Filled up yesterday. When drove to supermarker on full. Start after shopping and just above E. Swerved, braked and found a pot hole. No change. In 6 mile drive home slowly went from E to 1/2. Parked and restarted. Went right up to F.
Not planning on doing anything if does not repeat. Anyone have an explanation?

 

I can’t help with a knowledgeable answer to your specific question, only can add that my fuel gauge (2002 XKR) is as crazy as the average mother-in-law, and has been no use at all since I bought the car 8+ years ago.

it may show full when I know that the tank is full. Or it may show 3/4 full. After a few minutes of driving it may show much less than I know it should, or maybe just a little less. I never know what to expect.

To wit, it never show the correct level UNLESS I’m on a long trip and the constant vibration of hours and hours driving does something positive to the gauge system. On those long distance driving situations it’s darned near perfect, from F all the way to E.

I’ve learned to use the “gallons / fuel used” indicator on the dash info display to inform me of the “real” gas level. It is ALWAYS perfection. I zero it in (with the trio odometer) at each gasoline fill up.

For example, if it subsequently displays that I’ve used 13.7 gallons when I’m pulling in for a new top-off of gasoline, I’m confident that the tank will hold exactly that amount. No more and no less. It’s never been wrong.

With that kind of dependability over the last 8+ years of ownership, I’ve been putting off working on my gas gauge accuracy, or lack thereof.

Z

 

It's almost certainly your fuel level sender that is sticking - if you select the Range display on the dash (as above like zray's fuel used indicator) you can confirm its the sender rather than a fault on the fuel gauge itself. Range should show a big number after you have filled up, which gradually falls as you use the fuel - if not, its the sender that is faulty.

 

+1 on the faulty fuel level mechanism. Luckily it's relatively easy to access. Just make sure you replace it with 1/4 tank or less.

 

Worked fine since OP. No plans to do anything if does not return. I've done pumps and sender on a 2003 XJR (no tank side entry like earlier years). No fun. If have to do on X308 find someone with tiny hands to release the fuel lines.

 

Causes of failure are ....
The wiper that runs over the resistance wire looses contact at some points.
The float gets punctured or saturated with fuel and does not float consistently.
The float arm has bent and is catching on the tank internals
Voltage stabilizer for the gauge is faulty /intermittent