Vented gas cap?

gm1236 said

One thing I don’t quite understand, the vented cap will release pressure and let it out, the evap system also absorbs the escaping fumes. I’m looking to allow air into the tank, it has to get in so the fuel can get out. Does the evap system allow for this? If not what does? This simple tube vent system will.
Do you need to plug the tube when the car is stored inside?

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The caps on all the evap control years are only for "last ditch" pressure/ vacuum release, that is, tank pressure builds up they "pop off." The actual vent was done via the 1/4" tube going up front to the evap system.

So the cap pops off pressure in either direction, and the tube up front is also bi-directional, forcing fumes into the evap system, and allowing air back into the tank