Replacing Fuel Pump Relay 301: A Step-By-Step Guide

If your car is stalling, refusing to start, or losing power while driving, you may need to replace the fuel pump relay. The fuel pump relay is usually located in the vehicle's long black box with the other relays and fuses, but the location can be different depending on the year, make, and model of your vehicle. It is important to understand the function of the fuel pump relay before attempting to replace it. The fuel pump relay helps your vehicle start by pressurizing the fuel system for the first few seconds before the oil pressure takes over. Without this relay, the engine would not receive fuel while starting.

Check for a faulty fuel pump relay

To check for a faulty fuel pump relay, you can listen out for any unusual noises, such as a lack of the usual humming sound when you turn the ignition key. If you don't hear the relay click or the pump hum, the relay may be faulty. You can also check for oil pressure and ensure that your vehicle is parked on a flat, hard surface with the transmission in park or first gear. Additionally, you can refer to your car's engine compartment fuse box diagram to locate and observe the fuel pump relay. If you notice any issues, consult a certified technician for further diagnosis and repair.

• Turn on the ignition key and listen for the fuel pump to actuate. Pay attention to any buzzing or clicking noises coming from the fuel pump relay.
• Start the engine and check the oil pressure. Some vehicles may only have an oil light indicator, in which case you wait for the indicator light to turn off, indicating that there is oil pressure.
• Park your vehicle on a flat, hard surface and ensure that the transmission is in park (for automatic) or first gear (for manual).
• Place wheel chocks around the front tires, as the rear of the vehicle will be lifted. Engage the parking brake to prevent the rear tires from moving.
• Install a nine-volt battery saver into the cigarette lighter to keep your computer active and vehicle settings current. This step is optional but recommended.
• Open the vehicle's hood and disconnect the battery. Remove the ground cable from the negative post to cut off power to the fuel pump and sending unit.
• Locate the fuse box in the engine compartment and remove its cover. You may need a ratchet to remove hex screws or bolts, or the fuse box may be held on with clips.
• Using the diagram on the fuse box cover or your owner's manual, locate the fuel pump relay.
• Remove the fuel pump relay from the fuse box, paying attention to how it comes out so that you can insert the new one in the same way. You may need a pair of needle-nose pliers for this step.
• Observe the fuel pump relay for any signs of damage or issues. If you notice any problems, consult your owner's manual or a certified technician for further guidance.

If you suspect that your fuel pump relay is faulty, it is important to address the issue promptly to avoid further complications. The fuel pump relay is crucial for pressurizing the fuel system and ensuring the engine receives fuel during startup.

Locate the fuse box

To locate the fuse box, first ensure that the car is turned off and remove the key from the ignition. It's best to locate the fuse in a well-lit location on a flat surface.

Most vehicles have two fuse boxes, with one under the hood and the other in the cabin. You can usually find the cabin fuse box in the dashboard on the driver's side, but some manufacturers also place it below the glove box or in the luggage compartment. If you're still unsure, check your owner's manual or search for it online.

Most Toyota Corolla models, for example, have a fuse box on the driver's side under the dashboard, while the fuse box under the hood is usually on the driver's side near the battery. If you own a 2012-2014 Ford Focus, you’ll find the fuse box in the engine on the driver’s side, while the interior fuse box is located on the passenger’s side, right below the glove box.

If you're trying to troubleshoot an existing electrical problem, the battery must be connected or you may not be able to find the fuse box. Once you’ve located the fuse box, you’ll have to take the cover off to access it. Most manufacturers include a diagram of the fuses on the back of the cover, so you can use it as a guide.

Remove the fuel pump relay

Removing the fuel pump relay

The fuel pump relay is usually located in the vehicle's long black box with the other relays and fuses, although the location can differ in some cars. Most fuel pump relays are located in the engine compartment inside the fuse box.

Step 1: Turn on the ignition key and listen for the fuel pump to actuate. Listen for any buzzing or clicking noise coming from the fuel pump relay.

Step 2: Start the engine and check the oil pressure. Some vehicles will only have an oil light indicator; when the indicator light goes out, there is oil pressure.

Step 3: Park your vehicle on a flat, hard surface. Make sure that the transmission is in park for automatics or in first gear for manuals.

Step 4: Place wheel chocks around the front tires. Engage the parking brake to lock the rear tires from moving.

Step 5: Install a nine-volt battery saver into your cigarette lighter to keep your computer live and your vehicle's settings current.

Step 6: Open the vehicle's hood and disconnect your battery. Take the ground cable off of the battery's negative post to disable the power to the fuel pump and sending unit.

Step 7: Locate the fuse box in the engine compartment and remove the cover. Some fuse boxes are held on with hex screws or bolts and require a ratchet to remove them, while others are held on with clips.

