The GMC Jimmy/Blazer SUV was manufactured with a tank-mounted fuel pump which can malfunction or wear out, requiring replacement. Unfortunately, the fuel pump is located on the top of the fuel tank in most models, and it necessitates removing the fuel tank completely for access. The average backyard mechanic can replace a fuel pump in a Jimmy in about an hour.
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.
