Fuel Evaporation System: Operation
Fuel vapors, formed in fuel tank, are collected in liquid-vapor separator tank. Liquid fuel and condensate formed in tank are returned to fuel tank by way of a hose connected to bottom of liquid-vapor separator. Fuel vapors flow through connecting hose and enter engine at cam covers.
When engine is not running, vapors are stored in crankcase of engine. When engine is running, vapors are purged from crankcase by crankcase ventilation system and are burned in the engine. Fuel tank cap is air tight to prevent fumes from escaping into the atmosphere.
If temperatures should decrease after engine shutdown, a vacuum would tend to form in fuel tank and liquid-vapor separator tank. Should this happen, fuel vapors would flow back into system from crankcase and maintain system at atmospheric pressure. Should the vapor line between the separator tank and camshaft cover become plugged, the vacuum relief valve will open to prevent a vacuum from forming in the system.