AUDI A8 1999 D2 / 1.G AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

Fuse for fuel injectors OK
Engine speed (RPM) sensor OK
Fuel pump relay OK
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24-103

Checking signal from ECM

- Disconnect harness connector from cylinder 1 fuel injector.
- Connect VAG1527B LED voltage tester between connector terminals
(to ECM), using adapter cables from VW1594 connector test kit.
- Disconnect harness connectors from fuel injectors for cylinders 2-6.
- Crank starter briefly to check voltage supply for cylinder 1 fuel injector.
LED must flicker.
- Repeat test for fuel injectors for cylinders 2-6.
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24-104
If LED does not flicker:

- Switch ignition off.

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

- Check wiring for open circuits between ECM/test
box and fuel injector harness connectors:


Cyl. 1 fuel injector terminal 2 to ECM/test
box socket 73

Cyl. 2 fuel injector terminal 2 to ECM/test
box socket 80

Cyl. 3 fuel injector terminal 2 to ECM/test
box socket 58

Cyl. 4 fuel injector terminal 2 to ECM/test
box socket 65

Cyl. 5 fuel injector terminal 2 to ECM/test
box socket 72

Cyl. 6 fuel injector terminal 2 to ECM/test
box socket 79
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Specified value: max. 1.5
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24-105

- Check wiring for open circuit between fuel
injector connector terminal 1 and relay panel,
according to wiring diagram.


Specified value: max. 15
- Check wiring for short circuits between wires
and connector terminals.


Specified value:
Fuel injector resistance, checking

If resistance is NOT OK: - Check resistance of individual fuel injectors.

Specified value: 13.5-15.5 - Replace affected fuel injector.
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24-106

Fuel injectors, checking for leakage


WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure.

Required special tools and test equipment

VW1594 connector test kit
VAG1348/3A remote control connection
VAG1348/3-2 adapter cable
VAG1602 fuel analyzer

Test requirement
Fuel pressure regulator OK page 24
-111

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24-107

Checking

- Remove intake air hose between MAF sensor
and intake air noise muffler.

- Remove vacuum hose from Intake Manifold
Tuning (IMT) valve -N156- (change-over valve).

- Remove 5-pin connector from ignition coils, 2-
pin connector from valve for camshaft
adjustment -N208- (bank 2) and 2-pin connector
from camshaft position sensor -G163- (bank 1).

- Disconnect wiring harness from clips on fuel
rail.

- Disconnect fuel rail from intake manifold and remove fuel lines together
with injectors.
- Remove vacuum hose from fuel pressure regulator.
- Remove harness connectors from all injectors.
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24-108

Checking injection amount

- Insert injector to be tested into measuring glass of VAG1602 fuel
analyzer.
- Connect one terminal of injector being tested to engine ground using
test lead from VAG1594.

Note:
This step lets the fuel pump run without the engine running. The closed
throttle position switch must be closed during the test, or the selected fuel
injector will discharge fuel when it is actuated 5 times. - Connect second terminal of injector to B+ using VAG1348/3A remote
control, VAG1348/3-2 adapter wire and an auxiliary wire.
- Conduct output DTM, actuating cylinder 1 injector -N30- page 01
-51

(fuel pump must be running).
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24-109

- Operate remote VAG1348/3A 30 seconds.

Note:
The spray pattern must be the same for all
valves.
Once all three injectors in a single bank have
been checked:

- Place three measuring glasses on even surface
and check volume.

Specified volume per injector: 90-125 ml
If the measured volume of one or more injectors
is below or above the specified volume:

- Replace malfunctioning injector

- Repeat test to injectors in second bank of
cylinders.
If the measured volumes for all injectors are
under or over the specified volume:

- Check fuel pressure page 24
-111
.
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24-110

Checking for leaks

- Conduct output DTM, actuating cylinder 1
injector -N30- page 01
-51
(fuel pump must be
running).

Note:
This step lets the fuel pump run without the
engine running. The closed throttle position
switch must be closed during the test, or the
selected fuel injector will discharge fuel when it is
actuated 5 times.

- Visually check injector for leaks.

With fuel pump running, only 1 to 2 drops can
drip in a minute (per injector).
If fuel loss is greater:

- Replace leaking injector
Installation of the injectors is in reverse order of
removal.

- Replace O-rings on all injectors and coat O-rings
lightly with clean engine oil.

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jection
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