evap purge solenoid help

[jrs86]

i dont have my chilton with me so i need a lil help understanding when during engine operation does the purge valve open. i went to get a smog and they told me all was good but it failed the evap test so after 5 min or so i found the fuel filler hose was cracked and even leaking fuel. problem solved right but now the fuel cap is purging the vapors. i have no codes and i want to make sure all is right before i take it again