AUDI A8 1995 D2 / 1.G ATQ Engine Motronic Injection System Servicing Service Manual

24-34

- Start engine and let run at idle.

The following malfunction are possible if the pressure does not drop:
Repair Manual, Fuel Supply System, Repair Group 20; Fuel supply
-
Front Wheel Drive or fuel supply
- All Wheel Drive

Note:
Pressure gauge displays the pressure behind the stopcock "intake
manifold side" after the stopcock is closed (in direction of fuel injector, fuel
pressure regulator). If the pressure drops in front of the stopcock (in
direction of fuel tank), the device cannot detect it. For this reason, the
center of this page states "If the pressure does not drop...". - Wait until pressure has dropped, and then switch off ignition.
Simultaneously close shut-off valve of VAG1318 pressure gauge (lever
perpendicular to direction of flow -arrow-).
There is a leak in the threaded connection between the pressure
gauge and the fuel supply line There is a leak at the supply line at fuel tank.There is a leak in the check valve in the Fuel Pump (FP).
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The following malfunctions are possible if the
pressure drops again:

Fuel pressure regulator faulty
Fuel injectors not properly sealed
Threaded connections of pressure gauge
behind stopcock is not properly sealed.

Note:
Close stopcock for removing the pressure gauge,
loosen threaded connection at VAG1318/15
adapter and let excess fuel escape into catch
reservoir by opening stopcock.
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Fuel injectors, checking

Special Tools and Equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
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Checking internal resistance

- Remove engine cover (arrows).
- Disconnect harness connector at the fuel injector to be tested.

With an engine at operating temperature, the resistance increases by
approx. 4 to 6 .
If specified value is not obtained: - Connect multimeter at valve for resistance measurement.

Specification: 13.5 to 15.5
- Replace fuel injector Page 24
-43
.
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Checking voltage supply

Test requirements:

Fuel Pump (FP) OK, checking Page 24
-
49
.

Fuse for fuel injectors OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

- Disconnect harness connector at the fuel
injector to be tested.

If LED does not light up: - Connect VAG1527B voltage tester as follows:Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

LED must light up.
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Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Check wire connection between terminal 1 and fuse for injector valves
for open circuit:
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- Repair open circuit if necessary.
If LED lights up:

Checking activation

Test requirement:

Internal resistance of valve OK

Note:
Voltage testers do not go out completely during low current pick-up
between activations by the ECM, but rather continue to glow a little and
then get slightly brighter during activation. - Slide back rubber grommet of fuel injector connector (arrow), but leave
connector connected.
- Connect VAG1527B voltage tester between sockets 2 (signal) and 1
(B+).
- Operate starter briefly (engine can also start).

LED must blink.
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24-40
If LED does not blink:

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

If wire connection is OK: - Check the following wire connections for open circuit and short circuit
to Ground (GND) and B+: Cylinder
Fuel injector harness connector
Terminal
VAG1598/31 test box
Socket
1 2 96
2 2 112
3 2 88
4 2 97
5 2 113
6 2 89
- Repair open circuit or short circuit if necessary.
- Replace Engine Control Module (ECM) Page 24
-21
.
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Fuel rail with fuel injectors, disassembling
and assembling

1 -
Fuel distributor
2 -
to T-piece
3 -
Retaining clip
Check for secure fitting
4 -
O-ring Removing and installing Page 24
-43
Always replaceCoat with clean engine oil
5 -
Fuel pressure regulator
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6 -
O-ring
Removing and installing Page 24
-43
Always replaceCoat with clean engine oil
7 -
Fuel injectors -N30- through -N33-
,Cylinder 5/6 Fuel Injector -N83-, -N84- Removing and installing Page 24
-43
8 -
Retaining clip
Make sure clip is correctly seated on fuel
injector and fuel rail
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