Mixture Control Solenoid: Description and Operation

Duty Cycle:

The "Mixture Control" solenoid is located in the carburetor. This device helps regulate the air/fuel ratio by metering in additional fuel when the ECM senses a lean condition, and restricting fuel flow during rich periods. The ECM sends a voltage signal which turns the solenoid "ON" and "OFF" twice each second. Fuel metering is determined by the "duty cycle" ("ON" time vs. "OFF" time). When the solenoid is energized, fuel is restricted, therefor, a duty cycle of 90% (90% "ON" time vs. 10% "OFF" time, per cycle) represents a lean command (rich exhaust condition), and a duty cycle of 10% represents a rich command (lean exhaust condition.)