my full gauge is stuck above full does anyone know what it would be and easiest way to fix it?

 

My 88 is doing the same thing. My problem is the sending unit. There is somewhere on here a post that said to unplug the wires to the pump and sending unit and use a jumper wire on the wires going to the front of the car and if it goes m/t then its your sending unit. I could have just explained it wrong. The sending units for the 3rd gens are kinda pricey too