Evaporative Emissions System: Operation

Fuel vapors pass through the carbon canister and deposit hydrocarbons on the surface of the carbon. When the engine is running, fresh air entering the canister through an opening cleans the carbon and routes the hydrocarbons via the air cleaner back to the engine where they are burned during normal combustion.

On water cooled engines, any oversupply of fuel by the fuel pump is recirculated to the fuel tank via a fuel return line, to control fuel supply during engine idle. On air cooled engines, fresh air is blown through charcoal canister from blower housing to aid in purging action. This keeps emissions during idle at the required low level.