle plate is used to stiffen the
lower cylinder block and to calm the
oil surge.
Baffle plate
197/43
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The oil circuit
is an important system for lubricating sliding metal
parts and for internal engine cooling.
Cylinder order
Jets for piston cooling
Turbocharger
Oil pump, driven
by crankshaft
44
44
33
33
22
22
11
11
Camshaft
Timing gears
FFFFllllyyyywwwwhhhheeeeeeeellll eeeennnndd
dd
Oil pressure
valve
Oil cooler
Pressure relief
valve
Crankshaft
Oil filter
197/35
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Engine - mechanical
The two-part flywheel
On internal-combustion piston engines, torsional
vibrations are produced at the crank-shaft and
flywheel due to the irregularity of the combustion
process.
The two-part flywheel prevents these torsional
vibrations from being transmitted to the drive train,
and from causing resonant vibrations there.
Resonant vibrations are outwardly noticeable as
disturbing noises.
The two-part flywheel divides the flywheel mass into
two parts.
The primary flywheel mass is one part and belongs
to the moment of inertia of the engine. The other
part, the secondary mass, increases the moment of
inertia of the gearbox.
The two isolated masses are connected with a
spring/damping system.
With the moment of inertia of the gearbox components increased in this way, they only absorb
vibrations at considerably lower speeds.
„Gearbox rattling“ in the idling speed range can no
longer occur.
194/024
Vibration damper
8
Crankshaft
group
197/18
Primary flywheel mass of
two-part flywheel
197/45
Vibration isolation
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Ordinary flywheel-clutch design
Flywheel with clutch Clutch disc with
torsion damper
Engine and gearbox vibrations in idling speed
range
194/027194/025
The two-part flywheel
Primary flywheel mass Secondary flywheel mass
with clutch
Torsion damper
(spring/damping system)
Rigid clutch disc
Engine and gearbox vibrations in the idling
speed range
194/028194/026
vibrations produced by the engine
vibrations absorbed by the gearbox
9
Page 10
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Engine - mechanical
Timing gears
The camshaft is driven by the crankshaft with
intermediate gears.
Adjustment bearing
lever
Intermediate gear
(for camshaft drive)
Injection pump
Vane pump
Power steering
Intermediate gear
Cylinder 1 is located on the
flywheel end.
Camshaft sprocket
Intermediate gear
of camshaft
Spacer fork
Intermediate gear
to crankshaft
Coolant pump
Gear group housing
Crankshaft
Valve timing adjustment
To adjust the valve timing, turn the crankshaft to
cylinder 1.
Also turn the camshaft to cylinder 1 (with camshaft
sprocket loosened) and lock in place with the camshaft lock 3445.
10
197/5
Then tighten the camshaft sprocket.
The intermediate gears have no marking for
adjustment.
Page 11
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197/36
The tooth flank adjustment
The tooth flank clearance of the intermediate
camshaft gear can be adjusted.
To adjust, insert the intermediate gear in
the adjustment bearing lever.
Next the intermediate gear is pivoted downward
into the spacer fork with the adjustment bearing
lever.
197/37
Then pivot the intermediate gear with the spacer
fork between the large intermediate gear and the
camshaft sprocket until the specified tooth flank
clearance is achieved.
Then tighten the spacer fork.
This device is patented.
197/38
11
Page 12
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.
Engine - mechanical
Injector
Sheathedelement glow
plug
Direct injection
The new engine is extremely efficient.
197/8
The fuel is injected directly into the main combustion
chamber.
The injector extends into the cylinder combustion
chamber at an angle.
The sheathed-element glow plug is located next to
the injector.
In addition to direct injection, there are two design
characteristics which make this possible.
– Three-valve technology (2 inlet, 1 exhaust valve)
– Inlet ports shaped as swirl ports
Advantages of three-valve technology are:
– Two inlet valves result in a large inlet cross-
section,
– The improved degree of filling of the cylinders.
