How to Replace the Fuel Pump in Gmc Cars

by Contributing Writer; Updated June 12, 2017

The fuel pump in a Gmc car is in the fuel tank. When the fuel pump goes out, the fuel tank has to be pulled down to get the pump out of the tank. A new fuel pump will include an O-ring, the pump and a strainer. Replace these parts as the fuel pump assembly is pulled out of the tank. The fuel filter should also be replaced to give the whole fuel system a tune-up.

Under The Hood:

 How to Replace the Fuel Pump in a GMC Jimmy

Run the fuel tank empty, if possible. The Jimmy's tank does not have a drain plug, but if the pump is still operating, then it is the only method of running the tank dry. An empty tank is lighter than a full one, and it makes removal easier.

Unbolt the fuel tank's protective shield by turning its hex-head bolts in a counterclockwise direction. The shield will then slide out. With it removed, the tank's bolts are now accessible.

Disconnect the electrical and fuel line connections to the tank's fuel pump, located on the top center front of the tank. There are two (or three) different-sized fuel lines, and one wiring adapter plug that must be disconnected. The hoses come off by pinching or unscrewing their hose clamps, and the plug simply pulls free once its catch is depressed.

Unbolt the fuel tank by turning the bolts that hold it to the frame counterclockwise. The tank should be supported with a jack during this process, as once the tank is freed it will drop from the frame. Lower the tank out of the truck, and use the jacks to set it aside to work on it.

Unscrew the two screws holding the fuel pump to the tank by turning them in a counterclockwise direction. Once they are out, the pump can be gently pulled upwards and out of the tank. Some residual fuel may spill out, so have a towel handy.

Replace the fuel pump by lowering it into place inside the tank, then securing its screws in a clockwise direction. The plastic fuel pump may be easily damaged by turning the screws too far, so only tighten them enough to seal the pump to the tank.

Replace the fuel tank into the truck with the jack(s), and tighten the bolts that secure it to the frame in a clockwise direction.

Reconnect the fuel lines and adapter plug. The fuel lines are sized for their nipple fittings, and should only fit onto the nipple that they were designed for. Tighten each one with a hose clamp. The wiring adapter plug should make a "snap" sound when it is properly seated.

Fill the tank with fuel and test the new pump. The pump should make an audible whine as the truck is started, and the whine should stop after a couple of seconds. The pump might make a softer sound after the truck is started--this is normal.

Items you will need

  • Socket set

  • Wrench set

  • Drain pan

  • Jacks and jack stands

 How to Replace the Fuel Pump on a 1991 GMC Sierra Truck

Park your Sierra on a level surface and set the parking brake.

Locate the fuel tank in the back of the Sierra. Place a jack under the tank. Raise the jack to the bottom of the tank. This will help to bring the tank down when the straps are removed.

Unbolt the two straps holding the fuel tank in place with a socket wrench. There is a bolt on each end of the two straps. Lower the fuel tank onto the jack. Do not lower the tank until all the wires and hoses are disconnected.

Access the electrical connector at the top of the fuel tank. Raise the locking tab and pull the connectors apart. Pull the vacuum hoses off the lines by hand. Disconnect the fuel lines from the top of the fuel tank. The fuel lines will have a quick-disconnect fitting. Squeeze the fitting and pull off the fuel line.

Unscrew the hose clamp on the fuel filler pipe at the back of the fuel tank with a flat-head screwdriver. Pull the hose off the tank.

Lower the tank to the ground. Pull the tank off the jack and out from under the Sierra.

Unscrew the retaining ring at the top of the tank with a flat-head screwdriver and a hammer. The screwdriver will act as a punch. Strike the end of the screwdriver with the hammer in a counterclockwise motion . Once the retaining ring is loose, pull off the fuel tank.

Pull the O-ring off the threads and replace with a new O-ring. This will prevent leaking when the fuel tank is filled up.

Lift the fuel pump out of the tank. Pull it out at an angle, as the sending unit will obstruct it from coming out straight.

Pull the cylinder-shaped fuel pump off the assembly. Disconnect the electrical wire at the top of the pump. Replace with the new pump. The pump will clip into place. Screw the strainer into the bottom of the pump. The strainer will bolt into place. Connect the wiring harness to the top of the pump.

Insert the fuel pump assembly into the fuel tank. Place it at an angle so the sending unit does not get bent.

Thread the retaining ring by hand. Tighten the ring by pushing it with the screwdriver and hammer.

