Exhaust Emissions System - Air Injection System: Operation: Notes

Air from the belt-driven air pump is injected into the exhaust ports near each exhaust valve. The oxygen in the air and the heat of the exhaust gas during the exhaust stroke induce combustion in each exhaust port, burning the excess hydrocarbon (HC) and carbon monoxide (CO) gases.

Normally, air flows from the pump through the check valve to the exhaust manifold, except when manifold vacuum is below the preset value of the vacuum switch (at heavy load) after a certain amount of delay time by the delay valve. The choke switch shuts off the by-pass solenoid valve during choke operation by interrupting the ground circuit. When either of the preceding conditions is present, air from the pump is routed back into the air cleaner assembly.