Chart A5 - Fuel System Electrical Test: Notes

When the engine is stopped, the pump can be turned on by applying battery voltage to the test terminal. The fuel pump test terminal is located in the engine compartment. Improper fuel system pressure may contribute to a cranks, but won't run condition, Code 44 or 45, engine cut-out (may feel like ignition problems), hesitation, loss of power and poor fuel economy.

1. If the fuse is blown, a short to ground in circuits No. 120 or 839, or the fuel pump itself is the cause.
2. Determines if the fuel pump circuit is being controlled by the ECM. The ECM should energize the fuel pump relay. Since engine is not cranking or running, ECM should de-energize the relay within 2 seconds after ignition is turned on.
3. Turns on the fuel pump if circuit No. 120 wiring is okay. If the pump runs, it is a basic fuel delivery problem.
4. This test will determine if a short to ground on circuit No. 120 caused the fuse to blow. To prevent a misdiagnosis, be sure the fuel pump is disconnected before the test.
5. Checks for a short to ground in the fuel pump relay harness circuit No. 839.
6. Checks for open in fuel pump circuits No. 120 or 150 or the pump.
7. Determines if the ECM is in control of the fuel pump relay through circuit No. 465.
8. The fuel pump control circuit includes an engine oil pressure switch with a separate set of normally open contacts. The switch closes at about 4 psi (.28 kg/cm² ) of oil pressure and provides a second battery feed path to the fuel pump. If the relay fails, the pump will continue to run using the current supplied by the closed oil pressure switch. This test checks the oil pressure switch to ensure it provides power to the fuel pump should the pump relay fail.

When the engine is stopped, the pump can be turned on by applying battery voltage to the test terminal. The fuel pump test terminal is located in right front corner of engine compartment. Improper fuel system pressure may contribute to a "engine cranks, but won't run" condition, Code 44 or 45, engine cut-out (may feel like ignition problems), hesitation, loss of power and poor fuel economy.

1. If the fuse is blown, a short to ground in circuits No. 120 or 839, or the fuel pump itself is the cause.
2. Determines if the fuel pump circuit is being controlled by the ECM. The ECM should energize the fuel pump relay. Since engine is not cranking or running, ECM should de-energize the relay within 2 seconds after ignition is turned on.
3. Turns on the fuel pump if circuit No. 120 wiring is okay. If the pump runs, it is a basic fuel delivery problem.
4. This test will determine if a short to ground on circuit No. 120 caused the fuse to blow. To prevent a misdiagnosis, be sure the fuel pump is disconnected before the test.
5. Checks for a short to ground in the fuel pump relay harness circuit No. 839.
6. Checks for open in fuel pump relay ground circuit No. 450.
7. Determines if the ECM is in control of the fuel pump relay through circuit No. 465.
8. The fuel pump control circuit includes an engine oil pressure switch with a separate set of normally open contacts. The switch closes at about 4 psi (.28 kg/cm² ) of oil pressure and provides a second battery feed path to the fuel pump. If the relay fails, the pump will continue to run using the current supplied by the closed oil pressure switch. This test checks the oil pressure switch to ensure it provides power to the fuel pump should the pump relay fail.