I have 2001 xk8 66 thousand miles and this just started happening for me as well. Twice in one week where the reaches less then 1/2 but after a restart it reads again. So I am not sure of it is the float. Am I correct in assuming the float should stay stuck.

Just thinking this one through out loud, especially after Doug's post above. On my car the fuel guage does not reset, or perhaps I should say does not "display" any increase if I leave the ignition on while filling it. In other words if I pull into gas station with 1/4 tank, have them fill it up but leave the ignition on the whole time, like I tend to do to "Reset" the odometer, the guage will show an unchanged 1/4 tank through the entire fill up cycle. Here's a key point - at the same time (ignition on, guage = 1/4 tank, trip computer reset) - the "remaining miles" properly shows 340+ miles. The trip computer knows there are 19.9 gallons in the car even while the guage is unchanged at 1/4 tank. In other words, this proves to me that the display is not directly tied to the float position in this case. As soon as I cycle the igntion off/on the fuel guage is reset to the correct position. Hope this helps you guys with the trouble shooting.

thanks I will try that next fill up

Is your float accessed from the outside of the tank? I have a procedure that will help but if your float is inside the tank you will need to identify the leads outside to do this. I hope this helps.

Link. http://jagrepair.com/FuelTankSendingUnit99XK8.htm

Did any one ever figure out this issue;I.e., fuel gauge drops to empty and low fuel light comes on after a small amount of fuel is burned.
My 2001 convertible has this issue. Thanks.

Mine DOES reset if I leave ignition on while refueling. 2001 XK8 convertible-58,600 miles.However, after next shut off, gauge drops to empty and low fuel lite comes on and it stays that way until the next fillup. When the issue first arose, it was erratic- gauge would work, then stop working then start working again. Now it doesn't start working again until tank is refilled. Help!!

mine is different. I get to about 3/8 ths of tank a little over 10 gallons used I go to empty then my mileage expected gets an error. i can turn off and back on resets and gets to empty.

My 97 xk8 has an intermintant empty reading accompanied by the low fuel light. There are 2 wires attached to the sending unit in the tank. when the guage is working and I have 1/4 tank of gas, and the wires connected to the sending unit, one wire has 2.5 volts on it and the other about .2 volts. The resistance of the sending unit is 730 ohms with the tank 1/4 and the wires off the sender. when I put a 80 ohm resistor in between the 2 wires in place of the sender the gauge reads full tank. I assume from this that the sending unit is just a variable resistor with a range from 80 to ?? ohms.
The only thing different from all the other sending units I've seen over the years is that does not have one side of the resistor connected to ground, hence the 2 wires.
I wired in the 80 ohm resistor and will drive this way for a few days and see if the gauge stays at full. If It does i'll pull the sender our and check it out. BTW my car is a convertable, but the sender is accessible through the trunk!

My Sending Unit failed the same as yours. I bought a new one and installed it, fixing the problem. Of course, you must make sure the Fuel Level is below the Sending Unit position to avoid spillage.

A ohm meter showed intermittent operation on the original unit.

I took the original unit and re-soldered the connections where the wires connect to the tabs. The repair worked and I would recommend that you try that first before buying a new unit.

there are 2 wires going to the sender
if you put a 80 ohm resister in place of the sender terminals you should get a full reading. If this is solid for a few days, replace the sender.
chuck

Is this what you are talking about

Link JagRepair.com - Jaguar Repair Information Resource

Hey all, I recently had kinda-sorta the same problem on my 98 XK8. When I started the car I noticed that the fuel gauge was reading as full when I knew that I only had about a quarter of a tank. I shut the car down and the needle went down to the 3/4 mark when it should have dropped all the way down to E when off. I restarted and it went back up to full. Scrolling to the range remaining showed me around 140 miles, so I knew that was off as well (for me a quarter of a tank is around 80-ish miles range). Of course I came straight to the forums and tried to figure out what was going on and it appeared that the sending unit was probably the likely culprit so I steeled myself to get ready to replace it. I watched the youtube video of the gauge problem in this thread and saw a comment there from another owner who said he fixed the issue by disconnecting and reconnecting the battery, thus resetting the computer. I figured I had nothing to lose so I gave that a shot and lo and behold, it worked! Hopefully it's not just temporary, but the gauge and the Range remaining indicator are both reading correctly now. It probably won't work in all cases, but at least give it a whirl before you start breaking out your wrenches!

Well done....