Fuel Pump (Applications Using Fuel Pump Relay For Fuel Pump ON/OFF Control)
Fuel Pump (FP) is a PCM output signal that is used to control electric fuel pump. With PCM power relay contacts closed, Vehicle Power (VPWR) is sent to coil of fuel pump relay. For electric fuel pump operation, PCM grounds FP circuit, which is connected to coil of fuel pump relay. This energizes coil and closes contacts of relay, sending Battery Voltage (B+) through FP PWR circuit to electric fuel pump. When ignition switch is turned to ON position, electric fuel pump runs for about one second, but is then turned off by PCM if engine rotation is not detected. For applications with 2-speed fuel pumps, a normally closed low speed fuel pump relay is wired into fuel pump ground circuit. With low speed fuel pump relay contacts in normally closed position, there is no extra resistance in ground circuit, allowing high speed operation. For low speed fuel pump operation, PCM will ground Low Fuel Pump (LFP) circuit, which opens relay contacts, causing fuel pump ground circuit to pass through a resistor. (Scheme 18) For additional fuel pump information, see FUEL DELIVERY under FUEL SYSTEMS (GASOLINE).
Scheme 18
Fuel Pump Driver Module Applications & Applications With Fuel Pump Functions Incorporated In Rear Electronic Module)
Note. On LS and Thunderbird, FPDM functions are incorporated in Rear Electronic Module (REM). Fuel pump operation is same as applications using stand-alone FPDM. REM will communicate diagnostic information through Standard Corporate Protocol (SCP) BUS (+) and BUS (-) circuits, instead of using a Fuel Pump Monitor (FPM) circuit.
Fuel Pump (FP) signal is a duty cycle command sent from PCM to Fuel Pump Driver Module (FPDM). (Scheme 19) FPDM uses FP command to operate fuel pump at speed requested by PCM or to turn pump off.
