Hey 3window!
First, check all of your connections and make sure that there is no corrosion and that everything is grounded properly. Then, do the following tests:
1. Remove the wire from the sending unit on the gas tank and ground it to the frame of the car. Turn on the ignition switch. If the gas gauge shows full the wire from the gas gauge to the sending unit in the tank is open circuited. If the gas gauge shows empty, the wire is fine, but the sending unit in the tank is open circuited and should be replaced.
2. When the gas gauge shows empty under all conditions, it may be caused by the wires being reversed on the gas gauge.
3. Disconnect the wire from the gas gauge leading to the sending unit in the tank and turn the ignition switch on. If the gauge shows full the gas gauge is okay. If the gas gauge still shows empty, the gas gauge is defective.
4. Reconnect the wire to the gas gauge and disconnect the wire on the gas tank sending unit. Turn on the ignition switch. If the gas gauge shows full, the wire between the gas gauge and the sending unit in the tank is okay, but the gas tank sending unit is defective. If the gas gauge shows empty, the wire from the sending unit is shorted.
Good luck!
