System Components

Fig. 2 Typical AIR manifold and injection nozzle installation:

AIR systems include a belt driven pump, vacuum operated flow control valves, delivery hoses, check valves and manifolds, and injection nozzles, Fig. 2. A deceleration valve, used on some 1983-86 6 and V8 cylinder engines, and the mixture control valve used on 4-119 engines, is also considered part of the AIR system.

Fig. 3 Air control valve (AC) operation:

AIR FLOW CONTROL VALVES

Air Control Valve (ACV)
Air injection on 4-119 federal engines is controlled by a vacuum operated air control valve, Fig. 3. When manifold vacuum is above a specified level, the vacuum pressure holds the ACV open and air pump output is directed into the exhaust stream. When manifold vacuum drops below the calibration point of the ACV, spring tension closes the air injection port and air pump output is directed to atmosphere.

Fig. 4 Diverter valve (DV) cross-sectional view:

Diverter Valve (DV)
Air injection on all except 4-119 engines is controlled by the diverter valve, Fig. 4. During normal running, the diverter valve is open and air pump output is directed into the exhaust stream. During deceleration, high manifold vacuum is applied to the diverter valve diaphragm, and air pump output is vented to atmosphere until the vacuum signal bleeds-off through a timing valve. An integral pressure relief valve prevents excessive system pressures during high RPM operation.

Fig. 5 Air Pump. 4-119 engines:

Fig. 6 Air Pump. Except. 4-119 engines:

AIR PUMP
The air pump is a positive displacement, vane type compressor. Air pumps are permanently lubricated and do not require periodic maintenance. The air pump used on 4-119 engines, Fig. 5, contains an integral pressure relief valve, but does not have a provision for filtering intake air. The pump used on all other engines, Fig. 6, is equipped with a centrifugal filter mounted behind the drive pulley, but the pressure relief valve on these models is located in the diverter valve. Both pumps are driven by the engine through a V-type belt and draw fresh air through the engine air cleaner.

Fig. 7 Check valve cross-sectional view:

CHECK VALVES
The check valves are designed to only allow air flow in one direction, Fig. 7. The valve is opened when air pump pressure overcomes spring tension, and is closed when the combination of spring tension and exhaust back pressure exceeds air pump pressure. Check valves are mounted on the injection manifolds with a threaded fitting and connected to air flow control valve by hoses.

Fig. 8 Mixture control valve (DEC-MC) operation:

DECELERATION & MIXTURE CONTROL VALVES
The Mixture Control Valve used on 4-119 engines or Deceleration Valve used on other engines, allows filtered air to enter the intake manifold during deceleration in order to prevent backfiring by ``leaning-out'' the air/fuel mixtures. During normal operation, the valves, Fig. 8, are closed preventing air from entering the manifold directly. During deceleration, high manifold vacuum is applied to the valve diaphragms and air enters the intake manifold. The valves will continue to supply air to the manifold until the vacuum signal falls below a specific value.

Fig. 2 Typical AIR manifold and injection nozzle installation:

HOSES, MANIFOLDS & NOZZLES
Air pump output is fed through hoses and check valves into an air manifold where it is distributed to injection nozzles. The nozzles are positioned near the exhaust valves and pointed toward each valve, Fig. 2. Manifold installation and hose routing varies depending upon application.