Replacing The Fuel Pump In Your Classic 79 F150 Truck

Replacing the fuel pump in a 79 F150 is a complex process that requires careful attention to detail. While the pump itself is not particularly difficult to replace, accessing it can be challenging. This is because the fuel pump in the 79 F150 is located inside the fuel tank, which means that either the fuel tank needs to be dropped or the pickup bed needs to be removed to reach the pump. This process is made easier with an extra pair of hands and a safe lift to support the vehicle. Once the fuel tank is accessible, the pump can be replaced by following a series of steps, including disconnecting fuel lines, cleaning the fuel pump module, and installing a new fuel pump assembly.

Disconnecting the fuel tank

First, remove the negative battery terminal with an 11mm wrench. Loosen the fuel filler neck bracket from the metal line, and then loosen the vent hose bracket from the metal line. Remove the vent hose from the tank, and disconnect the sensor. Disconnect the fuel pump connector, and remove the locks from the fuel lines with a flat-bladed screwdriver. Disconnect the pressure and return lines with a disconnect tool.

Now, you will need to remove the fuel tank straps. There are two straps, and these can be removed with a 13mm bolt. Gently twist them off to avoid damaging the mounting point. At this point, you will need an extra pair of hands to help you lower the fuel tank. As you do this, about halfway through, disconnect the fuel fill line with a hex socket.

With the fuel tank disconnected, you can now access the fuel pump module, which is bolted to the top of the fuel tank. The next step will be to clean the module before removing the old fuel pump assembly.

Removing the fuel tank

To remove the fuel tank from a 1979 F150, you will need an 11mm wrench, an 8mm socket and ratchet, a flat-bladed screwdriver, a disconnect tool, and a 13mm bolt. You will also need a safe lift to support the truck, and a friend to help you.

First, disconnect the negative battery terminal with the 11mm wrench. Loosen the fuel filler neck bracket from the metal line, and the vent hose bracket from the metal line and the tank. Remove the vent hose from the tank. Disconnect the sensor and the fuel pump connector. Remove the locks from the fuel lines with the flat-bladed screwdriver, and disconnect the pressure and return lines with the disconnect tool.

Next, loosen the 13mm bolt from one side of the strap and let it hang down. Remove the 13mm bolt from the second strap. Now, lower the fuel tank down with the help of your assistant.

If you are working on a 1999-2014 F-150, you will need to siphon the gas out of the tank before removing the fuel tank. You will also need to remove the heat shield with an impact wrench, and place two floor jacks underneath the fuel tank to support it when it drops.

Disconnecting the fuel pump

Firstly, ensure you have the necessary tools for the job. You will need a flat-head screwdriver, an impact wrench, and a hex socket. It is also recommended to have a safe lift to elevate your truck and provide easy access to the fuel pump.

Now, let's get started with the process:

• Siphon the fuel: Use a clear hose and an air pump to siphon the gasoline from the fuel tank. Store the fuel in a safe container. This step is crucial for safety reasons and to prevent spills.
• Remove the heat shield: Use the impact wrench to remove the bolts holding the heat shield in place. Be careful not to confuse these bolts with the ones that secure the fuel tank. Gently set the heat shield aside.
• Support the fuel tank: Place two floor jacks underneath the fuel tank to support it when you start removing the bolts and straps. You can also add padding to the jacks to avoid damaging the tank.
• Disconnect the fuel pump lines: There is a fuel pump module bolted to the top of the fuel tank. This module has safety clips that secure the fuel lines. Use a flat-head screwdriver to carefully release the clips and disconnect the fuel lines from the module.
• Clean the fuel pump module: Before removing the old fuel pump assembly, use a plastic brush to clean off any dust or dirt from the module. This step will help prevent contamination of the fuel tank when you remove the old fuel pump.

By following these steps, you will have successfully disconnected the fuel pump in your 79 F150. Remember to work carefully and safely throughout the process, especially when dealing with gasoline and the vehicle's electrical system. Always refer to a qualified mechanic or a detailed repair manual for additional guidance if needed.

Removing the old fuel pump assembly

To remove the old fuel pump assembly from your 1979 F150, you will need to first ensure that you have a safe lift in place to support the truck, as you will be spending a lot of time underneath it. You will also need a flathead screwdriver and an impact wrench.

Begin by siphoning the fuel out of the fuel tank using a clear hose and an air pump. This step is crucial for safety reasons and to avoid spilling fuel. Once the tank is empty, remove the heat shield with the impact wrench. There are two sets of bolts here: one set holds the heat shield, and the other set holds the fuel tank in place. Be careful only to unfasten the bolts for the heat shield.

Next, place two floor jacks underneath the fuel tank to support it when you drop it. You can add padding to the jacks to prevent any damage to the tank. Now, unfasten the bolts holding the fuel tank in place and gently twist off the two straps to avoid damaging the mounting point. As you lower the fuel tank with the jacks, have an assistant help you, and about halfway through, disconnect the fuel filler line with a hex socket.

With the fuel tank now accessible, you can begin to disconnect the components connected to it. Disconnect the fuel pump lines from the fuel pump module, which is bolted to the top of the fuel tank. These lines are connected by safety clips, which you can release with a flathead screwdriver or a 3/8” Ford fuel line disconnect tool.

Now, you are ready to remove the old fuel pump assembly. First, unfasten the six bolts that hold the module onto the fuel tank. Then, twist the old fuel pump assembly out of the tank. If it gets stuck, use a flathead screwdriver to pry it up gently.

Be sure to install the new fuel pump assembly in the reverse order of removal, reconnecting the fuel lines and electrical connectors correctly.

Installing the new fuel pump assembly

Now that you have removed the old fuel pump assembly, you can install the new one. This process is the reverse of the removal process.

First, lower the new fuel pump assembly into the tank. Ensure that the arrow on the new fuel pump is aligned with the arrow on the tank. Reinstall the six hex bolts that secure the fuel pump assembly.

Next, reconnect the two fuel lines to the new fuel pump assembly. A flat-head screwdriver will help with the retaining clips. Then, reconnect the electrical connector.

Finally, reconnect the negative battery cable. Reinstall the bed or tank and test the new fuel pump. It is normal for the truck to turn over more than usual during this first start as air is purged from the fuel line. We recommend cycling the keys to the "run" position several times for 10 seconds at a time before cranking the engine.

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