We've tested the pump right when we walked out the parts store and it turned on. We'll check it again after running some errands first. This problem is bumming me out, but its a old truck with many stock componets. I will also start testing the wires from the inertia switch to the tank selector switch to the pump. I think also the sending unit was never replaced.

 

Obviously the red wire going into the tank harness supplies 12 volts. Using a voltage meter or a test light have someone try to start the engine will you test for voltage. I am assuming that you know how to use a meter or light.

 

The diagram in post #14 above does not apply to your truck.
Here is a diagram of your trucks wiring and wire colors.


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Good news I hope, did some testing on the tank selector switch. Red/Yellow wire powers for a second from inertia switch. Tested the rear pump wire the Brown/White has power then I tested the solid Red wire nothing. Used a jumper wire and connected the red/yellow to the solid red wire and she primed up then ran. Heading to the junkyard for another switch since I spent enough money. I bought a new tank selector the first day...wondering why it didnt work.Wish me luck

 

Problem solved, wasn't the tank selector switch but the wires that connect to it. Took a small screwdriver and pulled each wire out and cleaned them with a wire bush. Also pulled each wire from the pump connection and cleaned them up, bent a little tab to make a snug fit. Ran all day yesterday with no problem switching tanks.

I would like to thank everyone for helping me out. I'm heading out for a trip today and wanted the truck running for my grandparents so they don't have to have trouble driving our extended cab long bed dually truck.

 

When I bought my new tank, the pump and sending unit had a big gob of dielectric grease on it. Might do well to put some on before you put the bed back on it.