Fuel Control
The EFC system consists of fuel control system, electronic throttle control system, spark control system, data sensors, Spark Control Computer (SCC), electronic exhaust gas recirculation (EGR), electronic air switching and catalytic converter.
All models are equipped with feedback carburetors which contain an +electronically-operated duty cycle solenoid. This solenoid meters the main fuel system of the carburetor and operates in parallel with the conventional fixed main metering jets. The computer controls the operation of the solenoid with electrical signals, in response to input from data sensors. See Fig 1 or Fig 2 .
When the solenoid is de-energized by the computer, the solenoid valve spring pushes upward through main system fuel valve. When de-energized, the solenoid main metering orifice is fully uncovered, providing the richest mixture for any given airflow.
When the solenoid is energized by the computer, the solenoid main metering orifice is fully sealed. This solenoid position offers the leanest mixture within the carburetor for any given airflow.
Main system fuel may be regulated between richest and leanest mixture conditions by controlling the amount of time that the solenoid is energized and de-energized. The computer controls the duration of time that solenoid is energized in comparison to total time of solenoid operation.
This duration of time is determined by engine operating conditions and/or oxygen sensor signals. In this manner, the ideal air/fuel ratio can be constantly maintained.