Air Injection System: Operation: XJS
The air pump supplies air under pressure through a diverter valve, check valve, and air rails to the exhaust ports just above exhaust valves. The air combines with exhaust gases to further the burning of hydrocarbons. Check valve prevents flow into air rails when exhaust pressure exceeds air supply pressure.
Diverter valve operates in response to abrupt increase in manifold vacuum and diverts secondary air to atmosphere for 2-3 seconds. This reduces air/fuel ratio which otherwise would be too rich to burn and would pass through engine to mix with secondary air and become combustible, creating a backfire.