Replacing Intank Fuel Pumps: A Step-By-Step Guide

Replacing an in-tank fuel pump can be a challenging task, but with the right tools and safety precautions, it can be accomplished at home. Before beginning, it is important to determine the condition of the fuel pump and identify the specific reason for replacement. Some common issues include a shorted or burned pump motor, a weak pump that fails to provide adequate fuel pressure, or a clogged or dirty filter resulting in low fuel pressure. It is crucial to work in a well-ventilated area, away from open flames and sparks, and to have a fire extinguisher readily available when working with gasoline. Additionally, it is recommended to drain the fuel tank as much as possible to reduce the risk of injury when handling the tank. The level of difficulty for this task may vary depending on your skillset, experience, and the specific vehicle model.

Safety precautions

When replacing an in-tank fuel pump, safety should be the top priority. Here are some detailed safety precautions to follow:

Work in a Well-Ventilated Area: It is crucial to work in a well-ventilated area, preferably outdoors, to minimize the risk of inhaling toxic fumes and to reduce the risk of fire. Fuel vapors are highly flammable, and proper ventilation can help reduce the risk of fire or explosion.

No Smoking or Open Flames: Do not smoke near the vehicle or the fuel pump. Keep away from open flames or any potential sources of ignition, such as pilot lights, incandescent light bulbs, or electrical equipment. Sparks or flames can easily ignite fuel vapors, leading to a dangerous situation.

Use Proper Safety Gear: Always wear safety goggles or glasses to protect your eyes from fuel spills or splashes. Wear gloves and appropriate clothing to safeguard your skin and body from fuel exposure.

Disconnect the Battery: Before starting any work, disconnect the negative terminal of the battery. This will prevent any accidental electrical sparks that could ignite gasoline vapors.

Relieve Fuel Pressure: Always relieve the fuel system pressure before opening the fuel system. Releasing fuel under pressure can cause fires and injuries. You can do this by running the engine and pulling the fuel pump relay, or by pressing the Schrader valve on the pressure line to release the pressure.

Use Approved Containers: When draining or handling fuel, use approved containers such as a gas caddy or gas can. Never use unapproved containers that are not designed for fuel storage.

Have a Fire Extinguisher: Keep a fire extinguisher nearby that is rated for gasoline fires. This is essential in case of any accidental fires or fuel ignition.

Clean Spills Immediately: Have cleanup materials ready to clean any fuel spills or leaks immediately. Fuel spills can be hazardous and should be addressed promptly to prevent fires or environmental contamination.

Support the Vehicle: Use a jack or a support jack to lift and support the vehicle safely when accessing the fuel tank and pump. Ensure the vehicle is stable and secure before beginning any work.

Follow Vehicle-Specific Instructions: Refer to your vehicle's service manual or online tutorials specific to your car model. Different vehicles may have unique safety considerations or procedures, so it is important to consult these resources for additional precautions.

Be Thorough and Careful: Take your time and work carefully. Replacing a fuel pump can be a complex task, and rushing through it may lead to mistakes or accidents. Ensure you understand the process thoroughly before beginning the replacement.

Seek Professional Help: If you feel uncomfortable or unsure about any aspect of the replacement, don't hesitate to consult a professional mechanic. Some jobs are better left to experts, especially when dealing with flammable liquids and complex automotive systems.

Removing the fuel pump

Before you begin removing the fuel pump, make sure you are wearing protective clothing, such as gloves and goggles, and that you are working in a well-ventilated area. It is also important to note that you should never smoke near the fuel tank and to keep any sources of ignition away from the vehicle and fuel tank.

Now, to begin the process of removing the fuel pump, first, locate the fuel tank in your vehicle. This may vary depending on the model of your car, but it is usually at the rear, under the vehicle, behind a body panel, or under the rear seat. If your vehicle has an access door to the fuel pump, you can save yourself the trouble of dropping the fuel tank. Check your car manual for this information.

If your vehicle does have an access door, unplug the electrical connector and use a ratchet with an extension and a socket to remove the bolts holding the door in place. Keep these bolts in a safe place, then remove the door and look underneath. Here, you should see the top section of the fuel tank, along with the fuel lines and an electrical connector.

If your vehicle does not have an access door, you will need to raise the vehicle and secure it on jack stands. Block each front wheel with a wooden block to prevent the vehicle from rolling. Place a floor jack under the fuel tank, using a piece of wood to prevent damage, and raise the jack so that it rests against the fuel tank.

Next, remove the bolts from the fuel tank holding straps. You may need a ratchet with a long extension and, in some cases, a swivel joint to reach these bolts. Once the straps are removed, check if you can disconnect the fuel filling hose or fuel lines from the tank. Sometimes, you may need to lower the fuel tank slightly to access these hoses. On some models, you will need a fuel disconnect line tool to separate the fuel hoses.

Before disconnecting any hoses or lines, it is a good idea to tag them with masking tape for easy reference when reconnecting. Also, remember to disconnect the electrical connector from the tank; this powers the fuel pump.

At this point, you can drop the fuel tank. Cover any disconnected hoses with clean plastic and secure them with a rubber band to prevent contamination. Depending on your vehicle model, you may not need to completely remove the tank; instead, lower it just enough to access and remove the fuel pump or fuel sending unit assembly.

Now, to remove the fuel sending unit assembly, you will need to unscrew the cam lock ring securing the assembly to the tank. Use a brass punch or wooden dowel to avoid creating sparks that could ignite fuel fumes. Alternatively, you can use a screwdriver, but be sure to place a rag between the screwdriver and the lock ring tabs to prevent sparks. Rotate the lock ring counterclockwise to release it. On some vehicles, screws hold the fuel pump module in place, so you will need to unscrew these instead.

