Fuel Evaporation System: Operation
As fuel expands in tank, fuel laden vapor is forced out of tank through an upper vent port. Vapor flows up through a gravity valve and into an expansion tank where liquid fuel condenses and returns to fuel tank as temperature drops.
Fuel vapor then flows from an upper vent port on expansion tank, through a control valve, and into the charcoal canister where it is adsorbed until manifold vacuum pulls it out of canister for burning.
When the engine is running above idle, a vacuum signal opens control valve and canister vapor is drawn from canister through control valve and into intake manifold for burning.