Sending Unit or Fuel Gauge

[D'Animal]

My CJ-8 fuel gauge has decide to read half full when it is empty.

I dropped the tank and cleaned all the contacts on the fuel sending unit. I put it all back together and it will read full but quickly goes to 1/2 and stays there for the next 200 miles. I ohm check it and it varies depending on the position of the float.

I dropped the tank again and install a new sending unit for the 22gallon tank and it does the same thing.
It reads full when it's full but after a short period of driving, it's reading half full on the gauge. It stays there until it is empty and the engine dies.


Has anybody seen or ran across a bad gauge?


Any suggestions?

 

[General Sherman]

usually a bad ground. It can be at the guage or at the sending unit. Try at the sending unit first. Don't asume the ground is good just because it looks good. Run a new gound anyway. The guage works on Ohms of resistance and a ground working half a$$ will vary the resistance drastically. I've had good luck running a new grond at the sending unit without disconnecting the original. You cant over ground it.
Good luck

 

[Campfire]

I just had to replace the sending unit in the Willys. Check the resistance from the sender to ground. After a lot of research, I found that Jeep/AMC uses a different ohm set up. Here's what I've found
GM 0 ohm = empty / 90 ohms = full
Ford & Chrysler 73 ohms = empty / 10 ohms = full
AMC/Jeep & Stewart Warner 240 ohms = empty / 33 ohms =full
So be sure to get the right sending unit, or your gauge will never read right.