1999 Audi A6 Gross Evap leak

Hi, I have a 1999 Audi A6 2.8 Quattro. I have a " gross evap leak" code coming up on the computer, along with two bad o2 sensors. When i get gas, after pumping, the car wont turn over right away. you have to just hold the key on and it turns over and over and over for up to maybe 10-15 seconds sometimes before it actually starts. i tested to see of the cap was bad by just seeing if it happens when i dont click it enough, i opened the cap when not getting gas, and then cclosed it and started right up. i also put gas in myself with a funnel and a 5 gallon can of gas, and it started right up. can some one please tell me what they think about this. your help is much appreciated!