my car is hard to start after i put gas in it

What is your question?

When i put gas in my car it is hard to start like its not getting gas it will start to idel really bad but it will start i replaced the gas cap no different the engine light is on i got it checked on a computer it said vapor leak any ideas where to start after I get it started it is fine again until i put gas in it again. the part store told me i do not have a fuel filter in my car.