there are several reasons why a 440 code will appear other than a gas filler line leaking. First, fix the leak in the gas filler line and clear the code. If it returns there are other possible causes, a faulty fuel filler cap, faulty purge solenoid or a blocked or malfunctioning Evap canister. Check for any cracks in the evap lines and if all else fails, have a professional do a smoke check to find the "hard to find" leak.
