2000 AUDI A6 fuel pump

24-111

Fuel pressure, fuel pressure regulator
and residual fuel pressure, checking

The fuel pressure regulator controls the fuel
pressure depending on intake manifold
pressure.

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

Pressure tester VAG1318
Adapter 1318/7
Adapter 1318/10
Adapter 1318/13

Test requirements
Fuel pump delivery rate OK; checking:
Pa
ge 142 of 166 Motronic Multi
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jection
(MFI
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24-113
If the specified value is not attained:

- Replace fuel pressure regulator and repeat
pressure test.
If the specified value is still not obtained:

- Check fuel pump or supply line for damage (e.g.
pinched locations); replace if necessary.
If the specified value is exceeded:

- Check return line for damage (e.g. pinch
locations); replace if necessary.

- Install vacuum hose on fuel pressure regulator
and check for pressure drop on gauge.

Specification: when vacuum hose is installed,
fuel pressure must drop by about 0.5 bar (7 psi).
If pressure does not change, the following tests
should be conducted:

- Check vacuum line for leaks (cracks,
damage).

-
Check vacuum line at intake hose for
obstruction; remove hose at fuel pressure
Pa
ge 146 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

24-115
If the residual pressure drops (is lower than
spec.) again, the following malfunctions are
possible.

Connections for the pressure gauge and fuel
lines leaking
Pre-feed line on fuel reservoir leaking
Check valve in the electric fuel pump
malfunctioning

Repair Manual, Fuel Supply System, Repair
Group 20, Checking fuel pump check valve

If retaining pressure does not drop, the following
malfunctions are possible:

Malfunctioning fuel pressure regulator
Injectors leaking
Connections for the pressure gauge leaking
behind shut-off valve

Note:
Pa
ge 149 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
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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

24-121

Checking EVAP canister purge regulator
valve voltage supply

Test conditions

Fuse for EVAP canister purge regulator
valve OK

- Disconnect harness connector from EVAP
canister purge regulator valve.

If LED test light does not light:
If wiring is OK: - Connect VAG1527B LED voltage tester between connector terminal 1
(B+) and engine Ground.
- Operate starter motor.
Specified value: LED must light up
- Check wiring for open circuit between connector terminal 1 and fuse,
according to wiring diagram; repair if necessary.

Specified value: 1.0 max.- Check fuel pump relay page 24
-95
.
Pa
ge 158 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

24-124

Leak Detection Pump (LDP), checking


Note:
Component locations page 24
-1

Electrical testing

If resistance is NOT OK: - Disconnect harness connector for LDP -V144-.
- Connect multimeter US1119 (Fluke 83 or equivalent) and check
resistance at leak detection pump. Specified values:

Connector terminal 1 to terminal 3: 640-720

Connector terminal 2 to terminal 3: 11.0-21.0
- Replace leak detection pump -V144-.
Pa
ge 161 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

24-125

Voltage supply, checking

If LED tester does not light: - Disconnect harness connector for LDP -V144-.
- Connect VAG1527B LED voltage tester between connector terminal 3
(B+) and engine Ground.
- Start engine and run engine at idle.
LED must light up.
- Check fuse for LDP -V144-.
- Check wiring for open circuit between terminal 3 and fuse, according to
wiring diagram.

Specified value: max. 0.5 .- Check fuel pump relay and signal to relay page 24
-95
.
Pa
ge 162 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