Hi All,
Just replaced fuel filter on my 2004 XJ8 at 180k. When I start the car now, the gauge drops 1/8 tank! No fuel is leaking at the filter. When I shut the car off, I hear fuel dripping back into the fuel tank. After a while, I restart the car and the level is back up an 1/8 tank, which then drops back an 1/8 tank again. Where are these 2-3 gallons going? How do I fix it?!
Thanks!
Rob

 

Sorry I dont have an answer, but this one is going to be good to follow!

 

Whether this would cause the issue I dont really know however my first thought would be if it were me "did I install the fuel filter the correct way round?".

 

I assume that you have a 4.2 litre engine since you are in the USA.

I believe that you have two fuel pumps not just one and a jet pump.

You have a NRV (check valve) in the pipe work in the tank which could be leaking and

faulty senders are a known problem due to corrosion of the contacts.

New senders are not expensive and clip onto the fuel pumps.

 

Hi Rob,

Obviously you aren't gaining and losing 1/8 tank of fuel, so as meirion1 suggests, the most logical explanation is that the fuel level sender is misbehaving.

On our '04 XJR, when the fuel level is below about 1/4 tank, the reading on the fuel gauge doesn't vary noticeably, but the computer estimate of the driving range will vary up and down by 50 miles or more. My assumption is that our sender is misbehaving, and for now I'm just living with it.

I don't know why changing the fuel filter might be cause this behavior, but if the old filter in your car was original, at 180K, it may have been partially or substantially obstructed. I just changed the fuel filter in a friend's '06 XJ8 at 97K and it was utterly black on the inlet side. Perhaps now that you have a new filter the fuel pump is running more freely than before and that is somehow contributing to the sender's change in behavior?

Cheers,

Don

 

Hi Folks,
And Happy New Year!
Thanks for the feedback on this odd situation, folks. I had wished it was trapped air that would slowly bleed-out by now, but it doesn't seem to be the case.
Don, your personally observed 50-mile range is indeed the difference between my trip computer's estimated range and my (suspect?) actual fuel level gauge measurement; so to be safe, I've been conservatively refilling based solely on the estimated range. This is my second fuel filter change, as I had done one prior at 120k without any issue. That time, I had installed a WIX filter, and this one was a NAPA Gold one (NAPA said it was better than WIX brand).
Jackra_1, the filter orientation was the second point I confirmed upon this one happening; checking for fuel leaks about the new filter was the first point. We've all overlooked things before, so for that I thank you for pointing this out, for sure.
Meirion1, I do believe my tank has two fuel pumps, as it straddles the propeller / drive shaft. While this is a better C of G location than standing upright behind the rear seat, it reminds me of my wife's former Bimmer E46, where replacement & dealer calibration of replacement fuel pumps with integral senders was a required "maintenance item" every 100k (OEM quality excuse & a "nuisance item", but they never asked me for mine!). I hate cracking open my diesel tank on our boat for fall clean-outs - the odor never relents, despite being aired-out all winter. Nevertheless, like the E46, are the No Return Valve, senders, & fuel pumps accessed by removing the rear bench seat?
Rob

 

Yes, very much like the E46!

 

"Are the No Return Valve, senders, & fuel pumps accessed by removing the rear bench seat?"

That is correct-

info here:

https://www.jaguarforums.com/forum/x...removal-19489/

 

I think it's only the supercharged engine that has two fuel pumps ?