Early Fuel Evaporation System: Description
Two Early Fuel Evaporation (EFE) systems are used on General Motors light and heavy duty trucks. EFE systems are used to provide heat to engine induction system during cold driveaway. Engines may be equipped with either electric heater type (4-cylinder and V6) or vacuum operated exhaust heat riser valve type (all others) EFE system.
Both electric and vacuum type systems provide rapid heating, resulting in faster fuel evaporation and more uniform fuel distribution. This also helps reduce choke "ON" time by warming engine faster.