1996 AUDI A8 checking

24-99

Checking fuel pump relay voltage supply and
actuation

- Remove fuel pump relay -J17- from relay panel
position 6.

Checking fuel pump relay voltage supply

- Switch ignition on.

If voltage is NOT OK: - Connect multimeter US1119 (Fluke 83 or similar) and check for voltage
at relay socket:

Terminals 28 (B+) and 34
Terminals 32 (B+) and 34
Specified values: approx. Battery Positive Voltage (B+)
- Repair wiring according to applicable wiring diagram.
Pa
ge 127 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-100

Checking fuel pump relay actuation

Note:
The LED light will light dimly before and after cranking the starter.
If the LED test light does not light up while cranking the starter, check
wiring as follows. - Connect VAG1527B LED voltage tester between relay socket terminals
28 (B+) and 29.
- Briefly crank starter.
LED test light must light up.

If resistance is NOT OK:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder. - Connect VAG1598/22 test box to ECM harness connector page 01
-
67
. (Numbers marked on ECM connector match those on test box).
- Connect multimeter US1119 (Fluke 83 or equivalent) to check for open
circuit between relay socket terminal 29 and test box socket 4.

Specified value: max. 1 - Repair wiring using applicable wiring diagram.
Pa
ge 128 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-102

Fuel injectors, checking


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.
Activating fuel injectors via output Diagnostic
Test Mode (DTM) page 01-51


Required special tools and test equipment

VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VAG1527B LED voltage tester
VW1594 connector test kit
Wiring diagram

Test requirements

Pa
ge 130 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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.
Pa
ge 132 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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.
Pa
ge 135 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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

Pa
ge 136 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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.
Pa
ge 137 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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).
Pa
ge 138 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1