Evaporative Emission Control Canister: Description and Operation

EVAP Canister Operation:

PURPOSE
Prevents fuel system damage, by venting the system in the event of high internal pressure or vacuum.

Prevents fuel and vapors from escaping into the atmosphere, (except under extreme conditions, see above).


OPERATION
Under certain conditions, fuel and fuel vapors in the fuel tank expand.

When the volume of the tank is exceded, by vapors or fuel and vapors, the overflow is routed, through the pressure relief/rollover valve, to the EVAP canister nipple labeled "Fuel Tank".

The vapors are absorbed by the carbon in the canister, and any liquid fuel enters the reservoir in the bottom of the canister, (to protect the carbon bed above).

The fuel and vapors are stored in the canister, until the engine is started and certain conditions are met.