Fuel Evaporation System: Operation

When engine is stopped, fuel vapors from fuel tank flow through vapor line into charcoal canister where they are stored. When engine is running, fresh air is drawn through charcoal canister as manifold vacuum pulls the stored fuel vapors into the combustion chambers for burning.

A rollover valve in the fuel evaporation line shuts off line if vehicle turns over. It is located in the line above fuel tank.

The pressure valve maintains a small pressure in the tank to prevent intermittent fuel pump cavitation or vapor lock when engine is running at high ambient temperatures and/or high altitudes.

The special filler cap contains a vacuum relief valve to let air into the tank if the vent lines become plugged. This prevents tank collapse or engine fuel starvation.