Fuel Pump Relay: Description and Operation

Description:

CIRCUIT DESCRIPTION
When the ignition is first turned On, the PCM energizes the fuel pump relay which applies power to the fuel pump control module.

Based on engine fuel demand, the PCM sends a signal to the fuel pump control module to change the fuel pump control module voltage output. The fuel pump will then pressurize the fuel system. The fuel pump relay will remain On as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present the PCM de-energizes the fuel pump relay within two seconds after the ignition is turned On, or the engine is stopped. During high engine load situations, the PCM commands the fuel pump to run at high speed.