Chart A-5 Fuel Pump and Relay Electrical Test

Chart A-5:

Fuel Pump Control Wiring:

CIRCUIT DESCRIPTION
When the ignition switch is turned "ON", the PCM will energize the fuel pump relay which turns "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the PCM is receiving distributor reference pulses. If there are no reference pulses, the PCM will de-energize the fuel pump relay which will shut "OFF" the fuel pump within 2 seconds after ignition "ON" or engine stops.

The fuel pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator where the system pressure is controlled. Excess fuel pressure is bypassed back to the fuel tank. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal located in the engine compartment using a fused jumper.

Improper fuel system pressure may contribute to one or all of the following symptoms:
^ Cranks but won't run
^ Code 44 or 45
^ Cuts out, may feel like ignition problem
^ Hesitation, loss of power or poor fuel economy


TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. This test checks the fuel pump relay power CKT 480 and ground CKT 450.

2. This step determines if the fuel pump circuit is being controlled by the PCM. The PCM should energize the fuel pump relay and turn the fuel pump "ON". If the engine is not cranking or running, the PCM should de-energize the relay and/or fuel pump within 2 seconds after the ignition is turned "ON".

3. This test checks for an open or short to ground in CKT 465.