Air Injection Pump: Description and Operation

Engine Management System:

Secondary Air Injection
The Secondary Air Injection (AIR) Pump (21), on command from the ECM, via a relay, provides additional air to reduce the level of Carbon Monoxide (CO) and Hydrocarbons (HC), in the exhaust gases. The additional air accelerates the rise in exhaust temperature to rapidly reach the catalyst operating temperature level. When the relay energizes the pump in the AIR system it also energizes the solenoid controlling the integral stop valve, opening the air line, through the mechanical check valve (22), to the exhaust manifold.

Fig. 1 Air Pump:

Air Injection Pump Description
The electrical air pump is a regenerative turbine type which is permanently lubricated and requires no periodic maintenance. The pump draws air from the air cleaner and pumps it under pressure to the check valve mounted near the exhaust manifold; this check valve will prevent exhaust gas blowing back to the pump. Battery voltage to the AIR pump is supplied through the AIR pump relay which is controlled by the ECM. The pump has an integral, solenoid operated, stop valve which operates with the pump. When the pump is not operating the solenoid valve is at rest preventing air flow through the pump.

AIR pump operation is only possible when the coolant temperature is at or below 16 °C. The system will run for 15 seconds at engine start-up or until the coolant reaches 16 °C; the maximum pump running time is four minutes. The ECM checks the AIR system airflow using the electrical circuit and lambda feedback detecting additional air in the exhaust.

Updated Information, Air Injection Pump











A Saginaw electric pump replaces the Nippondenso engine driven pump. The air cutoff valve is deleted and the associated pipe- work is revised accordingly. The new air injection pump attaches to an engine bracket using rubber shock mounts. On the NA engines the new pump is located in the same position as the previous version, at the front left side of the engine. On the SC engine, the new pump is installed on the front right side of the engine.

The pump has a regenerative turbine coupled to a dc electric motor within a housing. An integral solenoid valve controls the flow of air from the pump. Two stub pipes on the rear of the pump are connected to the air intake and outlet hoses. An electrical connector on top of the pump provides the interface with the vehicle electrical system.

At engine start, the engine control module (ECM) energizes the air pump relay, and power is supplied to the pump motor and the solenoid valve. The solenoid valve opens and the pump supplies air to the exhaust manifolds, via the check valve. After 25 seconds the air pump relay de-energizes, closing the solenoid valve and stopping the pump