Rajan Wilcox
A fuel injector relay is an electromagnetic switch that uses low current to control a higher current circuit. A faulty fuel injector relay can cause a range of issues, including ignition problems, an illuminated check engine light, and a vehicle that suddenly loses power or stalls while driving. To check for a faulty fuel injector relay, you can look for common symptoms, such as corrosion on the relay prongs, no noise coming from the fuel pump, or an engine that refuses to start. You can also perform a swap test by replacing the fuel injector relay with another relay of the same design and observing if the issue persists. If you are uncomfortable performing the checks yourself, it is recommended to consult a mechanic.
| Characteristics | Values |
|---|---|
| Symptoms of a faulty fuel pump relay | Vehicle stalls while driving, loses power while driving, issues with ignition, fuel pump running continuously, illuminated check engine light, vehicle won't start, engine cranks but doesn't fire |
| Location of fuel pump relay | In the fuse box in the engine bay, under the hood, on the firewall, or near the steering column |
| Testing the fuel pump relay | Check for corrosion and overheating, inspect terminals and sockets, perform a multimeter test, temporarily swap with another relay |
| Maintenance | Clean engine and components regularly, bring the vehicle to a mechanic for maintenance |
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What You'll Learn
Check for common symptoms of a faulty fuel pump relay
A faulty fuel pump relay will leave you without a working fuel pump, and your car will begin to exhibit some noticeable symptoms. Here are some common symptoms of a failing fuel pump relay to watch out for:
Engine Won't Start
The most common sign of a bad fuel pump relay is an engine that cranks but doesn’t start. A faulty fuel pump relay will leave you without a working fuel pump, and the engine will be starved of fuel and refuse to run. If your car won't start or keeps cutting out, it could be due to a faulty fuel pump relay.
Engine Stalling
A faulty fuel pump relay can cause the engine to stall while driving, and you may coast to a stop. Engine stalling can be dangerous, so it’s important to have the problem assessed right away. If your car restarts after a short while, your fuel pump relay is faulty and requires immediate inspection.
No Noise from the Fuel Pump
When you turn on the ignition, the fuel pump should make a whirring sound. If you are unable to hear this, the fuel pump relay may be malfunctioning.
Loss of Two Functions at a Time
If you experience the loss of two functions simultaneously, there is a good chance the double relay has failed. Symptoms include windshield wipers not working, the horn not functioning, door locks failing to lock/unlock, and backup lights working intermittently.
Check Engine Light Illuminated
A malfunctioning fuel pump relay can trigger the Check Engine Light to illuminate on the dashboard due to a disruption in the fuel delivery system. However, this may not be supported by all makes and models of vehicles.
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Locate the fuel pump relay in your vehicle
The fuel pump relay is a crucial component in the ignition process of your vehicle. It provides electrical power to the fuel pump when the engine is started, acting as a gateway between the electrical and fuel delivery systems. Without a functioning relay, your vehicle cannot deliver fuel to the engine, so it's important to be able to locate it.
The location of the fuel pump relay can vary depending on the vehicle's make and model. In some cars, it is found under the hood in the fuse box, typically a long black box with various fuses and relays. The fuse box may be held on with hex screws or bolts and require a ratchet to remove it, or it may be held on with clips. Once you have removed the cover, you can use the diagram on the fuse box cover to locate the fuel pump relay.
If you are unable to locate the fuel pump relay in the engine compartment, it may be located elsewhere in the vehicle. Some other possible locations include under the dashboard, near the trunk, or inside the glovebox.
Online resources and forums can be a helpful way to determine the location of the fuel pump relay in your specific vehicle. Additionally, always refer to your vehicle's owner's manual, as this should provide specific instructions on locating and accessing the fuel pump relay.
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Inspect the relay for signs of corrosion or overheating
To check for signs of corrosion or overheating on a fuel injector relay, you must first locate the relay. The fuel pump relay is usually located in the engine bay, inside a black fuse box. It is cube-shaped and connects with prongs like an electrical plug.
Once you have located the relay, carefully pry it out with a flathead screwdriver. Disconnect the plug-in and fuse to the relay to remove it. Now, you can begin inspecting the relay for signs of corrosion and overheating.
Inspect the terminals and sockets for any signs of corrosion. Corrosion will prevent the proper flow of current. If you notice any corrosion, clean the terminals and sockets with an electrical contact cleaner. Remember to wear gloves and goggles for protection.
