Early Fuel Evaporation System: Description
Two Early Fuel Evaporation (EFE) systems are used on light and heavy duty trucks. The EFE systems are used to provide heat to the engine induction system during cold driveaway. Engines may be equipped with either an electric heater type (4-cyl.) or a vacuum operated exhaust heat riser valve type (all others) EFE system.
Both the vacuum type and the electric type systems provide rapid heating, resulting in faster fuel evaporation and more uniform fuel distribution. This also helps reduce choke "on" time by warming the engine faster.