Mixture Control Solenoid: Description and Operation

Solenoid Valve Locations:

This valve is located in the carburetor float chamber cover

Solenoid Valve Duty Cycle:

The ECU controls the air-fuel ratio by controlling the duty cycle of the valve. The frequency of ON-OFF cycles remain constant at 10 Hz pulses, but the solenoid "ON" time portion of each cycle is changed to modify the duty ratio. The higher the duty ratio (the longer the ON time), the leaner the air-fuel ratio.

Feedback Solenoid Valve (FBSV) Control System:

When the FBSV is energized, the main fuel jet is closed, leaving the primary main jet passage as the only passage supplying fuel to the main circuit fuel nozzles in the carburetor venturi. This results in a lean air-fuel mixture. When the FBSV is de-energized, the main fuel jet is opened providing a second fuel passage to meter fuel. Since this will increase the amount of fuel already being supplied, a rich air-fuel mixture results. With the ON-OFF operation (duty cycle) of the FBSV, the air-fuel mixture is controlled. For a more detailed description, and for ECU diagnostic procedures refer to COMPUTERIZED ENGINE CONTROLS.