Originally Posted by keninsb
THAT is what I was thinking of. Seems kind of lame that they even bother with the charcoal canister. I used to work at a company called "Vetronix" (since purchased by Bosche) that made the scan-tools for Toyota, Lexus, Nissan, Acura, GM and other manufacturers) and we had a guy that was an ex-Master Mechanic. Anyway, we were talking about the charcoal canister and it seems to be a waste, like a "1-shot deal". If you overfill the tank ONE time, it ruins the charcoal (it can only absorb so much of anything). guess it is the last leg of the coal industry (thanks mr. president).
The purpose of the canister is not to absorb excess fuel. It is not an overflow pipe, and the canister is not there to capture "overflow" fuel.
The canister is working constantly. Like the screen in the air filter
housing, it captures fuel vapors exiting the tank vent and prevents them from being released into the atmosphere.
When the engine is started, the ECU opens the purge valve and air is drawn into the intake manifold through the canister. This pulls the captured vapors into the engine.
If your fuel cap is not installed properly, you will get a CEL with a Evap system code... the system is a "closed" system, but since the tank can not be completely sealed unless it were a bladder, the charcoal canister is the filter isolating the fuel in the tank from the outside air.
And activated charcoal is not coal... it has nothing to do with the coal industry. It is more closely related to what you stoke your BBQ with.