Engine Control Module - ECM

A-5 Chart:

Fuel Pump Circuit:

Circuit Description:
When the ignition switch is turned "ON," the Engine Control Module (ECM) will turn "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 shut "OFF" the fuel pump within 2 seconds after ignition "ON" or engine stops, except when a fuel module is used.
The pump will deliver fuel to the TBI unit where the system pressure is controlled to about 62 to 90 kPa (9 to 13 psi). Excess fuel is then returned to the fuel tank.
A fuel module is used on 5.7L (heavy duty) engines to correct a hot restart (vapor lock) during a high ambient condition. It is designed to over-ride the ECM two second pump operation, and will engage the fuel pump for twenty seconds at initial ignition "ON."

Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This procedure applies direct voltage to engage the fuel pump. If the pump does not engage, it may be a fuel pump relay circuit problem which the following step will locate.

2. This step checks voltage from the battery and the ground circuit to the relay.

3. This test determines if there is voltage from the ECM, terminal "A", to terminal "D" on the relay connector.

4. This completes the fuel pump relay circuit; but if this diagnosis was used because the engine would not run, then oil pressure switch should also be diagnosed.

Diagnostic Aids: An inoperative fuel module may be the cause of a hot stall/no start condition. Check for power and ground circuit to and from the fuel module, including the power and grounds circuits at the fuel pump from terminal "A". If OK, and the fuel pump does not run for the specified 20 seconds at initial ignition "ON," replace the fuel module.