So before you freak out that i cut up a part that is unobtainable, this one was bad. I've looked around before trying to find a dissected pic of one of these and never had much luck. So I thought I'd share.
So first pic is from the bottom looking up at where the ports come in at.
Second pic gives you a better orientation of the first pic.
The roundish foam pieces in the second pic sat in the bottom of the canister on top of the grate. this is what keep the charcoal inside.
Yes. Tank vents to inner circle and vents from outer circle. Hydrocarbons heavier than air and fall to bottom. Then vent out up through charcoal. And, if your vacuum valve is bad and passes air all the time, you can plug the signal hole on it with a screw and add a new external vacuum valve for about $9.