After removing the cam lock ring, slowly lift the fuel pump sending unit assembly out of the tank. Be careful not to damage the electrical mechanism connected to the long wire arm holding the fuel level float. Pay attention to the direction in which the long arm is pointing, as you will need to reinstall the assembly in the same orientation.

Finally, underneath the sending unit mounting bracket, you will find a rubber ring seal. Make sure to remove this ring and replace it with a new one when installing the new fuel pump.

Installing the new fuel pump

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 suitable workspace.

First, 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.

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

Now, install the new fuel pump into the assembly and reconnect the wires, hoses, new pump strainer, and bracket.

Before reinstalling the assembly, clean the inside of the tank with pressurized water to remove any dirt and let it dry thoroughly. Also, clean the fuel tank opening with carburetor cleaner before positioning the O-ring or rubber seal.

Install the assembly with the new fuel pump into 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, if you removed an access door, reinstall it.

Finally, connect the negative cable to the battery. Start the vehicle and check for leaks.

Relieving fuel system pressure

Before you start working on your vehicle's fuel pump, it is important to relieve the fuel system pressure. This is because the system operates under high pressure, even when the engine is shut off. Here are some common methods to relieve fuel system pressure:

Using the Fuel Pressure Regulator:

• Disconnect the negative battery cable with a wrench to prevent sparks.
• Locate the fuel pressure regulator on the fuel rail, which is mounted along the top of the engine. Ensure it is vacuum operated.
• Remove the vacuum hose from the top of the fuel pressure regulator by hand.
• Connect a hand-operated vacuum pump to the regulator and apply 16 inches of mercury (Hg) of vacuum to push the fuel back into the tank.

Using the Fuel Pump Connector:

• Access the sending unit/fuel pump assembly on top of the fuel tank. Some vehicles have an access door to the fuel tank, while others may require you to raise the rear of the vehicle with a jack to access the assembly.
• If there is an access door, remove the rear seat or the trim on the floor of the trunk to expose the fuel tank access door. Remove the mounting screws or pull the tape around the door.
• If accessing from underneath, ensure the vehicle is securely supported on jack stands before locating the fuel pump assembly.
• Unplug the fuel pump electrical connector on the sending unit/pump assembly.
• Start the engine and let it idle until it stalls, then turn off the ignition.
• Finally, disconnect the negative battery cable.

Using the Fuel Pump Fuse and Relay:

• Locate the fuel pump fuse, usually under the dashboard or in the engine compartment, often on the driver's side. You can also refer to your owner's manual for its location.
• Remove the fuse by hand or with a pair of pliers, or remove the fuel pump relay by hand.
• Start the engine and let it idle until it stalls.
• Disconnect the negative battery cable using a wrench.

Using the Ford Inertia Switch (for Ford vehicles):

• Locate the inertia switch, which is usually found in the trunk, rear compartment, or under the dashboard. This switch is designed to cut off fuel to the system in case of an accident.
• Unplug the electrical connector from the inertia switch.
• Start the engine and let it run until it stalls.
• Disconnect the negative battery cable.

Using the Test-Port Valve (for vehicles with a fuel injection system):

• Disconnect the negative battery cable and locate the Schrader valve (similar to a bicycle tire valve) on the fuel rail around the top of the engine.
• If there is a valve cap, unscrew it.
• Wrap a shop rag or rags around the port valve to catch any fuel that may squirt out during depressurization.
• Push the valve inward using a small screwdriver until fuel stops flowing through the valve.
• Replace the test-port valve cap if applicable.

Remember to always work in a well-ventilated area and keep a fire extinguisher nearby when working with fuel. Additionally, ensure you disconnect the negative battery cable before beginning any work on the fuel system for safety.

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's a step-by-step guide:

• Reconnect the negative terminal of the battery: This is important as it provides power to the fuel pump and other electrical components.
• Check the pump motor: Turn on the ignition switch and listen closely for the sound of the pump motor. The Engine Control Unit (ECU) energizes the pump motor to pressurize the fuel line when you first turn on the ignition. You may not hear the pump motor every time you turn the ignition if there is still enough pressure in the fuel line.
• Listen for a humming sound: If you hear a humming sound, proceed to the next step. If not, check the power connection to the pump. Ensure there are no issues with the connection. If the connection is fine, the new pump may be defective, although this is unlikely if you're using genuine replacement parts.
• Start the engine: If the engine doesn't start or runs roughly, proceed to the troubleshooting steps. If the engine starts and runs smoothly, you can skip the troubleshooting and move on to the next step.
• Connect a pressure gauge: If the engine isn't running smoothly, connect a pressure gauge to the fuel feed spout and turn on the ignition. The fuel pressure should be within the normal range specified in your car's service manual (typically around 49 psi for fuel-injected engines and 3-9 psi for carbureted engines).
• Check for leaks: If the pressure is low, there may be a leak in the fuel pump assembly. Common leak points include the pressure regulator O-ring, the pump nozzle O-ring, and the feed spout O-ring. Check these areas for leaks and repeat the pressure test.
• Complete the installation: If the pressure is within the normal range and there are no leaks, proceed to reinstall any remaining parts that were removed during the replacement process.
• Test drive the vehicle: Once the installation is complete, take the vehicle for a test drive to ensure it performs well under various driving conditions. Pay attention to any unusual noises or performance issues.
• Final checks: After the test drive, perform a final inspection of the fuel pump and engine to ensure there are no leaks or other issues.

By following these steps, you can ensure that your new in-tank fuel pump is installed correctly and functioning properly. Remember to refer to your vehicle's service manual for specific information and always prioritize your safety when working with fuel and electrical systems.

Frequently asked questions