AMC Coupes/Sedans/Wagons 1975-1988 Repair Information

Air Injection System

Imprimir

DESCRIPTION



The exhaust emission air injection system consists of a belt driven air pump which directs compressed air through connecting hoses to a steel distribution manifold into stainless steel injection tubes in the exhaust port adjacent to each exhaust valve. The air, with its normal oxygen content, reacts with the hot, but incompletely burned exhaust gases and permits further combustion in the exhaust port or manifold.

Air Pump See Figures 1, 2 and 3

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Fig. Fig. 1: Exploded view of the air pump mounting4-150 engine



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Fig. Fig. 2: Common air pump system used on all models except 8-cylinder engines



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Fig. Fig. 3: Exploded view of the air injection system components used on 8-cylinder engines

The air injection pump is a positive displacement vane type which is permanently lubricated and requires little periodic maintenance. The only serviceable parts on the air pump are the filter, exhaust tube, and relief valve. The relief valve relieves the air flow when the pump pressure reaches a preset level. This occurs at high engine rpm. This serves to prevent damage to the pump and to limit maximum exhaust manifold temperatures.

Pump Air Filter

The air filter attached to the pump is a replaceable element type. The filter should be replaced every 12,000 miles under normal conditions and sooner under off-road use. Some models draw their air supply through the carburetor air filter.

Air Delivery Manifold See Figure 4

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Fig. Fig. 4: Location of the air diverter valve and manifold4-150 engine

The air delivery manifold distributes the air from the pump to each of the air delivery tubes in a uniform manner. A check valve is integral with the air delivery manifold. Its function is to prevent the reverse flow of exhaust gases to the pump should the pump fail. This reverse flow would damage the air pump and connecting hose.

Air Injection Tubes

The air injection tubes are inserted into the exhaust ports. The tubes project into the exhaust ports, directing air into the vicinity of the exhaust valve.

Anti-Backfire Valve

The anti-backfire diverter valve prevents engine backfire by briefly interrupting the air being injected into the exhaust manifold during periods of deceleration or rapid throttle closure. The valve opens when a sudden increase in manifold vacuum overcomes the diaphragm spring tension. With the valve in the open position, the air flow from the air pump is directed to the atmosphere.

On the 1972 6-232 engine, the anti-backfire valve is what is commonly called a gulp valve. During rapid deceleration the valve is opened by the sudden high vacuum condition in the intake manifold and gulps air into the intake manifold.

Both of these valves prevent backfiring in the exhaust manifold. Both valves also prevent an over right fuel mixture from being burned in the exhaust manifold, which would cause backfiring and possible damage to the engine.

REMOVAL & INSTALLATION



Air Pump

WARNING
Never place the pump is a vise or attempt to dismantle it. The pump has no internal parts that are replaceable and it is serviced as a unit. Never pry or hammer on the pump housing.

  1. Loosen the bolts on the pump pulley.
  2.  
  3. Loosen the air pump attachment racket. On V8 models with air conditioning, loosen the power steering pump to aid in drive belt removal.
  4.  
  5. Detach the air supply hoses at the pump.
  6.  
  7. Remove the drivebelt and pulley from the hub.
  8.  
  9. Unfasten the bolts on the bracket and remove the pump.
  10.  

To install:
  1. Place the pump on its mounting bracket and install, but so not tighten the attachment volts.
  2.  
  3. With the rotor shaft used as a center, fit the pulley into the hub and install the drive belt over the pulley.
  4.  
  5. Tighten the pulley attachment bolts, using care not to snap them off.
  6.  
  7. Adjust the pump until the belt is secure. Tighten the mounting bolts and the adjusting screw to 18-22 ft. lbs. Do not overtighten.
  8.  
  9. Attach the hoses and clamps.
  10.  

Air Pump Relief Valve

  1. Use a gear pulley and a steel bridge to remove the relief valve from the pump.
  2.  
  3. Remove the pressure plug from the new relief valve assembly.
  4.  
  5. Insert the relief valve into it housing mounting hole.
  6.  
  7. Place a block of wood over the valve. Use a hammer to tap the valve until it lightly registers against the housing. Use care not to distort the housing.
  8.  
  9. Press the pressure plug into the center of the relief valve.
  10.  

Centrifugal Filter Fan

Never attempt to clean the filter fan. It is impossible to remove the fan without destroying it.

  1. Remove the air pump from the car, as detailed above.
  2.  
  3. Gently pry the outer disc off and pull off the remaining portion. Be careful that no fragments from the fan enter the pump air intake.
  4.  

To install:
  1. Install a new filter fan pulling it into place with the pump pulley and attaching bolts.
  2.  
  3. Alternately tighten the bolts so that the fan is drawn down evenly. Be sure that the outer edge of the fan fits into the pump housing.
  4.  


WARNING
Never hammer or press the fan into place; damage to it and the pump will result.

  1. Install the pump on the car.
  2.  

For the first 20-30 minutes of operation, the fan may squeal until its lip has worn in. This is normal and does not indicate a damaged pump.

Exhaust Tube

  1. Remove the exhaust tube by grasping it (never the pump body) in a vise or a pair of pliers. Pull the tube out with a gentle twisting motion.
  2.  
  3. Install the new exhaust tube by tapping it into the hole with a hammer and a wooden block. Be careful not to damage its end.
  4.  
  5. Tap it until 7 / 8 in. (22.23mm) of the tube remains above the pump cover.
  6.  

Do not clamp the pump in a vise while installing the exhaust tube.

By-Pass (Diverter Valve)

  1. Disconnect the hoses from the valve.
  2.  
  3. Remove the screws that attach the valve bracket to the engine. Remove the valve and bracket assembly.
  4.  
  5. Installation is the reverse of removal.
  6.  

Air Injection Manifold and Check Valve Assembly

6-232 AND 258 ENGINES
  1. Remove the intake/exhaust manifold assembly, after disconnecting the hoses from the air injection manifold.
  2.  
  3. Place the assembly in a vise and unfasten the retaining nuts on the air injection manifold at each cylinder exhaust port.
  4.  
  5. Lightly tap the injection tubes, then pull the injection manifo