Early Fuel Evaporation ( EFE ): Description and Operation

Early Fuel Evaporative (EFE) System:

DESCRIPTION
The Early Fuel Evaporation (EFE) system provides a source of rapid heat to the air/fuel mixture during cold start conditions. Rapid heating provides quick fuel evaporation and more uniform fuel distribution to aid cold driveability conditions. The EFE system also reduces the length of time the engine is in open loop, reducing the exhaust emission levels. The EFE system consists of the EFE heater, located between the Throttle Body Fuel injection (TBI) unit and the intake manifold, and the Positive Temperature Coefficient (PTC) heater relay, is mounted in the relay box.

OPERATION
When the Engine Control Module (ECM) determines that the Engine Coolant Temperature (ECT) sensor is below operating temperature and the engine speed is above idle, it will energize the PTC heater relay coil. Voltage is supplied to the EFE heater through the PTC heater relay contacts. The EFE heater will preheat the air/fuel mixture before it enters the combustion chambers and as a result, the fuel is atomized more efficiently. When the engine reaches operating temperature, or the engine speed is reduced to idle, the ECM will de-energize the EFE system.