While driving, suddenly the fuel gauge failed and displayed zero fuel.
When I got home: I remove the crimp wire from the fuel float and touch it to ground and the fuel gauge showed full tank, OK the fuel gauge and circuit is working, as there are only 3 basic components to the fuel gauge system it would be simple to solve.
1. I checked the earthing of the fuel float screw and body - good and well grounded.
2. I removed and replace it with a new fuel float and again check the screw and body - good and well grounded.
3. Turned on the key - fuel gauge still not working.
4. Next, I replace the fuel vibrator with a new one -- No good, fuel gauge still not working.
5. I removed the fuel float, fuel vibrator and hooked it up on the bench with a spare fuel gauge display - working well, so the problem is not with the vibrator, the float or the fuel display, a bit stump here?
6. Hook everything up again on the car, recheck all wires and earthing of the fuel float body and screw but why isn't the fuel display working? And on instinct -- I hooked a earth wire from the fuel float screw directly to earth and walla... the fuel system worked.
7. Hook back all the original 35 years old fuel components and it worked as well -- in the end, the fuel system just need an additional earth wire connected to the fuel float screw/body. I have checked and counter checked many times the fuel float screws and body and they are well connected to earth with hardly and resistance...but why it didn't work is a bit strange.