The design of the inlet ports
197/9
The inlet ports are shaped so that the air flowing in
begins to swirl. This supports the intensive mixing of
air and injected fuel.
This combination with direct injection, three-valve
technology and the swirl port results in intensive
combustion.
The pollutant exhaust gas components are considerably reduced.
The emission values drop far below the legal limits.
12
Page 13
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.
Oil jet
Adjusting the valve clearance
Rocker finger
Adjustment screw
The 2 inlet valves and 1 exhaust valve per cylinder
are actuated by the overhead cam via rocker
fingers.
The rocker finger rests on the adjustment screw on
one side and on the valve on the other side.
The cam runs up against the back of the rocker
finger.
This actuates the valve.
An oil jet lubricates the cam surface, i.e. the oil film
forms a noise cushion.
197/4
197/7
The valve clearance is mechanically adjusted.
Testing and adjustment are carried out with the
engine cold.
A feeler gauge is used to measure the clearance
between the cam surface and the rocker finger.
The adjustment is made with an Allan key by
screwing the self-locking adjustment screw in or out.
The related cam of the cylinder to be
checked must always be facing upward.
Allan key Feeler gauge
13
Page 14
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Diesel direct injection
General overview
The 2.8 l TDI engine operates with
– mechanically controlled, direct injection with a
distributor injection pump
– exhaust-gas turbocharger,
boost pressure pneumatically controlled
with bypass
– boost-pressure-dependent enrichment, pneuma-
tically controlled
– glow plug system, controlled in dependence on
engine coolant temperature
– intercooler for cooling the intake air before it
enters the intake manifold
– pre-heated fuel filter
D = Ignition/starter switch
G62 = Coolant temperature sender
J52 = Glow plug relay
K29 = Glow period warning lamp
Q6 = Glow plugs
Bypass
Exhaust-gas turbocharger
Intercooler
14
Page 15
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Q6
G62
K29
J52
D
Fuel filter
Distributor injection pump Fuel tank
CCCCoooolllloooouuuurrrr ccccooooddddiiiinnnngggg////LLLLeeeeggggeeeennnndd
= Output signal
= Input signal
= Positive
dd
= Fuel supply line
= Fuel return line
= Air
= Exhaust
197/10
15
Page 16
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Diesel direct injection
The fuel supply
The fuel is sucked in directly via the fuel filter from
the fuel tank by the feed pump in the distributor
pump housing.
The fuel is then carried via the high-pressure pump
section of the distributor injection pump to the injectors for injection.
Excessive fuel flows back to the fuel tank via a
return line.
Injector
Pressure line
Distributor injection pump
16
Fuel tank
Return line
Suction line
Fuel filter
197/11
Page 17
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The distributor injection pump
Centrifugal governor
Feed pump
Quantity adjuster for
boost-pressure enrichment
Fuel inlet
Roller ring
piston
Eccentric disc Distributor
Injection distributor High-pressure pump
Fuel cut-off
The high-pressure pump
197/25
197/49
In the high-pressure pump the distributor piston is
moved forward by the eccentric disc and produces
the necessary pressure on the enclosed fuel, which
is carried via the distributor duct to the injectors for
injection.
When replacing the distributor-type fuel
injection pump, the new pump must be
filled with fuel.
17
Page 18
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.
Diesel direct injection
The injection
Filling
Filling hole
Distributor piston
Turn the distributor piston to align the filling
hole with the control slit.
Control slit
The pressurised fuel flows into the high-
197/39
pressure chamber.
Injectors
The distributor piston continues to turn. The control
slit and filling hole are no longer aligned.
The distributor piston is moved forward by the
eccentric disc and the fuel is pressed toward the
injector via the distributor duct.
18
Distributor duct
197/40
Page 19
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The fuel cut-off
Filling hole
High-pressure chamber
Electrical circuit
15
31
Solenoid valve
N109
Spring
Armature
To shut off the engine, the solenoid valve N109
closes off the fuel supply hole.
The solenoid valve consists of a coil and an armature with a pressure spring.
