Fuel Pump: Description and Operation

OPERATION
PCM controls the fuel pump through the fuel pump relay ground.
- When the key is in START or RUN position and the PCM is receiving an ignition reference signal, the PCM grounds the fuel pump relay, activating pump.
- If no ignition signal is sensed by the PCM, the PCM interrupts relay ground, turning pump off.

CIRCUIT OPERATION
The fuel pump motor, located in the fuel tank, is controlled by the fuel pump relay located in the Power Distribution Center (PDC). Power for the coil side of the relay is provided by circuit F12. The F12 circuit is HOT in the START and RUN position only and protected by a 10 Amp fuse located in cavity 10 of the PDC.

Circuit A21 is used to power the fuse and is connected between the ignition switch and the PDC. Power for the A21 circuit is provided by circuit A1. This circuit originates in the PDC and is protected by a 20 Amp fuse located in cavity A.

The F12 circuit is spliced and provides voltage to the Powertrain Control Module (PCM) and the Automatic Shutdown (ASD) relay.

The ground for the coil side of the relay is controlled by the PCM through circuit K51. The K51 circuit connects to cavity 51 of the PCM. Logic internal to the PCM determines when the coil side of the relay should be grounded.

When the PCM grounds circuit K51, contacts internal to the fuel pump relay close connecting circuits A1 and A141. Circuit A1 is connected to the BUS bar in the PDC, HOT at all times, and protected by a 20 Amp fuse located in cavity A. Circuit A141 is connected from the relay to the fuel pump motor. Ground for the fuel pump motor is provided on circuit Z1. This ground terminates at the body ground, located on the left rear wheel well.