Single Air Pump

Air Injection System:

SYSTEM OPERATION

The air injection system is composed of a belt-driven air pump, an air control valve (diverter valve, switch/relief valve), rubber hoses, check valves to protect the hoses, and injection tubes. This system adds a controlled amount of air to the exhaust gases aiding the reduction of hydrocarbons and carbon monoxide in the exhaust stream.

Air passes through a plastic centrifugal filter fan at the front of the air pump, and foreign materials are filtered out of the air by centrifugal force. Air is then injected at the exhaust ports for a short time during engine warm-up. The air flow is then switched to a point downstream where it will assist the oxidation process in the catalyst but not interfere with exhaust gas recirculation. The switching is controlled by an electronically controlled vacuum switch.


CHECK VALVE

The check valves are located in the injection tube assemblies. One upstream at the exhaust manifold, and the other one downstream at the catalyst injection point.

The purpose of the check valve is to protect the air injection system in the event that the air pump belt fails, exhaust system pressure raises to an abnormally high level, or an air hose ruptures. This valve has a one way diaphragm which prevents hot exhaust gases from getting to the rubber hoses or the air pump.

Air Switch/Relief Valve:

AIR SWITCH RELIEF VALVE

The switch/relief valve has two specific functions. First, it directs the air from the air pump to either the exhaust manifold, upstream, or to a location downstream, exhaust pipe or catalytic converter. Finally, the valve regulates the amount of output of the air pump at high speeds. When the output reaches a certain level (approximately 9 psi), some of the output is vented to the atmosphere.

This valve is controlled by manifold vacuum and a vacuum operated solenoid. During cold operation a vacuum signal is sent to the switch/relief valve, this directs the air pump output to the upstream location as close to the exhaust valves as possible. Once the engine warms up to normal operating temperature, then the vacuum operated solenoid allows the vacuum signal to bleed off to the atmosphere, thus shutting off the vacuum signal to the switch/relief valve. When there is no manifold vacuum signal to the valve, most of the air pump output is directed to the downstream location.

Solenoid Trio:

AIR SWITCH/RELIEF VALVE SOLENOID

The switch/relief valve solenoid is a vacuum operated solenoid that controls the operation of the switch/relief valve. The vacuum operated solenoid is part of a vacuum trio located on the right valve cover, towards the firewall.

Power Heat Control Valve:

POWER HEAT CONTROL VALVE

The power heat valve is located between the right exhaust manifold and exhaust pipe. It is a vacuum operated device which directs most of the exhaust flow to the left-hand exhaust manifold. This redirecting of exhaust helps to improve cold engine driveability, and also warms the oxygen sensor.

The power heat valve is controlled by an electronic solenoid. This solenoid controls the manifold vacuum signal which is used to activate the power heat valve. At coolant temperatures below a predetermined level, manifold vacuum is applied to the power heat valve and all exhaust flow is directed to the left-hand exhaust manifold. Once the coolant temperature rises above the predetermined level, then the solenoid closes off the vacuum signal and the power heat valve opens allowing exhaust to flow through both manifolds.

Diverter Valve:

DIVERTER VALVE (EXCEPT FEDERAL)

The diverter valve is located upstream of the switch/relief valve. It's purpose is to prevent backfire during deceleration. The diverter valve senses changes in manifold vacuum. When decelerating, vacuum increases rapidly. This increase causes the valve to open thus allowing air from the air pump to vent through the silencer and out to the atmosphere. When accelerating, vacuum drops rapidly. This decrease in vacuum causes the valve to shut allowing air to flow either upstream or downstream.
A pressure relief valve is also incorporated into the diverter valve. It's purpose is to allow excessive air pump output to be vented to the atmosphere under high system pressure conditions (approximately 9 psi), specifically high engine speeds.