GAS GUAGE

[smurfee]

  When I put gas in my 57 ( doesn't matter how much - 5 to 20 gallons ) my guage goes to full & stays there until I am down to about half a tank, any ideas - THANKS, SMURFEE 

[JPotter57]

Probably a bad voltage regulator on the back of the instrument cluster.  If not that then a flaky fuel level sender.

[Ford Blue blood]

I would look at the sender...the voltage regulater also provides power for the temp gauge.  If it is acting normal most likely the regulater is OK.

[JPotter57]

Thats true, if it was bad, all the gauges would swing to the max position.  My last truck did that a while back, I had an extra instrument cluster, so replaced the whole thing, then worked properly.

[Hoosier Hurricane]

Smurfee:

Maybe you have an intermittent ground problem at the tank, and the weight of the gas makes or breaks the ground.  Try a jumper wire from the sending unit to a good body or frame ground.

John

[Ford Blue blood]

Smurfee got to thinking about this problem.  If you have a loose ground the gauge will read empty, a short will have it pegged full.  Ground the temp gauge lead at the sender for about 3 seconds and watch the needle swing to hot then do the same with the fuel gauge at the sender.  If it swings just like the temp gauge did that will confirm the gauge, wiring and voltage chopper (regulator) all good.  That leaves the sending unit in the tank.