Your car’s fuel pump relay is an electronic part that acts as a switch to turn the pump itself on or off as needed. If your engine has any problems with the start-up process, including stalling or not starting at all, these could be signs of a bad relay.

Our guide will teach you how to tell if fuel pump relay is bad and give you some possible solutions to the problem.

how to tell if fuel pump relay is bad

1. Your Engine Will Not Start

You can usually find your car’s fuel pump relay mounted on a fuse box in the engine bay. Because it functions like a switch that controls the pump itself, the relay is also what brings power to the pump. The first method for how to tell if fuel pump relay is bad is seeing whether your car will start. Without a working relay, the pump cannot inject the necessary fuel to complete the ignition process.

Note that you may still hear the engine making noise when you try to start your vehicle even if the relay does not work. Other parts of your car’s engine might be in working order, but they won’t have fuel.

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2. The Engine Starts and Stalls

The next step in our guide for how to tell if a fuel pump relay is bad involves an engine that can start but won’t stay active. Even if your relay is working, it may not function continuously. If this is the case, the pump relay can probably start your car, but it will fail to supply the power your vehicle needs to keep going. A bad fuel pump relay will cut the power to your car and stall the engine while you are driving.

Keep in mind that a bad fuel pump relay might be faulty or in total failure. In either example, the engine might stall. A relay that is faulty might allow you to restart your engine after you give it a break. However, a failed relay will be unable to do anything for your car.

3. You Cannot Hear Noise from the Pump

If you turn your car on but the fuel pump isn’t making its customary noise, it might be a third sign telling you that the fuel pump relay is bad. There are two ways you can listen for the relay to tell if it is faulty or failing.

Inside the Car

Sit inside your car in an area with relatively little background noise. Once inside, listen closely to see if you can hear a humming or whining sound. This noise will typically be at a very low volume, so it may take some time and patience to hear it. Take a few moments to listen for this noise in silence. If you do not hear it even after waiting for some time, this may be one sign that your fuel pump relay is bad.

Outside the Car

If you want to be certain your fuel pump relay is bad, you can try to listen for those same noises from outside your car. With your car ignition on, move over to the fuel tank area of the vehicle. Crouch next to the fuel tank and listen for a hum or whine. If you cannot hear any noise, you may have a problem with your fuel relay.

4. How to Tell if Fuel Pump Relay Is Bad While Driving

Your car’s fuel pump relay may be able to supply enough power to the vehicle to allow you to drive it. However, if the relay is faulty, you may notice some problems with the car’s performance. If your car starts to slow down while you are driving, it may be a sign of a bad fuel relay. The device is able to supply your car with enough power to function, but not enough for peak performance. Your car is low on energy, so it may slow down while you are on the road. If this happens, it is best to find a way to pull over and diagnose the problem as soon as possible. There is a chance that a bad fuel pump relay could stall your car on a busy road.

Replacing a Bad Fuel Pump Relay

Knowing how to tell if fuel pump relay is bad is only half the battle. You may wish to remove the faulty device so that you can install a new one. Once you have the fuel pump relay of your choice, you can use the steps in the next part of our guide to remove the old unit.

Secure the Vehicle

Make sure that you park your car on a flat, even surface and engage the parking brake for added safety.

Install a battery

You may wish to insert a battery into your car’s cigarette lighter port to keep the computer active while you change the fuel pump relay.

Find the Fuse Box

Disconnect your car’s battery and find the fuse box. You’ll need to take the cover off the box. Your fuse box may use either screws, bolts, or clips to secure itself. Use the appropriate tools to open your fuse box.

Locate the Relay

Your fuse box cover might have a diagram on the inside that details the location of its components. Use this map to find your bad fuel pump relay and remove it. Check the position of the faulty relay as you are removing it. The new relay needs to go into the fuse box in the same way the old one did.

Wrapping Up

Learning how to tell if fuel pump relay is bad and replacing it when needed is an important part of vehicle maintenance. This relay is a small yet integral part of your engine. If it fails, it could prevent your car from starting, negatively impact its performance, or perhaps lead to disastrous results on the road.

Please feel free to comment and share your tips on the signs of a bad fuel pump relay.

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