2nd Gen Non-Engine/Transmission fuel tank pressure??

[stevegeorge]

have a 99 CTD. Everytime I open the fuel cap, there is either a vaccuum or pressure (don't know which) hiss. I have checked for the proverbial cap left on the vent tube on top of the tank, but it was not there. Is this normal?

 

[illflem]

The cap releases pressure at 2. 5 psi and vacuum at -. 29 psi. There should be a little hiss, but not enough pressure to bloat or collapse your tank.