Place the fuel tank on the jack. Slide under the truck. Raise the fuel tank high enough to connect all the wiring and hoses, which will lock in place once they are attached to their respective connections.

Slide the fuel filler hose onto the back of the fuel tank. Slide the hose clamp over the hose and the piping. Tighten the hose clamp with a flat-head screwdriver.

Raise the tank the rest of the way to its mounting position. Bolt the two straps by hand to ensure that all four bolts are started correctly. Tighten the bolts with a socket wrench.

Pull the jack and the tools out from under the truck.

Add fuel to the tank.

Turn the ignition key to the "Start" position. The fuel pump will run for three seconds and shut off. This will prime the fuel system.

Start the Sierra and allow it to idle for five minutes. Inspect the fuel tank for leaks while the truck is running. Turn the engine off.

Items you will need

  • Jack

  • Socket wrench

  • Socket set

  • Flat-head screwdriver

  • Hammer

 How to Replace the Fuel Pump on a Yukon

Relieve pressure in the fuel tank by removing the gas cap. Raise the hood and locate the fuse and relay box on the driver's side over the front wheel. Consult the legend on the inside of the cover and remove the fuel-pump relay fuse; pull it up and out of the retainer with your fingers. Turn the ignition and attempt to start the car; if it runs, allow it to stall. Turn off the ignition. Remove the negative terminal clamp from the battery with an adjustable wrench.

Remove the fuel from the fuel tank, using a siphoning kit. Pump the fuel into an approved container and store in a safe place away from sources of fire or spark.

Raise the rear of the car with a floor jack and place the vehicle on jack stands. Locate the EVAP canister next to the fuel tank. Remove the quick-connect hoses from the canister by squeezing the tabs together and pulling the hoses out. Remove the canister-mounting-bracket bolt with a socket wrench and then remove the EVAP canister.

Disconnect the fuel supply and return lines from the fuel tank, using a GM fuel-line-separator tool kit. Remove the fuel filler and vent hoses by unscrewing the clips with a flat-head screwdriver and pulling the hoses off.

Place a transmission jack under the fuel tank and raise the mechanism so it supports the fuel tank. Disconnect the fuel-tank straps by removing two bolts with a socket wrench. Lower the tank a few inches and remove the electrical connectors, fuel-level indicator and fuel-pressure sensor; squeeze the plastic tabs and pull the connectors out. Lower the jack and remove the fuel tank.

Release the locking tab from the fuel-pump module by prying it up with a flat-head screwdriver while turning the retaining ring counterclockwise with a pair of wide-mouth, groove-joint pliers. Carefully remove the fuel-pump module from the tank.

Install a new seal on the new fuel-pump module. Align the fuel-line fittings and seat the module in the tank. Engage the locking tab and replace the retaining ring by turning clockwise with the groove-joint pliers.

Follow the directions in reverse order to reinstall the fuel lines and fuel tank. Replace the fuse, fuel and battery clamp and start the car to test the new fuel-pump module.

Items you will need

  • Jack

  • Jack stands

  • Adjustable wrench

  • Socket set

  • Groove-joint pliers

  • Fuel-siphoning kit

  • Fuel container

  • GM fuel-line-separator tool kit

  • Flat-head screwdriver

 How to Replace a Fuel Pump in a GMC Sierra

Determine which fuel pump your GMC Sierra will need. This depends not only on the make and model, but also the engine size. Models are equipped with a Vortec 4.3 L, 4.8 L, 5.3 L or 6.0 L engine, depending on the exact model.

Use a socket wrench to disconnect the negative battery cable. Relieve the fuel system pressure, drain and remove the fuel tank. Use a fuel tank sending unit wrench to remove the retaining ring for the fuel sender assembly and discard the seal.

Note the position of the fuel strainer before pulling it off and discarding it. Unplug the electrical connection for the fuel pump and the fuel level sensor under the cover of the fuel sender.

Remove the retaining clip for the fuel level sensor and remove the fuel level sensor by squeezing the locking tangs. You may now remove the fuel pressure sensor.

Install the new fuel pump using the items included in the kit, especially the seal and fuel strainer. Tighten the mounting bolts for the fuel tank straps 30 foot pounds.

Complete the installation by reversing the removal procedure. Turn the ignition on for 2 seconds, off for 10 seconds and start the engine to check for leaks.

Items you will need

  • Fuel pump kit

  • Fuel tank sending unit wrench

  • Socket wrench set

  • Torque wrench

About the Author

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