1999 AUDI A8 fuel

24-35
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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24-36


Fuel injectors, checking

Special Tools and Equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
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24-37

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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24-38

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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24-39

- 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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24-41


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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24-42


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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jection s
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