When the ignition is switched on, the coil is supplied
with voltage and pulls in the armature against the
force of the spring.
The armature of the solenoid valve, which simultaneously acts as a check valve, holds open the
filling hole to the high-pressure chamber.
After the ignition is switched off, the voltage supply
is interrupted.
The magnetic field collapses.
The spring presses the armature onto the valve seat.
197/2
The filling hole is closed off.
N109
197/3
The engine stops.
Effects in case of failure
If the solenoid valve is defective or the voltage
supply is interrupted, the engine stops.
19
Page 20
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.
Diesel direct injection
The speed control
The centrifugal governor controls the idling speed
and cuts off the injection quantity at maximum
speed.
Start
With the engine stopped, the leaf spring pushes the
starting lever to the left.
In the process, the control valve moves to the right.
The distributor piston must carry out a long stroke
until the cut-off hole is free.
With this device the starting quantity is increased.
Idling
If the engine is revved-up, the centrifugal weights
move the governor sleeve.
The starting lever is positioned on the tensioning
lever.
This causes the control valve to move to the left.
The cut-off hole is opened above the idling speed.
Control takes place via the idling spring with a
balanced force ratio between the centrifugal force
and the idling spring.
The stroke of the distributor piston is
determined by the eccentric disc.
Leaf spring
Starting lever
Control valve
Distributor piston
Cut-off hole
Starting lever
Centrifugal weights
Control valve
Stroke for start quantity
Idling spring
197/30
Tensioning leve
20
Stroke for idling
197/31
Page 21
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Acceleration/Part throttle
The tensioning lever is pulled to the left with the
drag element.
This causes the control valve to move to the right.
Drag element
The stroke up to the opening of the cut-off hole
becomes greater, thus increasing the injection
quantity.
The engine revs accordingly.
The spring in the drag element still acts as a rigid
connection.
Full throttle - cut-off
When the speed increases further, the forces of the
centrifugal weights also increase.
Control valve
Cut-off hole
Control spring
Stroke for art
throttle
Stop screw
Tensioning lever
197/32
This presses together the control spring in the drag
element.
The control valve moves far to the left so that the
cut-off hole is opened.
As a result, a pressure build-up in the distributor
piston is prevented and the cut-off speed is reached.
Correction lever
Pressure spring
197/33
21
Page 22
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.
Diesel direct injection
The injection distributor
As the engine speed increases, injection must be
advanced.
This task is assumed by the injection distributor.
Injection distributor
The injection distributor has been turned
o
by 90
Roller ring Eccentric disc
for improved illustration.
Roller
197/28
197/44
Pump housing
Roller ring
Roller
197/29
197/50
Function
As the speed increases, the feed pump in the distributor injection pump increases the pressure in the
distributor pump housing.
The increasing pressure also acts on the piston of
the injection distributor.
The piston is deflected and turns the roller right
against the rotating direction of the distributor
piston via the driver.
22
Driver
Piston
The eccentric disc runs up against the cam earlier so
that injection is carried out earlier.
Page 23
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The injectors
are two-spring jets. They spray the fuel directly into
the cylinder in two stages. This results in "soft"
combustion and reduced combustion noise.
Two-spring jet holder
Spring 1
Spring 2
Gap for stroke 2
Gap for stroke 1
Stroke 1
197/23 197/24
Stroke 2
Jet needle
197/22
Function
The injector is designed as a fivehole jet.
There are two springs of different
strengths located in the jet holder.
The springs are matched so that
at the start of injection, the jet
needle is only lifted against the
force of spring 1.
197/46
A small quantity of fuel is preinjected at low pressure through
the resulting small gap.
This pre-injection provides a gentle increase in the combustion
pressure and creates the ignition
conditions for the main fuel
quantity.
As the injection pump feeds more
fuel than can flow through the
small gap, the pressure in the
injector increases. The force of
spring 2 is overcome and the jet
nozzle is lifter further. Now the
main injection is carried out at a
higher injection pressure.
23
Page 24
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Diesel direct injection
The boost-pressure enrichment
adapts the fuel quantity to the air mass.
