Fuel Pump Relay: When To Replace For Optimal Performance

The fuel pump relay is an electromagnetic switch that uses low current to control a higher current circuit. It is a component of the fuel pump circuit, which moves fuel from the fuel tank to the fuel injectors in the engine. When the fuel pump relay goes bad, the fuel pump won't work properly, leading to issues such as ignition problems, the fuel pump running continuously, and a lit check engine light. To test and replace the fuel pump relay, you can refer to online guides and videos, which outline the steps to locate and swap the relay with another similar relay from the power distribution box. The cost of a fuel pump relay is usually less than $20, making it a relatively inexpensive DIY repair.

Testing for a bad fuel pump relay

Step 1: Check for Common Symptoms

Before performing any tests, it is essential to understand the common symptoms of a bad fuel pump relay. These may include:

• Engine cranks but doesn't start: This is often the most common sign of a faulty fuel pump relay. The relay may fail in the open position, preventing voltage from reaching the fuel pump, resulting in the engine being starved of fuel.
• Fuel pump runs continuously: In rare cases, the fuel pump relay can stick in the closed position, causing the fuel pump to run nonstop.
• Illuminated check engine light: The powertrain control module (PCM) may detect a problem with the fuel pump relay and its circuit, turning on the check engine light. However, this may vary depending on the vehicle's make and model.

Step 2: Perform a Preliminary Diagnosis

Before concluding that the fuel pump relay is faulty, it is essential to perform a preliminary diagnosis to rule out other potential issues. This may involve:

• Checking for ignition issues: Ensure that the issue is specifically related to the fuel pump relay and not a more general ignition problem.
• Consulting the owner's manual: Refer to your vehicle's owner's manual to locate the fuel pump relay and its associated fuse. This information will be helpful in the subsequent steps.
• Checking the fuse: Locate the fuse box and identify the fuse associated with the fuel pump relay. Check if the fuse is blown or damaged, as this could be the cause of the issue.

Step 3: Test the Fuel Pump Relay

If the preliminary diagnosis indicates a potential problem with the fuel pump relay, you can perform the following tests:

• Swap the relay: The easiest way to test the fuel pump relay is to temporarily swap it with another relay of the same design from the power distribution box. For example, you can swap it with the air conditioning compressor relay. If the fuel pump runs with the alternate relay, you can conclude that the original fuel pump relay needs replacement.
• Use a multimeter: You can use a multimeter to test the fuel pump relay for continuity. Consult a mechanic or a repair guide to understand the specific procedure for your vehicle.
• Listen for noises: Turn on the ignition key and listen for any buzzing or clicking noises coming from the fuel pump relay. Unusual noises may indicate a problem with the relay.

Step 4: Replace the Fuel Pump Relay if Necessary

If the tests indicate that the fuel pump relay is faulty, you can replace it by following these general steps:

• Park your vehicle on a flat, hard surface and engage the parking brake.
• Disconnect the negative battery terminal to cut off power to the fuel pump.
• Locate the fuel pump relay in the fuse box, usually in the engine compartment.
• Remove the fuel pump relay from the fuse box, paying attention to how it comes out.
• Install a new fuel pump relay in the same way as the old one was removed.
• Reconnect the negative battery terminal.
• Test your vehicle to ensure that the issue has been resolved.

It is important to note that the above steps provide a general guide, and the specific process may vary depending on your vehicle's make and model. Always refer to your owner's manual or consult a professional mechanic for more detailed instructions.

Locating the fuel pump relay

The fuel pump relay is usually controlled by the ignition or the power control module in the vehicle. It is an essential component for the combustion engine to function. When you turn on the ignition, the fuel pump relay is activated and supplies electricity to the fuel pump. When you turn off the ignition, it powers down the fuel pump.

In most vehicles, the fuel pump relay is located inside the fuse box in the engine bay. This is usually a long black box that contains various fuses and relays that enable different parts of your car to function properly. Depending on the year, make, and model of your vehicle, the fuse box might be located under the hood, in the trunk, near the steering column, or on the firewall (the area between the engine and passenger compartments).

• Check the owner's manual: The owner's manual often includes a diagram showing the relay's location. It will also have a section on the fuse and relay box, providing clear guidance on where to start your search.
• Look under the hood: Most relays are found in the fuse box under the hood. The relay box is commonly located inside the vehicle under the dashboard on the driver's side.
• Inspect the fuse box cover: The fuse box cover usually has a diagram indicating each relay's position.
• Listen for the relay: With the key in the "on" position, you may hear a click from the relay.
• Consult online resources: Many car forums and websites offer specific relay locations for different car models.
• Visit a mechanic: If you are unable to locate the relay, a professional mechanic can quickly find and inspect it for you.

It is important to note that the location of the fuel pump relay can vary depending on the vehicle's make and model. If you cannot find it in the engine bay or under the hood, try checking under the dashboard, near the trunk, or on the firewall. Always refer to your vehicle's owner's manual first, as it will provide the most accurate information.

Replacing the fuel pump relay

The fuel pump relay is a crucial component that helps your vehicle start by pressurising the fuel system before the oil pressure takes over. Usually located in the vehicle's long black box with the other relays and fuses, the fuel pump relay may fail when there is no audible humming sound as the ignition is turned, and the car cranks longer than usual before starting.

When to Replace the Fuel Pump Relay

Before replacing the fuel pump relay, it is important to diagnose the issue. Here are some signs that indicate a faulty fuel pump relay:

• No audible humming sound when the ignition is turned on.
• The car takes longer than usual to start.
• There is no fuel pressure during the cranking operation.

