Chart A-7A, Fuel System Diagnosis: Notes

When the ignition switch is turned ON, the ECM and the control relay will turn ON the in-tank fuel pump under the following conditions:

• During engine cranking.
• Ignition ON, engine running (ECM receiving ignition input).
• Coolant temperature less than 10°F (12°C), ignition ON, for three seconds.

Fuel pump will remain ON as long as the engine is cranking or running, and the ECM is receiving HEI distributor reference pulses.

If there is no reference pulse, the ECM will shut off the fuel pump within 3 seconds after key ON. Excess fuel is then returned to the fuel tank.

1. This step verifies that the fuel pump operates when engine is cranking. Use a helper for this step.
2. This step checks circuits 440, 120, 150 and the fuel pump.
3. This step checks control relay.
4. This step checks circuit 465 and ECM ground.