Chart A-5 Fuel System Electrical Test

Chart A-5:

Fuel Pump Circuit:

CIRCUIT DESCRIPTION:
When the ignition switch is turned "ON," the ECM 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 ECM is receiving distributor reference pulses. If there are no reference pulses, the ECM will de-energize the fuel pump relay which will shut "OFF" the fuel pump within 2 seconds after ignition key is turned "ON" or the 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.

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. Check for B+ and ground at the fuel pump relay.

2. Checks that ECM is supplying voltage to fuel pump relay.

3. This checks the fuel pump circuit to the tank for opens or shorts.