Replacing In-Tank Fuel Pumps: A Step-By-Step Guide

Replacing an in-tank fuel pump is a complex process that requires careful attention to safety precautions. Before starting, ensure you have the necessary tools and a well-ventilated workspace, free from sparks, flames, and cigarettes. It is also crucial to disconnect the negative battery cable and drain the fuel tank to avoid injury and spillage. When removing the fuel pump, follow the vehicle's specific instructions, which may involve dropping the fuel tank or accessing it through an access door. Finally, when installing the new fuel pump, pay attention to the fuel line connections, electrical connectors, and proper sealing to avoid leaks.

Safety precautions

Replacing an in-tank fuel pump can be a dangerous task if the proper safety precautions are not taken. Here are some detailed safety measures to follow when undertaking this procedure:

Work in a Well-Ventilated Area: Ensure that the workspace is adequately ventilated to prevent the buildup of fuel vapors, which can be highly flammable. Open flames or sparks from electrical equipment, cigarettes, or any other source can easily ignite the vapors, leading to an explosion or fire.

Wear Appropriate Protective Gear: Put on safety goggles and gloves before starting the replacement process. This will protect your eyes from any fuel splashes and your hands from harmful chemicals present in the fuel.

Use Approved Containers for Fuel: Obtain containers that are specifically approved for storing fuel. When removing the fuel tank, carefully drain the remaining fuel into these containers to avoid spills and reduce the risk of fire.

Relieve Fuel Pressure: Before opening the fuel system, always relieve the fuel pressure. Opening a pressurized fuel system can be extremely dangerous, as the escaping fuel under pressure can easily catch fire or cause injury.

Disconnect the Battery: Disconnect the negative (-) terminal of the battery to prevent any accidental electrical sparks. This is crucial as you will be working around gasoline, and a spark could ignite the fuel, leading to a hazardous situation.

Clean Up Spills Immediately: Keep rags or other absorbent materials on hand to wipe up any fuel spills immediately. Gasoline is highly flammable, and even a small amount of spilled fuel can pose a significant safety hazard.

Keep a Fire Extinguisher Nearby: Have a fire extinguisher specifically rated for gasoline fires ready and easily accessible. This will enable you to quickly respond to any fire that may occur during the replacement process.

Avoid Smoking: Do not smoke while working on the fuel pump replacement. Smoking near gasoline vapors or spills can easily lead to a fire or explosion.

Use a Support Jack: When lifting the vehicle to access the fuel tank, ensure that you use a support jack to securely hold the vehicle in the lifted position. This will prevent the vehicle from accidentally falling or shifting during the replacement process.

Handle Level Sender with Care: The level sender has delicate circuitry. Be cautious when handling it to avoid any damage that could affect its functionality.

Avoid Bench-Testing the New Fuel Pump: In-tank fuel pumps are designed to operate while submerged in gasoline for lubrication and cooling. Bench-testing a new fuel pump may damage it, so it is recommended to avoid this step.

Cover the Fuel Tank Opening: When the fuel pump assembly is removed, cover the fuel tank opening to prevent dust, dirt, or other foreign matter from falling into the tank. This will help ensure that no contaminants enter the fuel system.

Reinstall the Fuel Filter: After replacing the fuel pump, remember to also replace the fuel filter. This will ensure that your new pump runs smoothly and prevent any issues caused by a clogged or dirty filter.

Removing the fuel pump

Before you begin, ensure you have all the necessary tools and safety equipment. You will be working with gasoline, which is highly flammable, so it is important to take the proper precautions. Work in a well-ventilated area, preferably outdoors, and keep all sources of sparks or flames away from the vehicle and fuel tank. Make sure you have a fire extinguisher nearby, and wear safety goggles, gloves, and appropriate clothing to protect yourself from fuel spills and splashes.

First, disconnect the negative battery cable. Then, relieve the fuel system pressure. This can be done by running the engine and pulling the fuel pump relay, or by pressing the Schrader valve on the pressure line momentarily to release a small spray of fuel.

Next, locate the fuel tank and remove it from the vehicle. This process will vary depending on the vehicle, but you will likely need to use a jack to support the tank and lower it. Some vehicles may have an access port under the rear seat or in the trunk area, which can save time and effort.

Before removing the old pump, take note of the fuel line connections and wiring. Be sure to also check your tank for any leaks or damage, and if your tank has a drain cock or drain plug, use it to remove the fuel inside the tank. If not, use a hand siphon pump to drain the tank. Do not use an electric pump as this may cause sparks.

Once the tank is empty, carefully disconnect the wiring connections, fuel lines, and vent hoses on the top of the tank. Then, remove the bolts from the straps holding the fuel tank in the vehicle, and fully lower the tank.

Now, you can remove the old fuel pump. Clean the top of the tank first to prevent any dirt or debris from falling into the tank during removal. Refer to your service manual for instructions on removing the fuel pump assembly. Typically, there will be a plate held in place with screws or bolts, which can be released to enable the removal of the pump.

Finally, inspect the old pump and the fuel tank for any signs of damage or wear. If the fuel tank is dirty, it should be cleaned or replaced. Similarly, if the filter screen on the pump inlet is clogged, it will need to be replaced.

