Air Injection System: Operation: XJ12
The air pump supplies air under pressure through a diverter valve, check valve and air rails to the exhaust ports just above exhaust valve heads. The air combines with exhaust gases to further the burning process. Check valve prevents flow in air rails when exhaust pressure exceeds air supply pressure.
Diverter valve operates in response to abrupt fall in manifold pressure 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 backfire. The diverter valve is actuated by manifold pressure via a rubber tube connected to intake manifold.