Fuel gauge (on the instruments panel) always shows empty.

Anybody had this issue? What are the steps to troubleshooting?

 

Probably just the cluster ground. You can check the fuel tank sensor by removing it and using a voltmeter to check if it has a lower/higher reistance when moving it. But it is mostly the ground connection.

 

The fuel tank sensor that is inside the fuel tank?

 

Yep. Behind the board at the rear. Should have 3 plugs on it.

 

Or the float has broken off or become so saturated with fuel that it's always sitting on the bottom. Consult Palm's book for how to take it out, it's not a bit deal (just don't try it with a full tank).

I've followed Palm's suggestions, and while it's more accurate than it was before, I still has some issues, mainly it doesn't show full when the tank is full.

Good luck,

John
1987 XJ-S V12

 

The gauges are so often flakey that removing the cluster to clean ALL contacts points and grounds, and add a redundant ground, is good to do just on general principles on any XJS, IMO.

I'd never trust the temp gauge, in particular, without some sort of independent measurement of coolant temp.

As for the fuel gauge, grounding the light green/orange sending unit wire should result in the needle going right to the top. If it does the gauge is at least fundamentally operational and focus can turn aft....sending unit and/or wiring. Sending unit failures are as common as cluster problems

Cheers
DD

 

Thank you gents! Starting with the instrument panel seems like a logical place.

 

Before doing that, it would be worth removing the spare wheel and accessing the sender terminals (see pic). By VERY briefly grounding the two powered terminals you can ask a helper to see if (a) the low fuel light flashes on and (b) the gauge flicks up to full.
If they do, the problem is the fuel tank sender. If they do not, the problem is (a) between the sender and up to and including the instrument cluster; or (b) the sender inside the tank - the bit you have not tested - AND possibly still the rest of the system. This test only shows IF the cluster circuit is working, and if it is, saves you a seal of grief removing the instruments.
Greg

 

John
I had exactly this problem too, and I followed the Great Palm's advice about cleaning the electrical path through the actual fuel gauge BETWEEN the flexible circuit board and the instrument windings. This path involves tiny screws that have to carry tiny current as a secondary task, and tiny pieces that the screws connect to that need careful cleaning. White tablecloth on a kitchen table precision job! But it worked, and the gauge now shows its full travel, to both the top and the bottom of the scale.
Greg

 

Did this test. Did not have an assistant today, but i was able to see the panel from the back while grounding the terminals. The result:
- the low fuel light did come one
- the fuel gauge did not move (as far as I could tell)

Removing the instrument panel is the next step, I assume...

 

take the green with a black stripe off the tank unit and earth it if the gauge goes to full its the tank unit If it doesn't move your in trouble.

 

Just re-did the test again. (My wire was not green with black, but green with white.)

This time the gauge did move to the full (max) position!

(I guess I was not able to see clearly first time while fiddling with both hot wires. This time I focused on only one wire and I used clips for better connection.)

Ok, this means the gauge in the instrument panel is probably fine. The problem is with the sender unit in the gas tank?

 

As long as the fuel level is about half or lower you can remove the sending unit from the main tank as Greg illustrated. I suggest removing the battery first though to eliminate the possibility of a spark. Gas fumes and electricity is a bad combination. The three wires connect to the sending unit in L to R order of Black, Green, Red. Unplug them. Loosen and remove the retaining ring. A flat head screw driver will pry loose the plate from the gasket. Gently maneuver the sending unit out of the hole. The float arm may just be stuck or the wire connector may have broke. If that's the case you'll need a replacement. New ones are not too expensive. About $50.

 

Thanks. Will do that.

At this point I don't really know how much gas is in the tank. When I first got the car I thought gas tank was empty (because the gauge showed empty), but the Low Fuel light on dashboard was not lit. So, I put in about 10 gallons at the closest gas station. But since the fuel gauge did not move at all, I figured it was not operational. So, I don't really know what was the level before adding 10 gallons...

But I think I can figure out how to guesstimate whether gas is almost empty or almost full. Maybe I can feed a rope or something like that through. Unless somebody can suggest an alternative (easier) method

 

A option is to drain the tanks but you need a low pan with a fair amount of capacity unless you can get the car elevated.

Under the battery is a sump tank. On the bottom of the sump tank is a drain plug. it can be accessed by removing the round black plastic grommet. The grommet can be pried off from the under side. Once you have access to the drain plug you can get a deep well socket on it to loosen it up. It may be fairly hard to break free initially. Once loosened you can attach a hose to the tube and then hand loosen the plug to let the fuel start flowing.

Another option is to siphon gas out thru the filler neck into a gas can, bucket(s) or other storage container.

All you really need to do is get the fuel level below the fuel sending unit access port. By loosening the sending unit retainer ring and carefully prying up (start from the top) the sending unit you'll be able to see if fuel is leaking out. There is a rubber gasket to seal the sending unit to the tank. If so tighten things up and drain/siphon some more fuel out. Repeat until sufficiently lowered.