Evaporative/charcoal canister port blocked?

Hey, all.
I drive a 1999 Subaru Legacy Outback.
I had a cracked evap canister, so I went to the junkyard and grabbed another. I installed it, but had problems filling the gas tank. It would fill a few seconds, then shut off.
So, I got home, pulled the evap canister, and blew through each of the three ports. Two of them had air flow in and out to each other, the third was blocked.
Checking the ops diagram, looks like that port runs to the intake manifold.
Should it be blocked (has a check valve or something), or should it have airflow?
Thank you.

Try sucking on that port, like the intake manifold does…I would not use my lungs to do this…

Will your tank fill normally with the canister disconnected?

I don’t know for sure, though it very well may have a check valve in it that only allows things out of that port, but not in. So instead of blowing, try putting a little vacuum on it. That’s what the engine does when it purges.

If you want to be sure that the filling issue is directly connected to this canister, temporarily disconnect it and see what happens. If there’s no change then the trouble will be elsewhere.