How to Test Fuel Pump Relay

Owning a car is a tremendous responsibility but when your gas mileage becomes an issue you can lose a lot of money to have someone else test fuel pump activity. There are plenty of things that you can do yourself to maintain the life of your vehicle and this one of those things. Testing the relay of a fuel pump is relatively simple as they do not have many parts. The most common parts to burn out or break include the contact and the coil. When either of these begin to fail the current to the electrical circuit will be also fail and that in turn means your fuel pump will cease to function properly. The following article will show you how to troubleshoot your fuel pump.

Step 1 - Locate the Fuel Pump Relay

Make sure that you have enough light and room to work. The most important thing about this project is the fuel pump. Open your vehicle's hood and find the fuse panel. The majority of vehicles made today have the fuel pump relay near here. If it is not located here then you may have to explore the engine compartment more thoroughly. Under the dashboard is the next likely location to find the relay. The fuel pump relay can be found on either side of the car be it the passenger side or the driver's side. The fuse box will be clearly marked on the back of it or on the inside and these will identify the fuel pump relay.

Step 2 - Accessing the Fuel Pump Relay

Unplug the fuel pump relay but, when you do, be wary that you do not break the cover and connecting tabs. Inside the fuel pump relay you will need two control circuit terminals and two power circuit terminals. The diagram for the fuel pump relay will be printed on the cover for easy reference. If the vehicle is old then the diagram could have faded or been removed previously. If this is your situation then locate two thin wires. They feed the control circuit while the thick wires are the power terminals.

Step 3 - Test Fuel Pump Relay

The ohmmeter has to be on the lowest setting. Touch the leads to each power relay terminal. If the reading is not infinite resistance then replace the relay. Connect the fused jumper to the battery's positive and to a control terminal. Attach the regular jumper cable to the other terminal and to the ground of the vehicle. The fuel pump relay should click. If not then switch the points of the jumper cables. If the relay still does not click then replace the relay. Now, test the power terminals. Maintain the positions of the jumper cables. The power terminals of the fuel pump relay should not read infinite resistance and, if they do, the relay needs to be replaced. The correct reading should be, at the least, in the hundredths but optimally it should be in the thousandths.