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.
If you going to replace the fuel pump:
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.
After two tanks of fuel has gone through, replace the fuel filter.
Good luck and hope this helps, Note the bolt that holds the gas tank strap may strip or snap. Just cut it off and replace by welding a new bolt for the gas tank strap.