Hi I am trying to figure out what is wrong with my gas gauge it will only go up to 3/4 full it won't go up to the top even when I fill up the tank. Do I need a new wire or is the hand sticking?

 

Probably sending unit going bad...

 

I dont think ive owned a first gen that didnt do this lol

 

The sending unit probably has a worn wire pickup spool. Common actually. Replace the sender. You can pull it and test it per the FSM. If you need the resistance values let me know and I will post them for you.

 

Sending unit may be fine. The tank level is based on the resistance value the gauge sees from
the unit. If the unit doesn't get good grounding it will always read low. Turns out that corrosion
in the sending unit between the outer fastening and the innerfastening gets corroded and limits
the affectivness of the ground to the tank via the little screws that hold the sender in.

I fixed this on mine by jumpering a wire from the base of the sender as it comes thru the plate
over to one of the screws. Now it reads full when I fill it.

 

So it is either the whole sending unit or a bad wire from the sending unit?