1998 AUDI A8 engine

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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24-43

Fuel injectors, removing and installing


- Remove engine cover (arrows).
- Remove intake air hose between Mass Air Flow (MAF) sensor and
intake air elbow.
- Remove all harness connectors to injectors.
- Disconnect vacuum hose from fuel pressure regulator.
- Expose wires at fuel distributor.

WARNING!
Fuel system is under pressure! Place a cloth around the connection
point before opening system. Then release pressure by carefully
loosening connection point. - Unscrew fuel distributor from intake manifold (arrows) .
- Remove fuel distributor with injectors from intake manifold
simultaneously upward and set aside in rear of engine compartment on
a clean cloth.
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24-44

- Disengage retaining clip and remove fuel
injector.

Note:
Fuel lines must be disconnected before replacing
fuel distributor.
Installation is reverse of removal, noting the
following:

Remove O-rings at all opened connections.
(Never remove plastic cap from valve head
to replace front O-ring - pry O-ring off over
plastic cap).
Lightly lubricate O-rings with clean engine
oil.
Make sure fuel injectors are in place and
seated correctly
Check clip for unobstructed fitting.
Place fuel rail with secured fuel injectors
onto intake manifold, and apply uniform
pressure to press it in.

Tightening torque
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24-47

Checking Proper Seal

- Check proper seal of fuel injectors (visual
inspection). With Fuel Pump (FP) running, only 1
to 2 drops per minute may drip out per injector.

- If fuel loss is greater, stop Fuel Pump (FP) from
running (disconnect cable bridge) and replace
faulty fuel injector Page 24
-43
.

Checking Injection Quantity

- Insert fuel injector to be tested in a measuring glass from VAG1602
injection quantity test device.

- Connect one terminal of fuel injector to engine Ground (GND) using an
adapter cable and an alligator clip from VAG1594A connector test kit.
- Connect the second terminal of fuel injector to B+ using VAG1348/3A
remote control, VAG1348/3-2 adapter cable and assisting cable.
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24-50
Voltage is supplied to the Fuel Pump (FP) and
several components of the injection system via
the Fuel Pump (FP) relay -J17-.
Engine must be turning for Fuel Pump (FP) relay
-J17- to close. This means that the relay does
not receive Ground (GND) (via ECM) until the
ECM recognizes RPM signals.

Note:

Fuel Pump (FP) relay is located at position 4 of central electrics in driver's
footwell, left.
Test requirement:
Battery voltage at least 12.7 V
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