fuel leak from air pump for fuel system Diagnostics on 2005 BMW 325i

after engine is shut off and car sits a short time. fuel leaks from little black canister at right rear behind wheel what could it be? 60000 miles .I just bought it The BMW dealer can't find the problem they tried by replacing a air pump for diagnostics, gas still comes out of that pump Help!

Asked by for the 2005 BMW 325i
The black canister you describe sounds like a "charcoal canister". The charcoal canister is part of the emission control system and should only store gas vapor not "liquid gasoline". Liquid gas should not be entering the canister. Its hard to believe BMW can't figure out the problem. I would go back and complain.