2006 Mazda 3 4 cyl Front Wheel Drive Automatic 45,000 miles

Whenever I put gas in my car, it won't start. I have to rev up the engine over and over, and then hurry up and throw it in drive and take off before it dies again. It is fine any other time, only when I refuel it. The check engine light has been on, and when they hooked it up to that thing at autozone, he said it was on for my gas cap, but that wouldn't be causing the trouble i am having. So i don't know... Please help?!!