my gauge is all hooked up in the back of the cluster. it reads full for about 40 miles or so i would say then just drops to zero gas i dont get it
Sounds like possibly the sending unit inside the tank is bad, the winding on the sender the floats rubs up and down on to read the resistance may be worn, worn through, or broken
truth, my old 77 had a spot right in the middle where the wire was broken, gauge worked till it hit the half mark and then dropped to empty. I just lived with it and filled the tank after so many miles.
Your gonna have to drop the fuel tank to access the fuel sender unit, on the newer trucks like yours (88)? there should be 2 cover plates on the top of the tank, the smaller one is the sending unit, the larger the fuel pump. You would use an ohm meter to check the sender resistance as the float is moved up and down to determine if its good or bad.