I have no further wisdom to offer. I don't know, do new cars have a mechanical fuel level sender in the tank? I'd supposed they'd need to. So maybe, as like an old Dodge I had many years ago ('69 Coronet) where the gauge read wrong at the halfway point... I pulled the float assembly and the coil area was all kinds of twisted and awry. Probably different systems nowadays, but maybe could still be the in-tank sensor.....????

 

They do still have a mechanical fuel level sender. The problem with the XK is that EVERYTHING is in the top of the fuel tank - sender, fuel pump, the lot - and the only way to access it is to drain then drop the tank, which entails some dismantling of the subframe as well; it won't be cheap...

Be damned if I can think what it might be, though. Bent arm on the sender? Unlikely - the car's only done 17,000 miles. Damaged sender resistance wiring? Again unlikely, for the same reason. Car been standing for long periods with the fuel tank less than full, leaving deposits on the sender resistance wiring? Possible, maybe, but that would prevent it reading towards the full end, not towards empty.

I know about the problem. If ever the mileage readout goes wrong, I'll be in trouble, but until then, I can live with it - I just fill up at around 250-275 miles done. Who knows, it may start working properly again...

 

Well, it's still doing it, but I've noticed that if it is reading about 3/4 full with the car level when I start the car, after I've been driving for a few miles it reads around 7/8 full or a touch higher, still with the car level. That suggests to me that the problem is electrical.

We all know how easy it is to diagnose weird minor electrical glitches. I guess the car will still have the problem when the next owner gets it....

TN

 

1st it is interesting that this problem came up after a battery issue and was not resolved with the battery replacement. Also did you have an opportunity to have the dealer check it on their system to see if there is a SW issue or if there is a reset procedure. Also is there a way to check the gauge package in the dash. Last I just took a look under my car and the gas tank removal doesn't seem like to big a deal. From what I see you need to remove the exhaust , heat shroud and drive shaft. Also the fill hose but it appears that the tank will drop out without removing any structural members.

 

Does the XK have "anti slosh circuitry" to prevent the gauge [LCD readout] from moving quickly when fuel sloshes around in the tank? I am traveling now and don't have my schematics to check. The XJS's that I had used the "anti slosh circuitry" to dampen the
gauge reading when the sender was moving quickly with the fuel sloshing. This module/circuitry was a problem on the XJS which resulted in flakey gauge readings.

I would think this would be done digitally in the ECU now instead of on the analog side at the sender. But, with Jaguar, who knows?

 

There was never a problem with the battery on the car; I only disconnected it, on advice from the forum, to see if it would fix the problem, but it didn't. The symptoms would suggest, to me at least, that the signal from the fuel level sensor is being corrupted in some way, and since the indication increases as the battery becomes 100% charged as the car is driven, it may well be that the two are connected. If it's a coincidence, it's a consistent coincidence...

I don't think there is a problem with the instruments; the problem is consistent, and the estimate of distance to empty is plainly based on the received fuel level signal. The fuel consumption on the trip mileage is consistently about 10% too optimistic ( no surprise there; my Mercedes is a little optimistic too) and the odometer reads correctly.

I don't have the facilities to remove the fuel tank myself, and I wouldn't pay to have it done unless I was pretty sure it would enable the problem to be fixed.


Davchr, I'd be very surprised if the damping of the fuel gauge was not part of the ECU, but I bear in mind that the electronics on the XK are really Ford, not Jaguar.

I'll live with it for the moment. It's only a niggle, not a serious fault, and now that I know about it, I can easily drive round it. My own generic code reader doesn't bring anything up, but next time the car goes into a Jaguar specialist I'll get the codes read. It may be quite a while, though, as I do most of my routine maintenance myself.

 

My 2002 XK8 coupe (US specs) has exactly the same issue, ever since it sat for a while & the battery went completely flat. If I fill the tank, the gas gauge shows around half full and the range display starts at around 180 miles & drops like a stone. Any advice/input welcome!

 

Do a Hard Reset.

 

Paul,
+1 on Cee Jay's advice. Do you realize that you're in the wrong Forum for your 2002 XK8? This is the X150 Forum, for 2007-2015 XK/XKR models. Your car is the previous generation X100, and you'll get more and better replies here:
Jaguar X100 XK8 Forums
Stuart

 

Thank you both for your invaluable advice - and my apologies for posting this on the wrong forum! By coincidence, the gas gauge/range display started gradually righting itself during a long trip yesterday - as some above had said might be the case -, but then the transmission failed (luckily, close to home). So, my XK is currently laid up 'til I raise the funds for a rebuild/replacement. Thank you again!