Roadmaster 1992

Air Injection Reactor System

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Air Pump



Location


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Fig. AIR pump location-1991-1993

Operation

The AIR management system, is used to provide additional oxygen to continue the combustion process after the exhaust gases leave the combustion chamber. Air is injected into either the exhaust port(s), the exhaust manifold(s) or the catalytic converter by an engine driven air pump. The system is in operation at all times and will bypass air only momentarily during deceleration and at high speeds. The bypass function is performed by the Air Control Valve, while the check valve protects the air pump by preventing any backflow of exhaust gases.

The AIR system helps reduce HC and CO content in the exhaust gases by injecting air into the exhaust ports during cold engine operation. This air injection also helps the catalytic converter to reach the proper temperature quicker during warmup.

The AIR system utilizes the following components:

  1. An engine driven AIR pump.
  2.  
  3. AIR Control valves (Air Control, Air Switching).
  4.  
  5. Air flow and control hoses.
  6.  
  7. Check valves.
  8.  
  9. A dual-bed, three-way catalytic converter.
  10.  

The belt driven, vane-type air pump is located at the front of the engine and supplies clean air to the AIR system for purposes already stated. When the engine is cold, the ECM energizes an AIR control solenoid. This allows air to flow to the AIR switching valve. The AIR switching valve is then energized to direct air to the exhaust ports.

If the AIR control valve detects a rapid increase in manifold vacuum (deceleration), certain operating modes (wide open throttle, etc.) or if the ECM self-diagnostic system detects any problem in the system, air is diverted to the air cleaner or directly into the atmosphere.

The primary purpose of the ECM's divert mode is to prevent backfiring. Throttle closure at the beginning of deceleration will temporarily create air/fuel mixtures which are too rich to burn completely. These mixtures become burnable when they reach the exhaust if combined with the injection air. The next firing of the engine will ignite this mixture causing an exhaust backfire. Momentary diverting of the injection air from the exhaust prevents this.

The AIR system check valves and hoses should be checked periodically for any leaks, cracks or deterioration.

Removal & Installation
  1. Before servicing the vehicle, refer to the Precautions Section.
    NOTE
    Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on-board computer systems and may require the computer to undergo a relearning process, once the negative battery cable is reconnected.


    NOTE
    If working near and/or around the SRS system and components, be sure to properly disable the SRS system. See disarming/arming the SRS system.

  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the AIR control valves and/or adapter at the pump.
  6.  
  7. Hold the pump pulley from turning and loosen the pulley bolts. Lift the belt drive tensioner to the raised position remove the pump and pulley assembly.
  8.  
  9. Unscrew the pump mounting bolts and then remove the pump pulley.
  10.  
  11. Unscrew the pump mounting bolts and then remove the pump.

    Click image to see an enlarged view

    Fig. AIR pump and related components-1991-1993



    Click image to see an enlarged view

    Fig. AIR injection tube locations-1991-1993

  12.  

To install:


NOTE
Be sure to use new fasteners, as required.


NOTE
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread sealer are identified. Do not use paints, lubricants or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners.

  1. Position the pump into place and secure it with the mounting bolts.
  2.  
  3. Install the pump pulley.
  4.  
  5. Install the air pump drive belt and adjust pump belt with the pump adjustment bolt, as required.
  6.  
  7. Install the AIR control valves and/or adapter.
  8.  
  9. Using the GM diagnostic scan tool or aftermarket equivalent reprogram the necessary systems and components. Be sure to follow the scan tool manufacturer-s directions.
  10.  

Testing


Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

 
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