Evaporative Emissions System: Operation
Expanded fuel caused by high temperatures is collected in expansion chamber of fuel tank. Fuel is returned to main tank by venting action as fuel is used from main tank. When engine is stopped, fuel vapors 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.
When engine is at idle, fuel vapors flow from the charcoal canister through a restrictor to the intake manifold to be burned. A safety valve, located between charcoal canister and fuel tank, closes to prevent fuel leakage if vehicle turns over.
An on/off valve, located between charcoal canister and air cleaner, reduces hydrocarbon emissions by closing at idle to prevent vaporized fuel from entering air cleaner. Throttle housing vacuum opens valve as engine speed increases.