Audi Workshop Service and Repair Manuals

Testing for leaks

When there is no electrical supply, solenoid valve remains closed.

• ‒ Disconnect hoses from ACF solenoid valve -N80
• ‒ Connect plug to solenoid valve
• ‒ Start final control diagnosis and actuate ACF solenoid valve -N80 =>Page 01-45.
• ‒ While final control diagnosis is running, blow into solenoid valve to check whether it opens and closes properly. If necessary, fit a new solenoid valve.

Electrical test of -N80 (ACF valve)

• ‒ Pull connector off ACF valve.
• ‒ → Measure resistance between the valve contacts using hand-held multimeter V.A.G 1526.

Specified value: 22...30ω.

• ‒ If the value is not as specified, fit a new ACF valve.

Testing power supply to ACF valve

Note:

The ACF valve receives its power supply via the fuel pump relay.

Test requirements:

• ◆ Fuse -S29 OK

• ‒ Pull connector off ACF valve.
• ‒ → Connect diode test lamp V.A.G 1527 between engine ground and contact 1 on the connector.

• ‒ Operate starter.

Specified value: The diode test lamp should light up.

• ‒ If the diode test lamp does not light up, test for continuity in the wiring between contact 1 and fuse -S29 according to the current flow diagram - if necessary repair open circuit.
• ‒ If wiring is OK, test fuel pump relay =>Page 24-31.

Testing ACF solenoid actuation

• ‒ → Connect the V.A.G 1527 diode test lamp between contact 2 and contact 1 (positive) of the connector.
• ‒ Start final control diagnosis and actuate ACF solenoid valve 1 -N80 =>Page 01-45.
  Specified value: Diode test lamp should flash.
• ‒ If the diode test lamp does not flash or it lights up permanently, connect test box V.A.G 1598/19 to wiring harness for Motronic control unit.

• ‒ → Check wiring between contact 2 of the connector ...

• ‒ → ... and contact D4 on the Motronic control unit for continuity or short to positive and repair as necessary.
• ‒ If no wiring fault is present, replace the Motronic control unit.