Installing the new fuel pump

Once you have the fuel pump assembly out of the fuel tank, place it on a workbench or suitable workspace so you can install the new pump. Examine the electrical wiring, hoses, and overall condition of the assembly. If necessary, replace the assembly; otherwise, it may affect the operation of your new pump, and you'll need to redo the job in the near future.

Detach the fuel pump by disconnecting the bottom bracket, fuel pump strainer, electrical wires, and fuel outlet hose from the pump.

Before installing the new fuel pump, use a flashlight to inspect the fuel inside the tank and check for excessive contaminants. It's normal to have some dirt and foreign objects, but excess particles or bad/rotten fuel will cause the new pump to fail.

Match the old pump to the new unit. Sometimes they can look a little different, as updates are rolled out. Install the gas level float arm and a new primary fuel filter (strainer on the pump).

Clean mounting and seal surfaces using a shop towel and carburetor cleaner. This will ensure a proper seal.

Install the new O-ring gasket/seal before installing the new pump assembly.

Gently lower the replacement pump into the fuel tank, taking note of the fuel level sender orientation, and reinstall the mounting ring or bolts. It makes a difference in the quality of the fuel pump, and there are many to choose from. We recommend OEM (factory) pumps.

Complete the job by reinstalling the tank and reversing the order of the steps above. Add fuel before turning the key so the pump does not start dry. If the car has a secondary fuel filter, it should be changed as well. To help the pump last, it's a good idea to replace the fuel pump control relay.

Now, reconnect the negative cable to the battery. Start the vehicle and check for leaks.

If you have not changed the fuel filter in more than a year, this is a good time to install a new one. That way, your new pump will have a clear path to fuel the engine. Refill the tank with enough gasoline to cover the fuel pump—usually a quarter of a tank full.

Testing the installation

Now that you've replaced the in-tank fuel pump, it's time to test the installation to ensure everything is functioning correctly. Here are the steps you should follow:

• Reconnect the negative terminal of the battery: This is important as it provides power to the fuel pump and other electrical components in your vehicle.
• Check the pump motor function: Turn on the ignition switch. Listen carefully for a humming sound coming from the pump motor. The Engine Control Unit (ECU) energizes the pump motor to pressurize the fuel line when you first turn on the ignition. Subsequently, you may not hear the sound again as the fuel line may still have enough pressure.
• Start the engine: If the pump motor is functioning, try to start the engine. If it doesn't start or runs roughly, proceed to the next step of connecting a pressure gauge. If the engine starts and runs smoothly, you can skip to the final step.
• Connect a pressure gauge: If the engine doesn't start or run smoothly, connect a pressure gauge to the fuel feed spout. Turn on the ignition switch and listen for the humming sound from the fuel pump. The pressure gauge should read around 49 psi. If the pressure is low or non-existent, there may be a leak in the fuel pump assembly. Check the O-rings on the pressure regulator, pump nozzle, and feed spout for any signs of leakage.
• Reinstall remaining parts: If the pressure is within the normal range, proceed to reinstall any remaining parts that have not yet been installed.
• Final checks: Return the service cover and install the seat cushion. Congratulations! You've successfully replaced and tested your in-tank fuel pump. If, however, the replacement hasn't solved your initial problem, it may be due to incorrect initial troubleshooting. You may need to troubleshoot further to identify and resolve the issue.

It is important to note that these steps are based on the assumption that the fuel pump and/or filter were previously determined to be defective. Therefore, this testing procedure focuses solely on verifying the integrity of the installation.

Completing the replacement

Now that you have the fuel pump assembly out of the fuel tank, you can install the new pump. Place the assembly on a workbench or a suitable workspace to install the new pump, unless you are replacing the whole unit.

Examine the electrical wiring, hoses, and overall condition of the assembly. If necessary, replace the assembly, or else it may affect the operation of your new pump.

Detach the fuel pump by disconnecting the bottom bracket, fuel pump strainer, electrical wires, and fuel outlet hose from the pump.

Install the new fuel pump in the assembly, and reconnect the wires, hoses, new pump strainer, and bracket.

Clean the inside of the tank with pressurized water to remove dirt and let it dry before reinstalling the new fuel pump assembly.

Clean the fuel tank opening with carburetor cleaner before positioning the O-ring or rubber seal.

Install the assembly with the new fuel pump in the tank, along with a bracket-assembly seal gasket. You may want to apply a thin layer of petroleum jelly to the bottom of the rubber seal to hold it in place as you lock the sending unit onto the tank.

With the pump module in place, lock the cam ring by rotating the ring clockwise using a brass chisel or screwdriver and hammer (or bolt the unit in place).

Then, use the floor jack to lift the fuel tank just enough to reconnect the fuel lines, pump sending unit electrical connector, and filler neck to the tank.

Carefully lift the fuel tank into position, making sure not to squeeze or damage the fuel lines and electrical connectors.

Secure the tank by attaching the tank straps or flange mounting bolts.

With the fuel tank in place and all hoses and electrical connectors plugged in, lower the vehicle if you had to raise it. Or reinstall the access door.

Connect the negative cable to the battery.

Start the vehicle and check for leaks.

If you have not changed the fuel filter in more than a year, now is a good time to install a new one. That way, your new pump will have a clear path to fuel the engine.

Refill the tank with enough gasoline to cover the fuel pump—usually a quarter of a tank full.

Congratulations! You've just completed a nice replacement job.

Frequently asked questions