Vacuum Throttle Positioner: Operation

The electronic speed switch receives an ignition pulse through the ballast resistor, which is connected to the electronic ignition control unit. It then senses when engine speed is above 2, 000 RPM and energizes the throttle positioner. By energizing, the throttle positioner plunger extends slightly and will hold the throttle blades open at 1750 RPM upon sudden deceleration. This will prevent an overly rich mixture from flowing into the carburetor.

When the speed switch senses that engine RPM has dropped below 2000 RPM, it de-energizes the positioner and throttle blades are allowed to return to normal idle position.