Jaguar Repair: 1984 Jag xj6, gauge needle, wd 40

Question
QUESTION: Howard. The fuel gauges worked perfect when I first got the car. Now when it is switched to the left tank it registers about one eighth of and inch on the guage even though its near full. When switching from the left to the right or rt. to left the guage only moves about one eighth of an inch. Obviously there is power there but not an accurate measurement of whats in the tank. Any Ideas???
Roy

ANSWER: Hi Roy,

A common problem with the series III Jaguars is that the arm of the sending units rust and stick. I have been able to save about 50% of them by just removing them and with something like WD-40 and slow and careful moving of the arm, I was able to get them to free up and operate again.

It is unlikely the wiring but you can easily test that by having someone watch the gauge while you remove the sending unit wire while that tank is selected and note that the gauge needle will deflect all the way and then just touch the ground with the wire end and the needle should deflect all the way in the opposite direction. If it does that just remove the sending unit and note if the arm sticks or is stuck in one position.

Howard

---------- FOLLOW-UP ----------

QUESTION: Howard- where is the sending unit?  And is there one for each tank?
Thanks, Roy

Answer
Hi Roy,

The sending units are in the rear of the tanks behind each taillight assembly. If the tank is almost empty just jack the rear of the car up high and remove the tail light lens and then the assembly and remove the large ring holding the sending unit in by rotating it. Be sure the ignition is off at this time because any spark at this time could end your car and you too.
If you need to drain some fuel out of the tank the drain plug is in the bottom under a large plastic plate.
Be careful not to damage the float or wire arm when removing the sending unit. The unit plate is keyed so it will only fit back in one direction.

Howard