Recently, my fuel gauge has started to do something strange. About 3 tanks ago I noticed that after I filled up, the gauge only went about 2/3 of the way back up. I tried turning the car off and starting again since this fixes some things but nothing. Then as I drove home (about 45min) the gauge slowly crept up and returned to normal after a while. I didn't think much of it at first (just a Jag quirk) but then it happened again, and then a third time yesterday. Each time, the gauge goes about 2/3 of the way back then stops, then after a bit of time it goes back to normal. It doesn't seem to matter whether the car is running or not because the second time I filled up, drove for about 5min then parked for a while and when I came back, the gauge was almost all the way back to full. So the car doesn't have to be running to fix the problem. Anyway, I was wondering if anyone has any ideas? Since it does eventually get back to full, I'm assuming that everything is working but maybe there is a problem with the fuel level sensor or something. I haven't tried the most common fix for these things (disconnect the battery) since I haven't had a chance and the weather has been really bad but that is the first thing on my list. Could it be a bad sensor or something?

 

This may sound silly, but try bouncing the back of the car after a fill up. If it goes to full, it's probably a sticky float. I looked up the 03 STR fuel system in this handy dandy Jaguar CD Service Manual I recently got and it shows that both fuel pumps contain conventional floats. It sounds like a sticky float. That happened to my old Cougar way back when. Ended up having to pull the pump to fix it.

 

As jeff said they have 2 pumps, when i got my car i noticed different behavior then what you note but none the less odd. they ended up replacing one pump and that solved it.

There are also a couple of other things that could cause it but i forget the particular parts replaced when mine was having problems. Im pretty sure my tech said you have to remove the back seats.

so check your fuel pumps first!

 

Yep the pumps are under the back seat and two 10" round twist off covers.. The sending unit is what actually goes bad, but I think its connected to the pump..

 

I had an identical problem late last year. Mine (06 3.0) was going from 3/8th's to full, back and forth. Since it is still under factory warranty, I took it to the dealer to fix it. Here's what the work order stated:

"Checked codes, got B2627, B1202. Checked raw fuel thru inst. pack. Raw 1 91; raw 2 255.2 Open circuit. Gauge was reading full but dropped to 1/4 tank. Checked resistance at pump. RH side at 300 ohms and left at 3.6 kohms. Replaced both pump and jet pump."

Part #

(1) XR852870 ASSY SENDER
(1) XR852864 SENDER
(1) XR848118 GASKET

The bad news is that the "service advisor" said it would have cost around $900 if out of warranty.

 

Well, the problem is gone! I figured that it must be a sticky float since the car had sat in the ditch on a side angle for about a day before this happened (rain + -7C = 1/2 inch of ice on the roads!, I don't recommend even attempting to leave your driveway with these conditions. Stupid me). So, I ran the tank to basically completely empty (I think I only had about 1 liter left in it) then I filled up and kind of bounced the rear end as much as I could. I figured that doing this would give the float a full range of motion and hopefully unstick it. Got in the car, turned it on and presto! Fuel gauge to full. I have filled up since then and works fine. So, for anyone else who has this problem, before you sell a kidney to get it fixed, try the simple solution! Worked for me!

 

Wow... I didn't think it would actually work.... but thought it was worth a shot.... :0