Fuel Evaporation System: Operation
When engine is stopped, fuel vapor from fuel tank flows through vapor line into charcoal canister where it is stored. When engine is running, fresh air is drawn through charcoal canister as manifold vacuum pulls stored fuel vapor into combustion chambers for burning. The check valve regulates the amount of vapor flow.
A rollover valve in the fuel evaporation line shuts off line if vehicle turns over. It is located in-line, above fuel tank. The vacuum relief fuel filler cap lets air into the tank if the vent lines become plugged. This prevents tank collapse or engine fuel starvation.