If you unhook the wire at the sending unit, check in the trunk at the center in the rear for a connection. When the wire is unhooked and the key on the gauge should read passed full. Now ground the wire going to to the gauge and with the key on it should read empty. If it passes the test it will be the sending unit or tank ground. If it does not then it will be wiring to the gauge or the gauge. How does it act when you fill the tank and use the first half? The sending unit works on 0-30 ohms 0 being empty and 30 is full. You should have 12 volts at the wire you unhooked from the sending unit.
