The truck is a 94, 2500, with about 160k, and we are not the original owners. The truck will not run. It seems to be a problem with the fuel system somewhere. We replaced the fuel filter, and then the truck would run (detonation occured) as long as the key was in the START position, but when it was in the RUN position it immediately dies. After doing this for awhile we took the filter back off and noticed that is was only half full, we had filled it up before we put it on. The next thing that we changed was the lift pump it still did not seem to help, or to put out enough fuel. Pushing on the primer button draws up more fuel than turning the engine over. We thought that the lobe inside the engine might be worn so we built the pump shaft up about an 1/8". Still no difference. The lines from the tank to the pump have not been changed but I have not noticed any fuel on the frame or ground that they may be leaking. Any help would be greatly appreciated.

 

Your problem sounds like the shutdown solenoid to me.
The lines can leak too and get air sucked in without dripping or showing any leakage. I don't think it was a good idea to put something on the pump lever- if the cam is worn you already have lost the hardened surface.

AlpineRAM