Audi Workshop Service and Repair Manuals

Voltage is supplied to the fuel pump and some injection system components via the fuel pump relay (J17).

The condition for the closing of the fuel pump relay (J17) is that the engine should be turning. i.e. the relay is only connected to earth (via the engine control unit) when engine speed pulses are detected in the engine control unit.

Test conditions

• ● Battery voltage OK.

Functional testing of fuel pump relay

• ‒ Start actuator diagnosis and activate an injector .

• → The fuel pump relay (central electrics, relay position 6) must pick up ...

• ‒ If the relay does not pick up, test activation of fuel pump relay

• ... and the fuel pump must run.

• ‒ If the fuel pump does not run, check activation for fuel pump and components
  

Checking actuation of fuel pump relay

• ‒ Switch off ignition.

• ‒ Connect test box V.A.G 1598/22 to wiring harness for engine control unit
  => Page 24-6.
• ‒ Connect together sockets 4 and 2 on the test box using an auxiliary cable from V.A.G 1594.
• ‒ Switch the ignition on.

• → Specification: The fuel pump relay (central electrics, relay position 6) must pick up ...

If the relay pulls now, but not during final control diagnosis:

• ‒ Renew engine control unit

If the relay does not pull:

• ‒ Switch off ignition.
• ‒ → Remove fuel pump relay from relay base (central electrics, relay position 6).
• ‒ Connect the multimeter to contact 2 of relay socket and earth to measure voltage.

• ‒ Switch the ignition on.

• 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:

• ‒ Switch off ignition.

The following wiring connections should be checked for open circuits and/or short to positive or negative.

• ‒ Rectify any open/short circuit as necessary.

If no wiring fault is detected:

• ‒ Renew the fuel pump relay (J17).

Checking actuation of fuel pump and components

• ‒ → Withdraw the fuses 28, 29 and 34.
• ‒ Start actuator diagnosis and activate an injector => Page 01-44.
• ‒ Connect the multimeter for voltage measurement to the left-hand and right-hand contacts of the following fuses:

If the specification is not obtained:

• ‒ Check the wiring.

=> "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

If no wiring fault is detected:

• ‒ Renew the fuel pump relay (J17).