Early Fuel Evaporation ( EFE ): Description and Operation

The electric EFE device utilizes a ceramic heater located underneath the primary bore of the carburetor as part of the carburetor insulator gasket. It heats the incoming air-fuel mixture to improve vaporization and driveability on cold driveaway.
When the ignition switch is turned on, voltage is applied to an engine coolant temperature sensor and ECM. If engine coolant temperature is below the specified value, the heater is supplied electric current. The heater, incorporating a positive temperature coefficient (PTC) semiconductor element, increases in temperature and is then self-regulated at a specified temperature, except at high engine speeds when the fuel-air flow will reduce the temperature below the specified value. When the engine coolant temperature reaches the calibrated value [158 ± 9°F (70 ± 5°C)], the EFE relay ground is removed by the ECM which opens the relay and shuts off the current to the heater.