Fuel Pump Relay: Description and Operation

Relay module






The engine management system employs a relay module, which houses the main relay and the fuel pump relay.

Main relay
The main relay supplies the power feed to the ECM with a tap off to feed the fuel injectors (8 amps) and air flow sensor (4 amps). This relay is controlled by the engine management ECM. This enables the ECM to remain powered up after ignition is switched off. During this 'ECM power down routine' the ECM records all temperature readings and powers the stepper motor to the fully open position. Failure of this relay will result in the engine management ECM not being switched on resulting in engine not starting due to absence of fuel and ignition.

Fuel pump relay
The fuel pump relay is fed from the ignition relay and controlled by the engine management ECM. The relay is activated in ignition key position 2 to prime the fuel system for a period of time controlled by the ECM. Failure of this relay will result in no fuel pressure.