Air Injection: Description and Operation

Fig. 2, Air injection, EGR, and Fuel Evaporation system.:

The air injection system, Fig. 2, works to reduce exhaust emissions by introducing extra air into the exhaust stream. This extra air continues the combustion of the unburned fuel in the exhaust which reduces the HC and CO content before it reaches the catalytic converter. The extra heat generated by this burning also helps the converter get up to operating temperature faster.
Air injection occurs for a maximum of one minute when the coolant temperature is above 63°F (17°C), the engine is below 2500 rpm, the full load contact is not engaged and/or lambda control is operating.
Under these conditions, the control unit energizes an electro-magnetic clutch on the air pump by way of an air injection relay (located in the relay box next to the brake master cylinder). Simultaneously, the same relay energizes a switchover valve which provides vacuum to the air injection shutoff valve. The air pump draws air from the air filter and delivers it to the exhaust ports in the cylinder heads.