fuel leak 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
It sounds like you have a problem with your Evaporative System. I would take it back to who sold you the vehicle and it should be properly repaired for no charge. This is a dangerous fire hazard situation. It is not legal to sell an unsafe vehicle in any State by anyone. If the person, lot etc objects, tell them that you will be engaging an attorney to handle this ASAP.