Mechanical RETURNLESS Fuel System (MRFS) - Single Speed

An output signal from the PCM is used to control the electric fuel pump. The PCM grounds the FP circuit, which is connected to the coil of the fuel pump relay. This energizes the coil and closes the contacts of the relay, sending B+ through the FP PWR circuit to the electric fuel pump. When the ignition is turned on, the electric fuel pump runs for about 1 second and is turned off by the PCM if engine rotation is not detected.

The FPM circuit is spliced into the fuel pump power (FP PWR) circuit and is used by the PCM for diagnostic purposes. With the fuel pump on and the FPM circuit high, the PCM can verify the FP PWR circuit from the fuel pump relay to the FPM splice is complete. It can also verify the fuel pump relay contacts are closed and there is a B+ supply to the fuel pump relay.