Gauge reads 1/4 tank with ignition on, no matter how much gas is in it. Disconnect ground and gauge reads past full. Dropped tank and sending unit is good. Must be gauge? What now? How do I prove?

 

With the ign key on, if you ground the gauge wire at the tank does it go to E? If so it is sender or ground wire to sender related.

 

I don't understand. Please describe more thoroughly what we are doing and how we are proving that it is not the gauge. I am missing something.

 

There is a, I believe tan, wire that connects to the float/sending unit at the tank. Remove that wire from the sender and with the key on and the wire not connected to anything the gauge will read past full. If you then take that same wire and touch it to the metal chassis the gauge will read empty. The fuel sending unit is a float with a rheostat (0-30 ohms) attached to it that changes resistance and loads the gauge down to read the fuel level. If the gauge functions the way I described the wiring and the gauge is good. Your problem is the sending unit.


Looks something like this:

 

If the gauge is the problem where can I get it fixed?

 

Can't answer that, but maybe one of the guys stuck in the 50's can. I've always gotten another one.

 

Try Fusick Automotive Products for a fuel sending unit. Part numberFTU578....https://www.fusickautomotiveproducts...nts.asp?dept=8.. but try and find out if it is the gauge or the sending unit.

On the 55 year cars(may be the same on 58) the clamp that holds the ground wire often corrodes and provides a poor ground, it grounds through the gas line of all things, check to see if that could be the problem....Tedd

 

What is the best way to get at the fuel gauge to replace it?
Thanks for any suggestions.

 

You gotta drop the tank and it won't be fun.: I believe there is a drain plug on your tank that will help you get it dry but if it is like a 55 you need to get the car off the ground quite a ways, a lift will always make the job easier so you can wrangle the tank and filler stem from around the springs and frame.

I always wondered if a 4 inch hole could be cut in the trunk floor like an inspection plate and the sending unit replaced from the top... Just a thought...Tedd

 

If by chance it turns out to be a faulty dash gage ,CollectorsAutoSupply has one listed online for $160. Hope you are lucky and find a bad ground at the tank unit. Larry

 

Continuing this thread, I have a similar problem. Gauge tests out fine using instructions above. Sending unit bench tests (0-30ohms). Put the pieces all together and the gauge never goes above 1/2. We replaced the sending unit. Same results. Dropping the tank again, I'm thinking this is a grounding issue.


Frank

 

Ignachuk, my 58 Olds gauge situation is the same as yours. What did you find as your solution????

 

I'm pretty sure it's the gauge itself. This weekend I hope to take it out, clean it and test it.


I'm a strong believer in closing out a thread, so as soon as I reach a conclusion, I'll post the results.


Frank