fuel gauge issue

[willtoliv]

New guy here! Just got my 98 XK8. It has a few issues (I expect that). My question, I have intermittent fuel gauge response. I fill it up and it shows empty for a day or two then corrects. It also shows an error message that the range is faulty. Would I look to connections at the tank sensor or elsewhere? I appreciate any help. Cheers Willtoliv

[H20boy]

hmmm, glad my gauge is a little more reliable...I can't personally assist you on this one, but I think I've heard of a few guys around here with sender issues. Hang tight, you'll get some more replies soon.

[willtoliv]

Thanks, this is a very impressive site. I'm looking forward to contributing.
Will

[2003 XK8]

welcome to the club. before I bought my 2003 XK8 i thought that jaguar would have worked out all the screwy electrical problems they have ALWAYS had with their cars but, as most of us know, they haven't.

I've heard that the fix is to replace the sending unit in the tank. Apparently this is a simple thing to do if you have a coupe; if you have a convertible, i'm told you need to remove the fuel tank which not many people seem to want to do.

Be aware that if your fuel guage isn't reading correctly, your driver information center info is probably not right either - mine sure isn't. So don't rely on the RANGE or MPG info it gives or you just might get stranded by running out of gas.

[theweeb]

Just to throw in here, mine started acting up just last week. Sometimes at vehicle start, it would peg way over full at the 2 o'clock position and take a couple of dances with the key on/off to get it to jump back down; sometimes it stays on empty. The range on the dash computer seems to show true, but I have started keeping the tank topped off just to be safe.

Question: If it is the sending unit on the tank, wouldn't that information be used to calculate the range, and thus show up as near zero when the gauge shows empty? This leads me to believe the problem is in the dash, not the tank, but then, I am fairly new to this

[SeismicGuy]

You just have to end up accepting the fact that these cars have more tics than a cheap hotel room in New York. Among those that I have had are:

• DSC warning that will come on randomly when starting the car and then go away after that
• SRS light that was random and then stayed lit (this was recently resolved)
• memory seat position circuitry that does not always bring things back to the correct position
• low fuel warning light that came on one time AFTER completely filling the tank

I suspect a lot of modern cars that are filled with computer controlled sensors and servos have similar problems with quirky behavior but this seems especially true of our cars.

Doug

[oldmots]

I always try to remember that when participating on forums, tying the problem list to reliability of the car in general will give a distorted viewpoint. These cars are very reliable and well made, they are complex and things do fail, sometimes due to poor maintenance or other causes, sometimes due to design or build quality. Some of these cars are getting to be geriatric and you can only expect so much from an old high performance car that typically gets flogged a little more than some wagon family truckster.

[pophen]

Oldmots, well said! Jack

[2003 XK8]

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[2003 XK8]

Originally Posted by theweeb

Question: If it is the sending unit on the tank, wouldn't that information be used to calculate the range, and thus show up as near zero when the gauge shows empty? This leads me to believe the problem is in the dash, not the tank, but then, I am fairly new to this

i don't think so. If I fill the tank and my fuel gauge stops at 1/2, the Driver's Info shows about 1/2 the range I would expect. If the gauge later creeps up the scale, the RANGE also increases on the Driver's Info display. Even if he gauge appears to be reading correctly and it has been zero'd, the Driver's Info always displays higher MPG than my manual calculation (the manual calculation is correct based on the gallons to fill the tank and the odometer).

I've had my gauge near the zero mark and the amber light come on and a fill-up took only 15 gallons (squeezing the pump to shut-off 4 to 5 times), so i really had almost 5 gallons still in the tank ....

[2003 XK8]

Originally Posted by SeismicGuy

...I suspect a lot of modern cars that are filled with computer controlled sensors and servos have similar problems with quirky behavior but this seems especially true of our cars.

Originally Posted by oldmots

... you can only expect so much from an old high performance car that typically gets flogged a little more than some wagon family truckster.

without continung a difference of opinion, I'll just say that:

- if my jag had the quality of a $20k honda or toyota it would be an improvement; actually the same was true of my (now gone) 91 Sovereign and my 96 XJR .. c'mon - the state of the art in automotive technology in 2003 (!) can't make a reliable GAS GAUGE ?!?!?

- the '71 Chevelle SS i had as a kid was an old performance car, not my 2003 XK8; my car came from Beverly Hills and went back to the selling dealer in Hollywood for EVERYTHING including wiper blades - flogging and family wagons are in a different world ....

[theweeb]

Originally Posted by 2003 XK8

i don't think so. If I fill the tank and my fuel gauge stops at 1/2, the Driver's Info shows about 1/2 the range I would expect. If the gauge later creeps up the scale, the RANGE also increases on the Driver's Info display. Even if he gauge appears to be reading correctly and it has been zero'd, the Driver's Info always displays higher MPG than my manual calculation (the manual calculation is correct based on the gallons to fill the tank and the odometer).

I've had my gauge near the zero mark and the amber light come on and a fill-up took only 15 gallons (squeezing the pump to shut-off 4 to 5 times), so i really had almost 5 gallons still in the tank ....

