How to Diagnose a Fuel Pump Relay

fuel pump relay is an integral part of an automobile’s engine assembly and is responsible for switching as well as controlling the fuel pump at the time of ignition and shut down. The location of the fuel pump relay varies from one car model to the other but the purpose of the device remains the same. It is a durable piece of machinery which, however, with time, may wear or short out.

Understanding the symptoms of a faulty fuel pump relay can simplify your life and correct the problem(s) beforehand, so as to avoid any possible inconvenience or problems thereafter. Hence, using the steps mentioned below you can go about diagnosing the possible problems with your fuel pump relay correctly which can enable you to take an effective control and corrective action.

Tools and Materials Needed:

  • New Fuel Pump (if needed)


Step 1: Understand and Acknowledge the Symptoms

There are several problems that your car might face if the fuel relay has gone out of order.

  • The engine may not start but just produce grinding noises like it is about to start
  • The car may lose power or simply slow down while being driven
  • The car may come to a standstill without the driver wanting to and the engine may take quite a while to start up again once the car halts
  • The absence of a startup noise of the fuel pump relay

Step 2: Run a Check Up

In order to be sure that there is a problem with your car’s fuel pump relay, run a little check up. Put your car keys into the ignition switch and turn it to the ‘II’ position. However, care must be taken so as to not crank the car at this stage.

Step 3: Listen for the Sound

Once you switch the ignition on, the fuel pump should get started. You should listen for a slight humming or buzzing sound that lasts for a couple of seconds. Therefore, you would have to listen closely as this sound will help you analyze the state of your fuel pump relay.

Step 4: Check the Fuse

If you do not hear the fuel pump energizing, it suggests that the problem might be with the fuse responsible for providing power to the relay. It is situated in the fuse panel under the dashboard of your car and therefore, if this is the case, open the fuse panel and run a check on the fuse. If you find the fuse blown, do replace it with a new one and run Step 2 and 3 again.

Step 5: Replace or Fix the Relay

The above step should hopefully sort the problem out and you should not face any problems with your car. If, however, by the time of completing Step 4, you are still not able to hear the sound of the fuel pump energizing, get the fuel pump relay tested by a professional mechanic or simply replace it with a new one.