Evaporative Emissions System: Description

An early fuel evaporation (EFE) system is used on all Light Duty and some Heavy Duty emissions models. System provides improved cold driveability while reducing exhaust emissions.

Fig 1: Early Fuel Evaporation System 6-Cylinder Engines

Courtesy of GENERAL MOTORS COMPANY

Fig 2: Early Fuel Evaporation System 5.0L & 5.7L V8 Engines

Courtesy of GENERAL MOTORS COMPANY

Fig 3: Early Fuel Evaporation System 7.4L V8 Engines

Courtesy of GENERAL MOTORS COMPANY

System consists of an EFE valve, an actuator and a thermal vacuum switch (TVS). The TVS is coolant temperature controlled on V8 engines and oil temperature controlled on 6-cylinder engines.