fluctuating fuel gauge

A

artron9

Senior Member
Another concern for my 52! The fuel gauge needle is wandering between 1/2 full and 1/4 full. I'm sure the general consensus might be to replace the unit in the gas tank? However, I was thinking of removing the unit and cleaning it since it is not that old. Do you think it would help? Also, can I access it from the top of the tank without removing the tank? Thank you for your input!
 
"since it is not that old."??? How do you know how old it is? Yes, it can be removed from the top of the tank without removing the tank. Just lift up the mat in the trunk for access to it. I suspect the float will have to be replaced...
 
Thanks Petehoovie. Its about a year old. Had it in the shop for a tank cleanout and seal.I'm sure you are correct but i will pull it out and check it. Thanks
 
artron9 said:
Thanks Petehoovie. Its about a year old. Had it in the shop for a tank cleanout and seal.I'm sure you are correct but i will pull it out and check it. Thanks
Click to expand...

Ok, I have a question. What would cleaning the tank out have to do with the fuel sending unit? Was it replaced at that time with a new unit? If so it is most likely a resistance unit now.
 
Most likely problem is that the brass float on sending unit has developed a hairline crack allowing fuel to seep inside. This causes faulty readings. You can repair it yourself by soldering or you can buy a new float from C and G. Be very gentle with the sending unit.

Good used replacements are very hard to find. New OEM units are made of "unobtainium".
Make sure it's grounded and all connections are clean. The OEM 6V sending unit looks similar to this one. They don't operate on "the ohms resistance principle".

Be sure to post a photo of what your sending unit looks like. It might be an aftermarket repro. that claims it will operate properly. Truth is, they don't as the OEM gas gauge and sending unit were made by King Seally and operate on a bi-metallic heat principle, not oms law. If you do a search on "gas tank sending unit" you'll find pages of discussion. The replacement units that operate on Ohms Law Principle will not read properly with the OEM fuel gauge that operates on the "bi-metallic heat" theory.
 

Attachments

  • IMG_9093b.jpg
    IMG_9093b.jpg
    119.6 KB · Views: 25
  • IMG_9097B.jpg
    IMG_9097B.jpg
    52.6 KB · Views: 25
  • IMG_9101B.jpg
    IMG_9101B.jpg
    64.4 KB · Views: 28
Last edited:
JSeery, thanks for your comment. The tank was removed and cleaned. A new sending unit was installed in the tank at that time. Not sure what you mean by "a resistance unit now"?
 
The Ford fuel gauges operate on a system of bi-metalic strips and points, to oversimplify it. The sending units commonly available today operate on a variable resistance system. The two operating systems of gauges and senders are not interchangable. Most who have to use a resistance unit keep experimenting with the sending unit until it is fairly accurate as the tank nears empty. This is all assuming that you are using an original Ford gauge.
 
About the only replacement senders available are resistance type as opposed to original pulse-current type. 19Fordy posted some about this. It is somewhat hit and miss on getting the resistance units to work correctly.
 
Too bad you don't still have the original sender. They can sometimes be repaired. Much better unit.
 
Thanks 40CPE, 19FORDY,JSeery. I'm very clear on how the sender functions. thanks for your concerns. I will gently remove it and see what is going on. Maybe they never replaced it and the original is still in there?
 
If you find the sending unit to be OEM, you can gently pry off the top cover and turn the star wheel to finely adjust. Turn star wheel clock wise will move the needle towards FULL. Turning it CCW will move it closer to EMPTY. BE VERY,VERY GENTLE. Don't break any wires or that carbon resistor. Here's a start.
https://www.fordbarn.com/forum/showthread.php?t=268805&highlight=gas+tank+sending+unit

Type Gas Tank Sending Unit into Search Box for more info. It is possible to adapt another year King Seally Ford Lincoln, Mercury gas tank sending unit if you can't find one specifically for your car.
 
Last edited:
You must log in or register to reply here.
Back
Top