Evaporative Emissions System: Description

The Early Fuel Evaporation (EFE) system is used on many General Motors engines to provide extra heat to the engine induction system during cold driveaway. This extra heat provides quicker fuel evaporation and better fuel distribution. It also helps reduce the choke "on" time by helping warm up the engine faster. System consists of a vacuum-operated heat valve installed in the exhaust pipe, a vacuum actuator, a thermal vacuum switch and, on some engines, a check valve.