Evaporative Emissions System: Operation

With engine off, fuel vapors from fuel tank flow through a vent line to charcoal canister, where they are stored. When engine is running above idle speed, intake vacuum draws fresh air through charcoal canister and pulls stored vapors into the intake system through the air cleaner.

An on/off valve, located between charcoal canister and air cleaner, reduces hydrocarbon (HC) emissions by closing at idle to prevent vaporized fuel from entering air cleaner. Throttle housing vacuum opens valve as engine speed increases. A safety valve, located between fuel tank and charcoal canister, closes to prevent fuel leakage if vehicle rolls over.