wierd problem

[gsxr141]

i have a strange issue regarding my gas tank. sometimes when i remove the gas cap, there's excessive pressure coming OUT. i know that sometimes there can be some vacuum, but i've never heard of positive pressure.
if anyone knows what might cause this, please let me know.
thanks............kevin

 

[mirage83]

There's usually a slight amount of pressure in the tank, iirc about 1 to 2 lbs, to assist the pump. Shouldn't be anything to worry about so long as the cap isn't being blown off. If you've got vacuum then I think it would indicate a problem with the fuel system (charcoal cannister?).

 

[bioskyline]

thats normal. hence why most caps say remove slowly.