How to Troubleshoot an Electric Fuel Pump

Sooner or later, the fuel pump in your vehicle will come to fail after a long life of service. The fuel system will experience a drop in fuel pressure, abnormal fuel flow, no fuel flow or fuel leakage somewhere near the gas tank. Most electric fuel pumps are part of a simple circuit that includes a relay, fuse, test connector, indicator gauge and wiring to connect all the components. If you suspect the fuel pump in your vehicle is failing or has failed, follow these simple steps to verify whether you need a replacement. If you have basic knowledge of electricity or want to learn simple, electric circuit troubleshooting procedures, this it the place to start.

Things You'll Need

• Test light
• 2 to 3 inches jumper wire
• Two jumper wires 2 to 3-foot-long

Instructions

1. Go to the back of your car and take off the fuel filler cap. Ask an assistant to turn the ignition on but do not start the engine. Listen closely for a brief, vibratory sound coming from the tank. If you cannot hear the sound, go to the next step.

2. Check the fuel pump circuit fuse. It should be in the fuse panel under the dashboard or in the engine compartment Verify that it is in good condition and the contacts are free from corrosion. If necessary, replace it and test the pump again.

3. Inspect fuel lines, hoses and connectors. Make sure hoses are not torn, bent or obstructed. Verify there are no gas leaks.

4. Locate the fuel pump relay. You might find it in the engine compartment, at the driver or passenger side and close to the windshield or at the front of the engine as part of a cluster of relays. Another common place is under the dashboard.

5. Remove the fuel pump relay. Ask an assistant to turn the ignition on but do not start the engine. Using a test light, check for incoming voltage at the relay connector. If there is no voltage, check for an open or short at the wire between the relay and the fuse panel.

6. Jump the relay connector to apply battery voltage to the fuel pump. After the jumper wire is connected, ask an assistant to turn on the ignition while you listen for fuel pump operation as described in step 1. If the fuel pump works now, replace the relay and test again. Another alternative is to test the fuel pump relay for proper operation.

7. Locate the fuel pump connector at the back of the car and check for incoming voltage with a test light. While you check for voltage, ask an assistant to turn on the ignition but do not start the engine. If there is no voltage, check for an open or short at the wire between the relay and the fuel pump.

8. Check the power and ground connections at the pump and make sure they are good and free of corrosion.

9. Test the fuel pump. Apply direct voltage to the fuel pump. If you cannot easily remove the fuel pump through the trunk of your vehicle, you might want to take a fully charge car battery to the back of the car. Raise the vehicle and secure it firmly on jack stands. Unplug the fuel connector and use a couple of jumper wires to connect the battery to the fuel pump. If the pump does not work, replace it.

Tips & Warnings

• Use the service manual for your particular vehicle if you have difficulty locating components or need to identify wiring designations for testing. You can buy a vehicle service manual at most auto parts stores or consult one for free at most public libraries.

• Some vehicle models provide a special test connector to verify fuel pump operation. Consult your vehicle service manual.

• Even while operating, physical wear may cause a fuel pump to loose pressure. Have it tested by a professional mechanic if you suspect this might be the case.

• Make sure you are in a well ventilated area and away from appliances with open flames like dryers or water heaters whenever you are working with the car’s fuel system.

• Do not allow smoking near your vehicle while working in your car’s fuel system.