I cut open a gas tank and EVAP canister to see what’s inside and how it works. I made a short video on the process, you can check it out here: Here are a few photos of the teardown: The EVAP canister is located behind the gas tank: The gas tank is held on by two straps. Boy was there a lot of rust on this Corolla! Down comes the tank: One bolt for the filler neck: Gas tank, EVAP canister removed: Here’s what some of those vacuum lines do: Vacuum lines on the gas tank: Here’s an overview of the EVAP system. Its basically there to vent gasoline vapors and catch it in the charcoal canister. Its held there until its released into the car’s air intake to get burned by the engine. EVAP float to ensure liquid gas doesn’t go into the charcoal canister: Here’s the gas tank chopped open: Vapour pressure sensor. ECU uses this for self-diagnostics. That’s why it’s so difficult to pass emissions tests! Fill check valve. This controls the ventilation of the gas tank while refueling. Its pretty cool inside, there’s a diaphragm that works with air pressure. It allows vapor to move in one direction only Chopping open the charcoal canister: Tiny beads of activated charcoal: Which gives me an idea…Barbeque anyone?