Operating Fuel Pump For Test

Fuses and Relays
Both the transfer pump and the main fuel pump are electric, and operated by the fuel pump relay. If neither pump runs, the cause may be a faulty fuse or a faulty fuel pump relay. In cold weather, water in the fuel may freeze in the pump, causing the circuit to overload and the fuse to fail. Begin troubleshooting any fuel pump faults by checking the fuel pump fuse and the fuel pump relay.

Relay and fuse locations vary from model to model and year to year. To identify and locate the components on a particular car, see WIRING DIAGRAMS.

Operating Fuel Pump For Test
Unless the fuel pump relay receives an rpm signal from the ignition system indicating that the engine is running, that fuel pump will operate for only a few seconds when the ignition is On. To power the fuel pump for testing without the engine running, the relay must be bypassed.

To bypass the fuel pump relay, remove it and substitute a remote switch, such as Volkswagen special tool no. US 4480/3 (order no. TU4 480 003 25 ZEL), or a jumper wire between two sockets on the fuse/relay panel. The correct sockets are the two largest ones located perpendicular to each other and corresponding to relay terminals 30 (battery voltage) and 87 (output to fuel pumps). Fig. 4-2 shows the typical locations of these terminals.

The sockets are also identified on the relay panel itself. On 1985-1989 Golf and GTI models, they are sockets 27 and 33. On Jetta models from 1985 to January 1989, they are sockets 2 and 3. On Jetta models from January 1989, and on Golf and GTI models beginning 1990, they are sockets 4 and 6. For information on relay location and terminal identification for a particular model, see WIRING DIAGRAMS.

NOTE: A home-made jumper wire should be at least 1.5 mm (16 ga.) wire and, for safety, should include an in-line fuse holder with a 20 amp fuse. To avoid damaging the relay sockets with frequent connections, the jumper wire should also include a toggle switch for switching on and off.

With the ignition off and the fuel pump relay removed, use the jumper (toggle switch off) to bridge the sockets in the fuse/relay panel. Turn on the toggle switch to operate the fuel pump. If the fuel pump does not run except when the jumper is connected, the relay or relay wiring is faulty. If the pump does not run with the jumper in place of the relay, the fault could be in the fuel pump or the electrical wiring to the fuel pump. For more fuel pump electrical testing, see Fuel Pump Electrical Tests.

Fig. 4-2:

Fig. 4-2. Jumper wire with fuse (shown schematically) used to bypass fuel pump relay and operate fuel pump for test connection between two largest terminal sockets routes battery voltage (terminal 30) directly to the fuel pump circuit (terminal 87) (1985-1988 Golf/GTI relay panel shown, others are similar).