Charcoal canisters

My Nissan has a charcoal canister and there are four pipes:

One coming from the petrol tank, I assume this is the 'vapours'.
One at the bottom going back under the car, I assume this is for liquid
petrol to drain back into the tank.

Two at the top, one connected to manifold vacuum and one ending up (via the
EGR valve) at a vacuum valve solenoid.

The valve opens and closes to activate the EGR and suck fumes from the
canister at the same time, by the look of the system.

So I can't suck or blow through either of the latter two. Is that normal? I
suspect not!


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