Full-throttle enrichment
Boost-pressure
valve
Diaphragm
Boost pressure from
intake manifold
Push rod small diameter
Task
Adapt fuel quantity to the air filling of the cylinders:
– more air (due to turbocharging) = ensure high
fuel supply
– reduced air mass = reduce fuel supply
An increasing boost pressure increases the cylinder
filling, and more fuel must be injected accordingly.
This is achieved by adjusting the usable stroke of the
distributor piston.
The adjustment is pneumatic-mechanical.
Control valve
24
Distributor piston
The high boost pressure presses the diaphragms in
the boost-pressure valve downward. The pin resting
on the diaphragm push rod glides from the large to
the small diameter of the push rod.
This causes the control valve on the distributor
piston to be moved to the right via the lever
mechanism.
The usable stroke increases and more fuel is
injected.
197/15
Page 25
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Idling/Part throttle
No enrichment is required at idle and at part
throttle.
The boost pressure is not high enough to overcome
the spring force under the diaphragms.
The spring pushes the diaphragms upward.
The pin is now resting on the large diameter of the
push rod.
Diaphragm
The lever mechanism moves the control valve to the
Push rod large diameter
197/16
left.
This reduces the usable stroke of the distributor
piston.
Less fuel is injected.
25
Page 26
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.
Diesel direct injection
Fuel filter
In the fuel filter mechanical impurities and water are
kept out of the distribution injection pump.
As the specific weight of water is higher than that of
Diesel fuel, water collects in the lower section of the
filter housing.
Water can collect during refuelling or due
to the presence of condensed water in
fuel.
– The water should be drained off in
autumn before the winter period.
– Failure to change the filter at proper
intervals may result in damage to the
distributor injection pump.
The fuel pre-heating
At lower temperatures Diesel fuel tends to separate
out paraffin, which clogs the fuel filter.
To prevent this, the heated fuel flowing back from
the pump is used for „pre-heating“ in the filter.
Depending on the temperature, the bimetal control
valve routes the fuel to the filter again or into the
fuel tank.
At a temperature above +31
valve is in the rest position, and the path to the filter
is closed. The fuel flows to the fuel tank.
At a temperature below +15
o
C the bimetal control
o
C the bimetal control
valve opens the passage to the filter and fuel flows
to the filter.
Bimetal control valve
Return line to fuel tank
Return line from
injection pump
Suction line
Filter
197/12
Water drain screw
Bimetal control valve closed
Bimetal control valve open
197/13
26
197/14
Page 27
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.
The turbocharger
is driven with the exhaust gas to compress the air
required for combustion.
The air quantity per work cycle is increased.
The result is a power increase with the same
displacement and at the same speed.
Waste gate
Bypass
Turb in e
The turbocharger contains a turbine and a compressor impeller on a common shaft.
With these the energy contained in the exhaust gas
is transmitted to the compressor side.
The speed may be over 100,000 rpm.
As the turbocharger speed increases, so does the
boost pressure.
In order not to endanger the life of the engine, the
boost pressure is limited.
This task is assumed by the boost-pressure
Turbocharger
controller.
Compressor impeller
Intercooler
Air cleaner
At a certain boost pressure the boost pressure
controller opens.
Part of the exhaust gas flows past the turbine.
The turbocharger speed drops.
An output increase is also achieved through the use
of an intercooler. The combustion air sucked in by
the turbocharger via the air cleaner is particularly
strongly heated in the turbocharger on the way to
the engine. The air density, and thus the oxygen
content, drop.
In the intercooler it is cooled down again, whereby
the air density increases. Then the air is pressed into
the combustion chamber.
197/17
27
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.
Glow plug system
The AGK engine is equipped with a controlled glow
plug system. The glow plug relay is connected to a
glow period control unit.
If the engine it to be started at low temperature, the
coolant temperature sensor G62 determines the
preheating time.
Preheating is initiated with the ignition/starter switch
D.
It is indicated with the glow period warning
lamp.
