Anti-AFTERBURN Valve: Operation

The anti-afterburn valve is sensitive only to sudden increases in vacuum; the length of time it stays open is controlled by a diaphragm that senses change in manifold vacuum.

When manifold vacuum suddenly increases, as during sudden deceleration, the diaphragm/valve unit is pulled downward. Air flow from the air chamber to the sensing chamber is restricted by an orifice, creating a pressure differential on the diaphragm, which holds the valve open. This unbalanced condition lasts for a few seconds until the pressure in both chambers is equalized by air entering through the orifice, then the spring pushes the diaphragm up, closing the valve.