I have a problem with the fuel evap system on my 1997 X100.
When the tank cap is removed theres a vacuum rush back into the tank. Even after just a few minutes on idle.
I've tested everything I can actually see like:
Control valve on the inner wing.
Rochester valve and pipework inside the left wheel arch liner.
Blown all the pipes to the rear to the tank. And it all comes out good. I've also run the engine and removed the vac pipe from the control valve on the inner wing and to be honest, there is some vacuum there but I was hoping it might have had more than it has. There is no fuel inside the plastic vac tank either.
Has anyone got any ideas? What usualy breaks down? Thanks.

 

Diagram of the 1997 XK EVAP system. It is basically the same as the 1997 sedan.

 

Maybe its the canister close valve or the free air pipe connected to it? Wasnt it a recall on those from Jaguar on the earlier models?

 

Are you sure it's not pressure in the tank escaping, rather than air rushing in to fill a vacuum?

 

Air rushing in seems more likely (and safer!)

 

Air rushing out is more common. Fuel evaporates and the fumes expand. Old school cars just vented it to atmosphere and if your gas cap's vent wasn't functioning you'd get a rush of air/fumes when you'd remove the cap. If the evap system isn't working the tank won't get vented and fume pressure can build.

 

Yeah, I always get a release of pressure when I open the cap, hence my question.