Just obtained a replacement tank for the cat and I found these inside the threaded holes - my old tank didn't have and they aren't listed anywhere as an available part.

They are fibre of some sort not rubber - if they weren't circles with no obvious join I'd say leather ... anyone come across these before. Just to confirm they are in all the threaded holes of the fuel tank - well not all because one is on my desk ...

 

Not all pre-facelift tanks have those. The ones that do use a different outlet outlet and return pipes than those that don't. On my '85, the original tank had those, but the new, aftermarket replacement tank, even though it was the same part number tank, did not. The tanks that don't use those use brass olives instead. See if your old pipes fit the replacement. I believe the two types use different threads in the tank.
Before I realized my new tank was different, I found the green seals on ebay. But I ended up have to get replacement pipes off ebay, as I recall.
So first check if your old pipes will even fit your new tank. If they don't, get different pipes. If you need the green seals, since you are in the UK, I'd talk to Ben at Simply Performance.
Here is another thread on the same subject.
https://www.jaguarforums.com/forum/x...-seals-261239/

Jon

 

I just found this on Google. Scroll down for the seals.
https://www.jagbits.com/category/XJS_FuelDeliv_4.html

 

I used viton tubing cut to length sourced from the link below. Works great, no fuel smell or leaks. I believe the same material as the original except not hardened after 30+ years. Not sure about your options to source over there but might give a starting point.

https://www.mcmaster.com/5119K91/

 

I'll see what Ben has to say and whether the hoses I have fit - this project never stops giving.

I have had a quick look and my sourcing options don't seem great - but since my pipes are of the 'olive' type if this tank is also of the olive type then why would these things be there ?? ....