1993 GMC Sonoma Replace the Fuel Pump
The fuel pump in the GMC Sonoma is positioned in the fuel tank. The pump pushes the fuel from the back of the truck through the fuel line and to the engine. Replacing the fuel pump requires lowering the fuel tank and pulling the pump out of the tank. The pump sits in an assembly that also contains a strainer and a sending unit that controls the fuel gauge. The strainer acts as a filter and keeps debris from getting into the fuel line.
 Tools Used
|Flat head screwdriver|
|New fuel pump|
 Replace the Fuel Pump
Removing the Fuel Pump
- Ensure that the truck is parked on a flat level surface. Set the parking brake. Chock the front wheels.
- Open the hood to access the engine compartment. Disconnect the battery cables with a socket wrench.
- Raise the back end of the truck with a jack. Raise the truck high enough to place jack stands under the axles. Lower the truck onto the jack stands.
- Locate the fuel tank under the truck toward the rear. The fuel tank is held on by two straps. Place a jack under the tank to support it.
- Unbolt the straps with a socket wrench. There will be two bolts for each strap. Allow the fuel tank to settle on the jack. Lower the jack to access the top of the fuel tank.
- Disconnect the wiring at the top of the fuel tank. The connectors have locking tabs that need to be pried up to be unlocked. Pull the connectors away from each other. Pull the fuel lines off the tank with your fingers.
- Locate the hose connected to the back of the fuel tank. Unscrew the hose clamp with a flat head screwdriver. Pull the hose off the back of the fuel tank with your fingers.
- Lower the fuel tank to the ground. Slide the tank off the jack. Pull the tank out from beneath the truck.
- Access the fuel pump by unscrewing the top of the fuel tank. Tap the tabs on the top of the fuel tank with a flat head screwdriver. Strike the screwdriver with a hammer to push the assembly loose. Ensure you are pushing it counter-clockwise. Pull the assembly out of the fuel tank once it is loosened. You may have to tilt the assembly to the side to allow the sending unit to clear the tank.
- Disconnect the electrical wire at the top of the fuel pump. Pivot the pump out of the assembly and pull the pump away from it.
Installing the Fuel Pump
- Attach the new fuel pump to the assembly. Ensure that the new strainer is attached. Screw the strainer onto the pump with a screwdriver. Push the electrical connector onto the top of the pump.
- Replace the O-ring on the cover with a new O-ring. Position the assembly on top of the fuel tank. Hand tighten the assembly onto the fuel tank. Push the assembly tight with a flat head screwdriver and a hammer. Push the assembly clockwise.
- Place the fuel tank onto the jack. Push the tank under the truck and lift the jack up to position the fuel tank. Leave room to attach the wires and fuel lines.
- Push the fuel lines onto the piping by the fuel pump assembly. Connect the wiring connectors. Push them together until they lock in place.
- Push the large hose onto the back of the tank. Push the hose clamp over the hose and the pipe. Tighten the hose clamp with a flat head screwdriver.
- Raise the jack to position the tank. Bolt the straps to the frame to hold the tank. Tighten the strap bolts once all of them have been started.
- Raise the back of the truck with the jack. Pull the jack stands out from under the axle. Lower the truck to the ground.
- Connect the battery cables to the battery. Ensure that the red cable is attached to the positive terminal. Tighten the cables with a socket wrench.
- Turn the key to the "start" position. Leave the key in this position for five seconds. This will activate the fuel pump. Once the fuel pump has cycled, turn the ignition key to start the truck. This process may take a couple of attempts, as there is air in the fuel lines. The truck will start once the air is evacuated from the air lines.
- Allow the truck to idle. Inspect for any leaks.
 Tips & Warnings
- You can purchase the fuel pump and the O-ring at automotive parts stores.
- To make installation of the fuel tank easier, empty the gas tank into a drain pan once the cover is removed from the gas tank. Pour the gas from the drain pan into a gas can. When the installation is done, pour the gas back into the tank via the fuel filler. This truck does not offer a drain plug on the gas tank.
- Use caution when working under the truck. Ensure that the front wheels are chocked and the parking brake is set.
- Use caution when working with gasoline, as it is highly flammable and toxic.