Step 8: Using the diagram on the fuse box cover, locate the fuel pump relay. You can also refer to your owner's manual for the engine compartment fuse box diagram.

Step 9: Remove the fuel pump relay from the fuse box, paying attention to how it comes out as the new one needs to go in the same way. You may need to use a pair of needle-nose pliers to pull it out.

Install a new fuel pump relay

Installing a new fuel pump relay is a relatively straightforward process, but it is important to follow the correct steps to ensure a successful installation. Here is a detailed guide on how to install a new fuel pump relay:

Park Your Vehicle:

Find a flat, hard surface to park your vehicle. Make sure that the transmission is in park for automatic vehicles or in first gear for manual vehicles. This will ensure that your car doesn't move during the installation process.

Engage Parking Brake and Use Wheel Chocks:

Engage the parking brake to lock the rear wheels from moving. Additionally, place wheel chocks around the front tires, as the rear of the vehicle will be lifted.

Disconnect the Battery:

Open the vehicle's hood and disconnect the battery. Remove the ground cable from the battery's negative post to disable the power to the fuel pump and sending unit.

Locate the Fuel Pump Relay:

The fuel pump relay is usually located in the engine's fuse box, which is often a long black box containing various relays and fuses. If you're having trouble locating it, refer to your vehicle's owner's manual for the fuse box diagram.

Remove the Old Fuel Pump Relay:

Pay attention to how the old relay is positioned, as the new one will need to be installed in the same way. You may need a pair of needle-nose pliers to carefully remove it.

Install the New Fuel Pump Relay:

Insert the new fuel pump relay into the fuse box, ensuring it is positioned correctly. Secure it in place, and put the fuse box cover back on, snapping it into place. If you removed any screws or bolts, be sure to reinstall them, being careful not to overtighten them.

Reconnect the Battery:

Reconnect the ground cable to the battery's negative post and tighten the battery clamp to ensure a good connection.

Test the Fuel Pump Relay:

Turn the ignition key on and listen for the fuel pump to activate. You may need to cycle the ignition key on and off a few times to ensure the fuel rail is full before starting the engine. Once the fuel pump stops making noise, turn off the ignition and turn it on again to listen for any buzzing or clicking from the fuel pump relay.

Start the Engine and Test Drive:

Turn the key to start the engine and monitor the cranking period. Remove the wheel chocks and take the vehicle for a test drive. Listen for any unusual noises from the fuel pump or fuel pump relay, and accelerate the engine to ensure the fuel pump is functioning correctly.

Test the vehicle

Once you've replaced the fuel pump relay, it's time to test the vehicle. Here's a step-by-step guide on how to do it:

Step 1: Turn on the ignition and listen for the fuel pump.

Turn the ignition key to the "on" position and listen carefully. You should hear the fuel pump activate and start to operate. Pay attention to any unusual noises, such as buzzing or clicking, coming from the fuel pump relay.

Step 2: Start the engine and check the oil pressure.

Crank the engine and make sure there is sufficient oil pressure. Check for an oil light indicator on your dashboard. If there is one, wait until the indicator light goes out, indicating that there is adequate oil pressure.

Step 3: Drive the vehicle and listen for unusual noises.

Take the car for a drive and pay close attention to any unusual noises coming from the fuel pump or fuel pump relay. Accelerate the engine quickly to ensure that the fuel pump is functioning correctly. A properly working fuel pump should deliver fuel to the engine smoothly, without any hesitation or unusual sounds.

Step 4: Monitor the dashboard for engine warning lights.

Keep a close eye on the dashboard during your test drive. If any warning lights come on, especially the check engine light, it could indicate a problem with the fuel pump or a potential electrical issue within the fuel system. If the check engine light illuminates, further diagnosis or professional assistance may be required.

Step 5: Perform a fuel pressure test (optional but recommended).

For a more comprehensive test, you can perform a fuel pressure test. This will help you determine if there are any issues with the fuel pump or the fuel filter. Here's how to do it:

• Purchase or borrow a fuel pressure gauge from an auto parts store or a machine shop.
• Locate the fuel pump test point, usually near the fuel injectors or the filter injector rail.
• Attach the pressure gauge to the test point or the separation joint/test port.
• Warm up the engine slightly, then rev it while monitoring the pressure gauge.
• Compare the pressure readings at idle speed and at higher engine speeds with the specifications listed in your vehicle's repair manual.
• If the pressure is below specifications or doesn't increase with engine speed, it indicates a problem with the fuel pump and/or filter, and they may need to be replaced.

By following these steps, you can thoroughly test your vehicle after replacing the fuel pump relay. This will help ensure that the new relay is functioning correctly and that there are no other issues with the fuel system.

Frequently asked questions