This is of course your experience; I will attempt to take a picture of the fuel gauge at empty and the Driver's Info showing 280+ miles to show you mine. I think we are probably dealing with several causes that manifest in different ways.

As for the other comments on this issue vs. reliability, I can only say that in spite of the initial problems I had with the car and the subsequent "personality traits" that I now have adjusted to - like the exploding center console cup holder - I absolutely love this car and am thrilled every time I get behind the wheel. True.

[2003 XK8]

Originally Posted by theweeb

This is of course your experience; I will attempt to take a picture of the fuel gauge at empty and the Driver's Info showing 280+ miles to show you mine. I think we are probably dealing with several causes that manifest in different ways.

I guess it depends whether or not you still had gas left . If so, it sounds like maybe the Driver's Info works from the sender in the tank and your gauge is bad.

Originally Posted by theweeb

As for the other comments on this issue vs. reliability, I can only say that in spite of the initial problems I had with the car and the subsequent "personality traits" that I now have adjusted to - like the exploding center console cup holder - I absolutely love this car and am thrilled every time I get behind the wheel. True.

Yep - no self-respecting japanese auto maker would build a console like that. But don't worry, after you get it back together it will squeek like an old rocking chair every time you put your arm on it.

i find these cars easy to love and also easy to hate. After getting rid of my 1996, I was hoping to see improvements in my 2003 but, in a lot of ways, there's the same old crap ....

[randyb]

Originally Posted by 2003 XK8

i don't think so. If I fill the tank and my fuel gauge stops at 1/2, the Driver's Info shows about 1/2 the range I would expect. If the gauge later creeps up the scale, the RANGE also increases on the Driver's Info display. Even if he gauge appears to be reading correctly and it has been zero'd, the Driver's Info always displays higher MPG than my manual calculation (the manual calculation is correct based on the gallons to fill the tank and the odometer).

I've had my gauge near the zero mark and the amber light come on and a fill-up took only 15 gallons (squeezing the pump to shut-off 4 to 5 times), so i really had almost 5 gallons still in the tank ....

That is a myth, you cannot fill the tank upto the same point you filled it up on you last fillup. Unless the tank is completely empty with each fillup and you are using a non-pressure fill hose.
The pressure varies inside your tank and the pump could cutoff at 9 gallons onetime and at 9.9 the next, making you think your gas mileage went up, when it did not. I know this because a friend of mine does the fuel validation for central Florida and one of the tests he does, is to fill a tank and see where the fuel pump shuts off and he does this for two reasons, one to check and see that the gas in the tank, matches the reading on the pump and that the pump does not overfill. He does this test 3 times and he says he rarely gets the same results.

So unless you had mythbusters fill your tank, I will trust what the car says. No offence is meant.

[Reverend Sam]

I disagree with randy. Once you remove the filler cap the pressure in the tank equals atmospheric pressure. That friend that does the fuel validation for Florida might be noticing a difference of a tenth or two, but it's not going to vary by a gallon. And that has more to do with the foaming of the gas as it is squirted into the tank. The foam on top of the gas is highly variable, so the vacuum activated cutoff mechanism might pick up more foam one time and less foam the next. That's why after the pump cuts off I always give it a few seconds for the foam to settle down. Then I slowly put in more gas until the little cutoff hole is actually sucking in gasoline, not just foam.

[randyb]

Originally Posted by Reverend Sam

I disagree with randy. Once you remove the filler cap the pressure in the tank equals atmospheric pressure. That friend that does the fuel validation for Florida might be noticing a difference of a tenth or two, but it's not going to vary by a gallon. And that has more to do with the foaming of the gas as it is squirted into the tank. The foam on top of the gas is highly variable, so the vacuum activated cutoff mechanism might pick up more foam one time and less foam the next. That's why after the pump cuts off I always give it a few seconds for the foam to settle down. Then I slowly put in more gas until the little cutoff hole is actually sucking in gasoline, not just foam.

You misread what I said, I did not say atmospheric pressure. I was talking about the amount of pressure caused by the gas going into the tank.
Secondly, most people probably do not fill upto the cutoff hole.
Also, do you shake the car to get any air pockets out?

Also, I do not know what the test tank looks like, but I know him to be not prone to flights of fancy.

[theweeb]

. . . have not found the cause of this intermittent fuel gauge issue yet, but here is a (crappy) cell phone picture of the range computer working as it should even though the gauge shows empty.

[theweeb]

Yesterday this one happened, fuel gauge pegged way past full (did not know it could go that far). Fascinating problem....

[OregonJag]

My money says you've got a bad servo in the gas gauge or a loose connection to the instrument cluster as you stated in your first post. The info panel below the speedo would have a different line running to it and they both would use the same sending unit in the tank for fuel level info. If you use your "fuel used" information instead of the gas gauge aren't your fill ups mostly accurate?

[theweeb]

Originally Posted by OregonJag

My money says you've got a bad servo in the gas gauge

Thank you, that makes the most sense. Repairable? I will do a search...