I have a '56 F100. How do I test the gas guage to know if it works? I know my sending unit is broken and would like to know before I buy a new one if my guage is broken too. It is a stock set up.

- Paul

 

If you take the "hot lead" wire (from the gage) from the tank sender and put it straight to ground, the gage should peg to full. That will tell you the gage is OK.

You say you know your sending unit is broken. How do you know that? You could just not be grounded from sender to chassis and you would get no reading. The sender just basically is a variable resistor to ground.

You can do a test to check: Remove the sender from the truck. Hook the hot lead from the gage to it (or use a jumper) and put a jumper from the sender ground to a good chassis ground. Then move the sender arm to see if the gage reacts.

Your float could be leaking also. If it is, the sender would be reading empty all the time. But a leak is not difficult to fix.

Overall, this is a fairly easy system to fix and calibrate.

Good luck.

 

Try Not To Make Sparks Around The Gas Tank When Testing The Sending Unit.
We Hate It When A Tank Goes Boom And Sends A Member Into Orbit.

 

the reason i state the sending unit is broken is because physically you can see that - the arm and float appear to have been broken off and the top part of the unit is rusted thru. i will test this weekend