Testing fuel pump relay -J17 and relay activation: Audi 2.8 (APR, AQD)

APR
The fuel pump and some of the injection system components are powered via the fuel pump relay -J17.

The fuel pump relay -J17 will only close if the engine is turning over. In other words, the relay is only earthed (via the engine control unit) when the engine control unit is receiving engine speed impulses.

Test conditions

Battery voltage OK.

Functional test of fuel pump relay

Note:

The fuel pump relay is located in the electronics box in the front passenger's footwell (central electrics unit, relay position 4).

Connect vehicle diagnostic, testing and information system VAS 5051 (or fault reader V.A.G 1551) and select engine electronics control unit by entering address word "01" ( => Page
01-3
.)
When doing this the ignition must be switched on.

Start final control diagnosis => Page
01-39
. The fuel pump must be running.

The fuel pump relay should pick up and the fuel pump should run.

If the relay does not pick up:

Test activation of fuel pump relay=>Page
24-42
.

If fuel pump does not run:

Test activation of fuel pump and other components =>Page
24-44
.

Testing activation of fuel pump relay

Switch off ignition.
Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
=> Page
24-14
.
Connect sockets 65 and 2 of test box to each other using auxiliary cable from V.A.G 1594.

Specification: the fuel pump relay (relay position 4) should pick up.

If the relay picks up now but not during the final control diagnosis:

Replace engine control unit =>Page
24-17
.

If the relay does not pick up:

Disconnect fuel pump relay from relay panel (relay position 4).

Connect hand-held multimeter (voltage measurement range) between earth and contact 19 on relay panel.

Specification: approx. battery voltage

If the specification is not obtained:

Check the wiring.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If the specification is obtained:

Test for open circuit and short to positive or earth in the following wiring connections:

Micro central electrics in passenger's footwell (right), relay position 4 / Contact · Test box V.A.G 1598/31 / / / Socket
16 · 65

Rectify any open/short circuit as necessary.

If no fault in wire is detected:

Fit a new fuel pump relay -J17.

Testing activation for fuel pump and other components

Remove fuse cover on A-pillar in footwell on right side.

Pull out fuses 1, 2 and 3 (in blue fuse carrier, 4th row from the top).
Start final control diagnosis => Page
01-39
.
Connect hand-held multimeter (voltage measurement range) between earth and either left or right contact of the following fuses (only one fuse contact is live):

Fuse No. · Specification for left or right contact
1 · approx. battery voltage
2 · approx. battery voltage
3 · approx. battery voltage

If the specifications are not obtained:

Check wiring

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If no fault in wire is detected:

Fit a new fuel pump relay -J17.