Sucking Air

Hi Folks,
Recently got myself a V8i 1998 Disco. On recent expeditions to the petrol station, (which have been many) when unscrewing the filler cap there seems to be a great inrush of air.
Is this something to do with the pressurised fuel injection system? Should I be worried and is there anything I can do about it??

HI
I would say there is something wrong with the compensation ventilation hole, air does not seem to be able to replace the fuel used.

Ray

Have you got the correct fuel cap for the car, most modern caps have a breather valve in to prevent pressurisation.

Same as the above answers. Drill a small hole through cap to allow air in.Remove cap from vehicle before doing this and make sure you get rid of the swarf from the drilling process.

isnt the fuel system supposed to be presurised,or does the system presureise after the fuel pump

Think I might have found the problem. It has been suggested that the problem it might not be sucking as pressure coming out from the tank. Something to do with a bleed to the carbon filter as these days owing to Elf & safety you are not supposed to vent petrol vapour into the atmosphere??
The carbon absorbs this, then when the engine starts the vapour is purged by warm air pushing back into the combustion chamber. Does this make sense??

hi have the same problem when i undo the petrol cap if you solve the problem let me know what it is thanks