1988 Chevy Blazer

I looked at s-series. Take fuel pump connector loose. Use a resistor between wire terminals for sending unit, One wire is pink, the other black. Among other places, radioshack sells resistors, don't cost much. Ohms/resistor specs, same thing. See below. With key on, you don't have to start, if the gage reacts properly to resistor, I think the problem is the sending unit in the gas tank.