Fuel Pump Relay: Description and Operation

The fuel pump relay is located in the relay holder under the dashboard adjacent to the steering wheel. The relay supplies the fuel pump and oxygen sensor preheaters.

The fuel pump relay is controlled via the anti-theft alarm's engine control module from pin 56 of the Trionic engine control module. Grounding pin 56
causes the relay to operate.

If the ignition has been switched off for longer than 15 minutes, the fuel pump relay will operate for 2 seconds when the ignition switch is turned to the ON position. The purpose of this is to build up the fuel pressure prior
to pre-injection, which takes place when the crankshaft
starts to rotate.

The fuel pump relay then operates as soon as the ECM receives pulses from the crankshaft position sensor.