Fuel Gauge Reads Empty

[GraniteCow]

The fuel gauge in my 1996 XJ reads empty when it’s not even close to empty. If I pull out the sending unit and move the float around it gives accurate readings as long as it is outside the tank, but goes back to empty when I reinstall it. Sometimes it reads full when the tank is full, but goes to empty when there’s still 10-15 gallons left. Right now, the tank is completely full and it reads empty with the low fuel light on. I already replaced the sending unit with a new one and the behavior is exactly the same. The only thing I can think of is the floats don’t float in a modern gas/ethanol blend. Has anyone encountered this? Any ideas on how to fix it?

 

[Anak]

I do not know what path that circuit takes, but I would suspect something like a ground problem or a loose connection that is somehow related to the position of the wires when installed. Perhaps a chafed wire or something pinched?

Or could it be a mechanical problem at the pivot? Has the hole the arm pivots in become enlarged or misshapen such that natural movement of the arm is unable to rise? Hmm... thinking about your description of symptoms and the fact this is common to two units probably scratches that idea. Nevermind.

I would put my efforts into studying that circuit and trying to figure out what could be wrong there.

 

[SlowXj]

I would think grounding or .... The float is filling up with gas ... I've seen that happen on some older stuff...

Sent from my SM-G950U using Tapatalk

 

[lawsoncl]

The fuel level sensor and the pump share a common ground, so probably not a bad ground. Try measuring the sensor resistance right at the connector outside the tank.

Copied from https://www.cherokeeforum.com/f2/fuel-sender-reesistance-135163/

"96 SM calls for 20 ohms full/ 270 ohms empty, plus/minus 5%. The Renix and HO senders operate in opposite fashion."