Overheating can also prevent the proper flow of current and indicate problems with the relay or the circuits it connects to. If you suspect the relay is overheating, check the contact and the coil, as these are the most common parts to burn out or break. Additionally, heat expansion can worsen internal electrical faults in the relay, leading to failures when the engine bay temperature rises. This could be why some cars start fine when cold but struggle when hot.
Regular maintenance and cleaning of the relay are important to ensure optimal performance and prevent potential problems.
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Test the relay with a multimeter
To test a fuel pump relay with a multimeter, you will need to locate the fuel pump relay in your vehicle. The fuel pump relay is usually located in the fuse box under the hood or in the passenger compartment. Turn off your vehicle and remove the key from the ignition before you begin.
Once located, remove the fuel pump relay from your vehicle and clean and inspect it. Hold the relay upside down so the prongs point up and firmly scrape them with a wire brush to remove any rust or corrosion.
Now, take your multimeter and set it to measure resistance (ohms). Attach the multimeter to a ground and put the voltage on for 12V, then go back to resistance. You should see a reading of less than 5 ohms.
Next, attach a jumper wire to the positive terminal on your vehicle's battery. Connect the other end of the jumper wire to the positive relay terminal. Then, touch one probe of the multimeter to the jumper wire and the other probe to one of the coil pins of the relay. Repeat this process with the other coil pin. You should get a reading between 50 and 120 ohms. If the reading is too high, too low, or infinite, the relay coil is defective and needs to be replaced.
To test the relay switch, set the multimeter to measure voltage (volts). Touch one probe of the multimeter to the jumper wire and the other probe to the pin that connects to the fuel pump. You should get a reading of zero volts. Now, connect the jumper wire to one of the coil pins of the relay and touch the other coil pin with the multimeter probe. You should hear a click sound and get a reading of 12 volts. If you do not hear a click or get a different voltage reading, the relay switch is defective and needs to be replaced.
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Replace the relay if necessary
If you've determined that your fuel injector relay is faulty and needs to be replaced, the process is relatively straightforward and can be done yourself. The fuel pump relay is usually located in the vehicle's long black box with the other relays and fuses, but the location can vary depending on the car. You can find it in the engine bay, under the hood, on the firewall, or near the steering column. Once you've located the relay, carefully pry it out with a flathead screwdriver.
Before installing a new relay, it's important to address any underlying issues that may have caused the previous relay to fail. Check for corrosion, overheating, or other signs of damage. Clean any corroded terminals and sockets with electrical contact cleaner, and ensure that the voltage is stable. Replace any blown fuses and worn-out relays. You should also clean the engine and its components to prevent dirt buildup.
When you're ready to install the new relay, make sure it is compatible with your vehicle's make and model. The new relay should cost less than $20, but the exact cost will depend on the specifics of your vehicle. Insert the new relay into the black box, ensuring that it is securely connected. Reconnect the plug-in and fuse, and close the box.
After replacing the relay, it's important to test the fuel pump to ensure it's functioning correctly. Start the vehicle and listen for any unusual noises from the fuel pump or relay. Accelerate the engine to make sure the fuel pump is working properly. Monitor the dashboard for any engine lights, as this may indicate further issues with the fuel pump assembly or electrical problems within the fuel system. If problems persist, consult a certified technician for further diagnosis and repair.
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Frequently asked questions
There are several symptoms of a faulty fuel injector relay, including ignition issues, the fuel pump running continuously, and an illuminated check engine light. Your engine may also stall while driving and coast to a stop.
The fuel injector relay can often be found in the fuse box in the engine bay, which is usually a long black box containing various fuses and relays. If you cannot find it, check your owner’s manual.
First, remove the relay from the fuse box by pulling it straight out. Then, clean the relay prongs with a wire brush and check for any signs of rust or corrosion. If the relay is faulty or has a loose connection, it may be necessary to replace it.
Set the multimeter to the lowest range on the Ohms scale or set it to 'continuity'. Connect one lead to the power circuit pin and the other lead to the power terminal. If the reading is greater than 0, then the circuit inside the relay is faulty.
If your fuel injector relay is faulty, you can try to replace it with a new one. If you don’t feel comfortable doing this yourself, you can hire a mechanic to look at your vehicle.
