Abstract: An apparatus and method for use with a carbureted internal combustion engine that accurately controls the amount of fuel that passes through the carburetor into the combustion chamber of the engine. A controlled triggering system controls the activation and deactivation of a solenoid. The solenoid, in turn, operates a plunger that varies the flow of fuel during the fuel intake cycle of the engine depending on the amount of fuel needed by the engine under any operating load. Thus, an engine can run leaner under partial load and run richer during periods of load and acceleration. By controlling the air-to-fuel ratio lower engine emissions and fuel consumption can be achieved.

Abstract: An ion sensing arrangement for a small internal combustion engine includes an ion sensor placed in the engine's combustion chamber to measure the conductivity of the combusted fuel-air mixture. Scaling circuitry, such as variable voltage divider circuitry, is connected to be in electrical communication with an output of the ion sensor. The scaling circuitry operates to adjust the output signal to a value appropriate for measurement. Preferably, the scaling circuitry adjusts the output signal based on a comparison with a reference value.