When the glow period warning lamp goes out, the
preheating time for starting has been reached.
Preheating is continued for a certain period
after the glow period warning lamp goes out
(ready time).
During this time the engine should be started.
If the engine is not started within the ready time, the
connection on Terminal 50 of the control
unit from the glow plug relay ensures that heating
takes place as long as starting continues.
Following starting a after-glow phase begins.
60
120
80
40
1/1
1/2
0
40
120
100
km/h
km
140
160
180
200
ABS
ABD
SRS
40
30
20
10
50
60
70
12
3
9
6
197/21
80
20
In the after-glow phase, heating takes place for a
few seconds dependent on the temperature. After
glowing supports the warm-up phase, has a positive
effect faultless, low-smoke engine operation and
reduces exhaust emissions, e.g. the emission of
unburned hydrocarbons.
If the engine has not been started within a certain
time, the safety switch-off ends pre-heating.
The glow plug relay with the thermo fuse
for the glow plugs is located on the
auxiliary relay carrier in the engine
compartment at the left.
28
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30
15
30
15
D
5030
50
T6/2 T6/315T6/1
K29
B
J52
T6/6
G62
31
The current flow diagram of the glow plug
system with control unit
T6/4
31
+
1
23 4
S39
80A
A
-
Q6
A = Battery
B = Starter
D = Ignition/starter switch
G62 = Coolant temperature sender
J52 = Glow plug relay
K29 = Glow period warning lamp
S39 = Thermo fuse for engine glow plugs
31
197/26
29
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Self check
Which answers are correct?
Sometimes only one.
But maybe more than one – or even all of them!
Please fill in the blanks.
1. Valve actuation takes place
A. directly with the overhead cam,
B. via rocker arms,
C. via rocker fingers.
2. The timing gears for driving the distributor injection pump and the camshaft are
located on the .............................. .
The cylinders are numbered starting on the .............................. end
3. The tooth flank clearance of an intermediate gear can be adjusted.
It is
A. the intermediate gear for the crankshaft.
B. the intermediate gear of the camshaft.
Adjustment is carried out by pivoting the .................................. .
4. Full throttle enrichment is a measure for adapting the .............................. of the
air filling of the cylinders.
It takes place .............................. .
?
The boost pressure is tapped off at the .............................. .
SSSSeeeellllffff
cccchhhheeeecccckk
kk
30
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.
5. To pre-heat the Diesel fuel,
A. the glow period control is used,
B. the heated fuel flowing back from the pump is used in the filter,
C. engine coolant flows around the filter.
6. The duration of the pre-heating and after-glow period of the glow plugs is
A. manually influenced by operating the starter switch,
B. controlled via a glow period control unit,
C. is determined by the coolant temperature sensor.
7. The control pressure for wastegate is
A. tapped off at the compressor air outlet,
B. tapped off at the intake manifold air outlet,
C. also controlled by the glow plug relay via a solenoid valve.
8. To save space, the .............................. and the ..............................
are integrated in the cylinder block without intermediate lines.
9. Which of the following statements are false?
A. The combination of direct injection, three-valve technology and swirl port
results in intensive combustion.
B. The fuel is injected in 2 stages.
C. The distributor injection pump operates with the full throttle stop
in dependence on the atmospheric pressure.
10. The injector is a .............................. .
?
Injection is carried out directly .............................. above the piston.
Injection in 2 stages is achieved with .............................. in the jet holder.
7. A; 8. oil cooler, thermostat housing; 9. C; 10. 5-hole jet, in the combustion chamber, 2 springs of different strengths
1. C; 2. flywheel end, output; 3. B, spacer fork; 4. fuel quantity, pneumatic-mechanically, intake manifold; 5. B; 6. B, C;
Solutions:
31
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.
Service. 197
Only for internal use. © VOLKSWAGEN AG, Wolfsburg
All rights and technical changes reserved
740.2810.16.20 Published: 08/97
❀ This paper was made from
woodpulp bleached without using chlorine.
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