Sorry if this has been addressed, but I couldn't find it..... anyway, I have a 1994 XJS V-12 6.0 L. When I fill the tank, then drive, gas leaks out onto the paintwork. Once the level gets lower, it stops. The filler cap and the entire mechanism is almost new and the O-ring around the base is new. The springs pushing the seal down onto the opening when closing the cap are strong and the rubber bit that seals the opening looks new. Any help?
Thanks,
Bill

 

Hi drbill

Have you checked the 'Breather Pipe' it could be coming out of there, or if its blocked could then cause pressure in the Tank to force Gas past the Filler Cap seal, even if it is in good condition

 

When the pump clicks off stop there don't try to top off. Mine leaks from somewhere under if I try to top off.