Early Fuel Evaporation ( EFE ): Description and Operation

Fig. 34 Typical early fuel evaporation system:

The electric EFE system, Fig. 34, incorporates a ceramic heater grid located beneath the primary bore of the carburetor as part of the carburetor insulator gasket. Its purpose is to heat the incoming fuel/air mixture for improved vaporization and driveability during cold engine operation.

When ignition switch is turned on, voltage is applied to a thermo switch. If coolant temperature is below a specific value, the thermo switch is on and a circuit is completed to the heater and current flows. The heater, through a positive temperature coefficient (PTC) semi-conductor element, increases in temperature to a predetermined level except at high engine speeds when fuel/air flow will reduce temperature below this level. When coolant temperature reaches a specific value, it shuts off thermo switch and cuts off current to heater.