Jaguar Repair: fuel gauge on 87 XJ^, gauge needle, open tank

Question
When I purchased this car a couple of months ago - it had been stored for the winter with the gas tanks drained.  The gauge for one of the tanks worked, but has since quit.  Is there anything I can do?  How would I determine if it is the float in the tank or the gauge?  If it's the floats - what would I co to fix it?

Answer
Hi Bill,
When the tanks are drained and empty the sending units are exposed to air and moisture and are pron to rusting. The gauge sending units are switched when you push the fuel tank switching valve button on the dash. If the gauge needle moves to the empty position on either tank and you know you added fuel to that tank than it is most likely rusted in the empty position. This is true on both sides or either side. If you turn the ignition on and the gauge stays off scale it can be the gauge or the switch.
You need to drain the tank on each to take out the sending unit to see if it can be repaired or needs replacing. Jack the rear of the car as high as you can and remove the tail light assembly to gain access to the sending unit. Remove the wires and bump the retaining ring around to get it to release and just pull the sending unit out. I have been able to repair about one out of three I have tried to repair by wetting them with WD-40 or any penetrating oil and slowly wiggling the arm up and down. Be careful if you try to operate the unit out of the tank as any small spark close to the open tank can cause an explosion of the tank. I have done that by finding something that fits tight into the opening of the tank, then reconnect the wires and try to operate the unit by hand.
I hope this helps, let me know.
Howard