Ran into this problem at the shop this week. Try this, there will be a sensor on too of the canister that has 3 wires it's the fuel pressure sensor. Tap into the light green wire and monitor fuel tank pressure. With the key on and gas cap off it should have 2.5v, put the cap back on and start the car. The pressure should rise too 2.8 to 2.9v then shut the car off with key on. The pressure should stay steady for a while and not drop instantly. If it drops instant then you have a leak, start checking all line, rubber hoses, filler neck, fuel pump ect. Mine turned out too have a bad 2 way valve and the canister was flooded with gas lol. Lmk if you have any questions.
thanks for this! will try this upcoming week!