Renault Coupes/Sedans/Wagons 1975-1985 Repair Guide

Air Injection Reaction System



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Fig. Fig. 1 Typical Air Injection Reaction (A.I.R.) system-LeCar shown, other models are similar

The Air Injection Reaction System (A.I.R.) Has been used on the Renault engines, equipped with carburetors, beginning with the 1973 models and fuel injected engines, beginning with the 1975 models.

This system acts upon the exhaust gases to aid in further combustion as the gases leave the combustion chambers. To accomplish this, compressed air is injected into the cylinder head, just downstream of the exhaust valves. The injection of oxygen in this air stream, plus the heat of the exhaust gases causes the combustion to take place in the exhaust manifold to lower the emissions of hydrocarbons and carbon monoxide into the atmosphere by the exhaust system.

The A.I.R. system consists of the following basic components.

  1. Air Pump -Air pump is a two vane rotary pump which draws air through filter. When engine speed increases, volume of air from pump also increases.
  3. Pressure Regulator Valve -Located on discharge line of pump and limits air pressure to a maximum of 4.27 psi at 3000 RPM.
  5. Air Shut Off Flap -Operated by choke cable. Flap prevents air from flowing to intake manifold when choke is in operation. With engine running and choke operational, air exits by pressure regulator valve.
  7. Air Control Valve -Located on top of anti-backfire valve. Valve remains closed at starting and idling. As engine speed increases, air pressure increases causing diaphragm to pull plunger upward. This allows air to enter intake manifold.
  9. Anti-Backfire Valve -Located under air control valve. Operated by vacuum from intake manifold, valve allows air to enter intake manifold upon deceleration. Additional air leans air/fuel ratio which reduces level of emissions during deceleration.
  11. One-Way Valve -Located on air manifold supply line. Valve prevents exhaust gases from flowing back into pump, causing damage to pump.
  13. Manifold & Air Injectors -Directs air in exhaust ports to exhaust valve heads.

1975 and later carbureted models have a diverter valve that cuts off the injection of air into the exhaust system when the catalytic converter exit temperature becomes excessively high (832°-90°F.) on automatic transmission equipped vehicles or on manual transmission equipped models when the catalytic converter exit temperature becomes excessively high (832°-90°F.) or during the time the engine oil temperature remains below 59°F.


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Fig. Fig. 2 Combination pressure regulator (U) and air control valve used on some models-(H) is the valve, (L) is the valve vacuum diaphragm and (T) is the air outlet to the cylinder head

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Fig. Fig. 3 The air shut-off valve (4) is mounted on top of the one way valve (5)

Air Pump

The air pump is belt driven from the engine. It is a rotary type pump with twin vanes guided by the rotor to prevent contact with the case. The inducted air is drawn through a filter which provides clean air for the Air Injection System. The pump requires no maintenance and must be replaced should the unit be defective.

Pressure Regulator Valve

The pressure regulator valve is located on the pump output side. It regulates the compressed air to a maximum pressure of 4.7 psi at 3000 rpm. Excess air pressure will open a spring controlled valve, and is expelled into the atmosphere.

  1. Connect pressure gauge on the outlet side of release valve. With the engine running at 3000 rpm, maximum pressure reading should be approximately 4.27 psi.

Anti Backfire Valve

The purpose of this valve is to prevent combustion of unburned gases caused by an overly rich mixture in the exhaust on deceleration. It is controlled by manifold vacuum through a connecting line. On deceleration, the vacuum pressure rises and opens a valve allowing air to enter the intake manifold. Upon a balance of vacuum within the valve, the valve closes and shuts off air supply to the intake manifold.

  1. Disconnect the pipe between the valve and the intake manifold.
  3. Accelerate engine and release to normal idle.
  5. During deceleration, air should be blown out of the valve outlet for approximately five seconds.
  7. If the duration is incorrect, the valve should be replaced.

Air Control Valve

The air control valve is located between the release valve and the anti backfire valve. Upon engine starting, the vacuum created in the intake manifold causes the anti backfire valve to open and allow air to enter the intake manifold. This air would weaken the mixture and prevent easy starting. For this reason, the air control valve remains in the closed position. After engine is operating and the air pressure is equal to or higher than that of the idle speed, the air compresses an internal diaphragm causing the valve to open and allowing air to pass.

One Way Valve

It is located in the input end of the air injector manifold. It has a spring loading diaphragm type valve which allows air to pass in one direction (to exhaust ports), and is there to protect the air pump from exhaust blow back.

  1. Remove the valve.
  3. Blow through it in the direction of air flow, by mouth. The air should go through the valve.
  5. Blow through in the opposite direction. The air should not go through. Change the valve if it is operating incorrectly.

Air Cut-Off Valve

The air cut-off valve is located downstream of the release valve. It is controlled by the carburetor choke cable and cuts off the injected air supply to the engine for purposes of cold engine starting.

  1. Adjust the choke cable to the choke butterfly.
  3. With choke cable adjusted, pull choke control knob all the way out and move the air shut-off flap, actuating lever as far as it will go towards the pressure regulator valve side. Then tighten set screw securing the cable to the air shut-off flap actuating lever.