My gas gauge stopped indicating the fuel level. I checked the fuel sending unit and it was working. The fuel level sending unit had 30 ohms resistance when full and the low level showed infinity at the sending unit terminal. I went through all of the termination points looking for a loose connection. I think the loose connection was the connectors on the sending unit. After tightening all wiring connections the fuel gauge started working, however the gauge reading showed 1/2 full when the tank was full. I drove the car for several miles before the gadge started to go down, then I drove several more miles after the gauge indicated zero fuel then finally the low level warning light came on. I think I touched the fuel level indicator arm on the gadge and changed the settings. How do I get the indicating arm back to show the correct level? I upgraded the instrument cluster lighting to LED and added a green LED between the fuel gage and oil pressure gage that was not in the original installation to make the instrument lighting brighter and uniform like the other two gauges that had green lights next to the oil and fuel gage . The speedometer gage had two green lamps at 180* from each other. The tachometer gage only had one lamp in the upper right corner so I added an additional lamp holder 180* from the existing lamp to match the speedometer gauge for brighter and uniform lighting.

 

See this thread:
https://www.jaguarforums.com/forum/x...ng-fix-267848/

In addition it is highly likely that your sender is also faulty, eveb if it is giving a reading of sorts.