EVAP and how it works

[shizon]

Can anyone explain how the pcm uses the fuel tank pressure sensor to control the purge/vent valves in the EVAP canister and when it does it's leak test and how? I think we're having a tank venting problem and I want to know if it's during the leak test.

Lots I don't understand here...

BTW, the car is an 04 GTO. The car has a sumped tank, but all stock bucket, pump, and evap stuff is in place.

[EC_Tune]

Fuel tank pressure is mostly used during engine off operation. The purge system seals up and the tank pressure is monitored. If the pressure doesn't rise enough over a specific time period based on fuel level, the evap system is considered "leaking" and a code will be set.