[wraprail]

Wow I never heard of that. You should not have any raw/liquid fuel in the canister or the line running to it from the tank.
Have you replaced any of the hoses near the tank recently?
Maybe they got the vent and canister lines crossed. (I don't know if even this would cause your problem)
I just can't see how fuel could be sucked into the canister.
Should only be vapor.

Sorry I can't be of any help. I am curious as to the cause.

If you were from Okelaoma I might have an answer......
But I see you are from Cali Smog Pump Land..