Tools Required:

• Needle-nose pliers
• Ratchet with metric and standard sockets
• Wheel chocks
• Nine-volt battery saver (optional)

Step-by-Step Guide to Replacing the Fuel Pump Relay:

Step 1: Prepare the Vehicle

• Turn on the ignition and listen for the fuel pump to actuate. Also, listen for any buzzing or clicking noises from the fuel pump relay.
• Start the engine and check the oil pressure. On some vehicles, there will be an oil light indicator that goes off when there is oil pressure.
• Park your vehicle on a flat, hard surface and ensure it is in park (for automatics) or first gear (for manuals).
• 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.
• Optionally, install a nine-volt battery saver into the cigarette lighter to keep your computer and settings active during the process.

Step 2: Disconnect the Battery

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

Step 3: Locate and Remove the Fuel Pump Relay

• Locate the fuse box in the engine compartment and remove its cover. Some fuse boxes may require a ratchet to remove, while others are held on with clips.
• Using the diagram on the fuse box cover, locate the fuel pump relay. Pay attention to how the relay is positioned.
• Remove the fuel pump relay from the fuse box. You may need to use needle-nose pliers to carefully pull it out.

Step 4: Install the New Fuel Pump Relay

• Install the new relay into the fuse box, ensuring it is positioned correctly as per the previous step.
• Put the fuse box cover back on and snap it into place. Do not over-tighten any screws or bolts, as they may strip.
• Remove and replace the fuel cap from the fuel tank to ensure a proper seal and full pressurisation of the fuel system.

Step 5: Reconnect the Battery and Test

• Reconnect the ground cable to the battery's negative post and tighten the battery clamp.
• Turn the ignition on and listen for the fuel pump to activate. Cycle the ignition key on and off 3 to 4 times to ensure the fuel rail is full before starting the engine.
• Remove the wheel chocks and start the engine, monitoring the cranking period.
• Test drive the vehicle and listen for any unusual noises from the fuel pump or relay. Accelerate the engine to ensure the fuel pump is functioning correctly.
• Check the dashboard for any engine lights that may indicate further issues.

Tips and Tricks:

• If you did not use a nine-volt battery saver, you will need to reset your vehicle's settings, such as radio, electric seats, and mirrors.
• If you used a battery saver, clear any engine codes before starting the vehicle.
• If the engine light comes on after replacing the fuel pump relay, further diagnosis of the fuel pump assembly or electrical issues may be required.

Cost of a fuel pump relay replacement

The cost of replacing a fuel pump relay varies depending on the car model, the location, and the labour involved. On average, the cost of replacing a fuel pump relay is estimated to be between $71 and $79, with labour costs making up $30 to $38 of that amount, and parts typically priced at around $41. However, prices can vary, for example, a fuel pump relay replacement for a Chrysler Crossfire was priced at AUD $549.95 (approximately US $434).

It is also worth noting that some people have reported being quoted higher prices for this service, with one person being quoted $260 for the replacement of a fuel pump relay and fuel injectors, and another being quoted $512 for a similar repair on a Ford pickup.

In terms of where to get the replacement done, it is generally recommended to seek out a trusted mechanic or a specialist who can provide a competitive price. Dealerships tend to charge more, and there may be local mechanics or specialists who can offer a more competitive rate.

Additionally, it is important to note that relays are generally inexpensive, sealed units that should be replaced rather than repaired. Attempting to repair a relay could lead to further issues, such as humidity entering the relay or even melting of the unit.

Symptoms of a bad fuel pump relay

A faulty fuel pump relay can cause a range of issues with your car's performance. Here are some of the most common symptoms of a failing fuel pump relay:

• Ignition issues: One of the most common signs of a bad fuel pump relay is when the engine cranks but doesn't start. This happens because a faulty fuel pump relay fails in the open position, preventing voltage from reaching the fuel pump. As a result, the engine doesn't get the fuel it needs to run.
• Fuel pump running continuously: In some cases, the fuel pump relay can get stuck in the closed position, causing the fuel pump to run continuously, even when the key is out of the ignition.
• Illuminated check engine light: In some vehicles, the engine computer or powertrain control module (PCM) monitors the fuel pump relay. If it detects a problem, it turns on the check engine light and stores a diagnostic trouble code (DTC). However, not all vehicles will illuminate the check engine light for a bad fuel pump relay.
• Intermittent starting issues: You may experience multiple attempts to start your car, especially when the vehicle is cold. Over time, this problem can worsen until the vehicle won't start at all.
• Unexplained battery drainage: A fuel pump relay that is stuck closed can cause the fuel pump to run continuously, draining your battery. You may be able to hear the fuel pump running from the rear of the vehicle even after it's turned off.
• Jump-starting or remote-starting resolves starting issues: Fuel pump relays perform better at higher voltages. Jump-starting or remote-starting your vehicle can provide the higher voltage needed to start the car, temporarily resolving the issue.
• Seasonal starting issues: You may find that your vehicle starts fine during the warmer months but struggles to start during colder months.
• Stalling after starting or while driving: Your vehicle may start but then stall after a few seconds or minutes. This could be related to the fuel pump relay or a thermal expansion issue inside the TIPM or other electrical components.

It's important to note that these symptoms can also be caused by other issues, so it's recommended to perform a thorough diagnosis of your vehicle before replacing any parts.

Frequently asked questions