Toyota Cressida/Corona/Crown/MarkII 1970-1982 Repair Guide

Air Injection System

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OPERATION





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Fig. Fig. 1 Air injection system components-22R engine



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Fig. Fig. 2 Air injection system schematic with feedback off-22R engine



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Fig. Fig. 3 Air injection system schematic with feedback on-22R engine



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Fig. Fig. 4 Air injection system operating conditions



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Fig. Fig. 5 Air injection system without a catalytic converter



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Fig. Fig. 6 Typical Emission Component Locations-20R engine shown

A belt-driven pump supplies air to an injection manifold which has nozzles in each exhaust port. Injection of air at this point causes combustion of unburned hydrocarbons in the exhaust manifold rather than allowing them to escape into the atmosphere. An anti-backfire valve controls the flow of air from the pump to prevent backfiring which results from an overly rich mixture under closed throttle conditions. There are two types of antibackfire valve used on Toyota models: 1970-71 models use gulp valves; 1972-82 models air bypass valves.

A check valve prevents hot exhaust gas backflow into the pump and hoses, in case of a pump failure, or when the antibackfire valve is not working.

In addition, all 1975-82 engines have an Air Switching Valve (ASV). On engines without catalytic converters, the ASV is used to stop air injection under a constant heavy engine load condition.

On engines with catalytic converters, the ASV is also used to protect the catalyst from overheating, by blocking the injector air necessary for the operation of the converter.

Since 1975 on most passenger car engines, the pump relief valve is built into the ASV.

REMOVAL & INSTALLATION





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Fig. Fig. 7 Loosen the air pump mounting bolts ...



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Fig. Fig. 8 ... and slide the bolts out to remove the air pump

Air Pump
  1. Disconnect the air hoses from the pump.
  2.  
  3. Loosen the bolt on the adjusting link and remove the drive belt.
  4.  
  5. Remove the mounting bolts and withdraw the pump.
  6.  


WARNING
Do not pry on the pump housing. It may be distorted.

  1. Installation is in the reverse order of removal. Adjust the drive belt tension after installation. Belt deflection should be 1 / 2 - 3 / 4 inch with 22 lbs. pressure.
  2.  

Anti-Backfire Valve and Air Switching Valve
  1. Detach the air hoses from the valve, and electrical leads (if equipped).
  2.  
  3. Remove the valve securing bolt.
  4.  
  5. Withdraw the valve.
  6.  
  7. Installation is performed in the reverse order of removal.
  8.  

Check Valve
  1. Detach the intake hose from the valve.
  2.  
  3. Use an open-end wrench to remove the valve from its mounting.
  4.  
  5. Installation is the reverse of removal.
  6.  

Relief Valve

From 1975 on models with ASV-mounted relief valves, replace the entire ASV/relief valve as an assembly.

  1. Remove the air pump from the car.
  2.  
  3. Support the pump so that it cannot rotate.
  4.  


WARNING
Never clamp the pump in a vise. The aluminum case will be distorted.

  1. Use a bridge to remove the relief valve from the top of the pump.
  2.  
  3. Position the new relief valve over the opening in the pump.
  4.  

The air outlet should be pointing toward the left.

  1. Gently tap the relief valve home, using a block of wood and a hammer.
  2.  
  3. Install the pump on the engine, as outlined above.
  4.  

Air Injection Manifold
  1. Remove the check valve, as previously outlined.
  2.  
  3. Loosen the air injection manifold attachment nuts and withdraw the manifold.
  4.  

On some engines it may be necessary to remove the exhaust manifold first.

  1. Installation is in the reverse order of removal.
  2.  

Air Injection Nozzles
  1. Remove the air injection manifold as previously outlined.
  2.  
  3. Remove the cylinder head, as detailed in .
  4.  
  5. Place a new nozzle on the cylinder head.
  6.  
  7. Install the air injection manifold over it.
  8.  
  9. Install the cylinder head on the engine block.
  10.  

TESTING



Air Pump

WARNING
Do not hammer, pry, or bend the pump housing while tightening the drive belt or testing the pump.

BELT TENSION AND AIR LEAKS
  1. Before proceeding with the tests, check the pump drive belt tension to ensure that it is within specifications.
  2.  
  3. Turn the engine. If the pump has seized, the belt will slip, making a noise. Disregard any chirping, squealing, or rolling sounds from inside the pump. These are normal when it is turned by hand.
  4.  
  5. Check the hoses and connections for leaks. Hissing or a blast of air indicates a leak. Soapy water, applied lightly around the area in question, is a good method for detecting leaks.
  6.  

AIR OUTPUT


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Fig. Fig. 9 Attach a vacuum gauge to the supply hose of the anti-backfire valve to test the air pump output

  1. Disconnect the air supply hose at the anti-backfire valve.
  2.  
  3. Connect a vacuum gauge, using a suitable adaptor, to the air supply hose.
  4.  

If there are two hoses, plug the second one.

  1. With the engine at normal operating temperature, increase the idle speed and watch the vacuum gauge.
  2.  
  3. The airflow from the pump should be steady (between 2 and 6 psi). If it is unsteady or falls below specs, the pump is defective and must be replaced.
  4.  

Pump Noise

The air pump is normally noisy. As engine speed increases, the noise of the pump will rise in pitch. The rolling sound the pump bearings make is normal. But if this sound becomes objectionable at certain speeds, the pump is defective and will have to be replaced.

A continual hissing sound from the air pump pressure relief valve at idle, indicates a defective valve. Replace the relief valve.

If the pump rear bearing fails, a continual knocking sound will be heard. Since the rear bearing is not separately replaceable, the pump will have to be replaced as an assembly.

Anti-Backfire Valve

There are two different types of anti-backfire valve used with air injection systems. A bypass valve is used on 1971-82 engines, while 1970-71 engines use a gulp type anti-backfire valve. Test procedures for both types are given below.

GULP VALVE
  1. Detach the air supply hose which runs between the pump and the gulp valve.
  2.  
  3. Connect a tachometer and run the engine to 1,500-2,000 rpm.
  4.  
  5. Allow the throttle to snap shut. This should produce a loud sucking sound from the gulp valve.
  6.  
  7. Repeat this operation several times. If no sound is present, the valve is not working or else the vacuum connections are loose.
  8.  
  9. Check the vacuum connections. If they are secure, replace the gulp valve.
  10.  

BYPASS VALVE
  1. Detach the hose, which runs from the bypass valve to the check valve, at the bypass valve hose connection.
  2.  
  3. Connect a tachometer to the engine. With the engine running at normal idle speed, check to see that air is flowing from the by-pass valve hose connection.
  4.  
  5. Speed up the engine so that it is running at 1,500-2,000 rpm. Allow the throttle to snap shut. The flow of air from the bypass valve at the check valve hose connection should stop momentarily and air should then flow from the exhaust port on the valve body or the silencer assembly.
  6.  
  7. Repeat Step 3 several times. If the flow of air is not diverted into the atmosphere from the valve exhaust port or if it fails to stop flowing from the hose connection, check the vacuum lines and connections. If these are tight, the valve is defective and requires replacement.
  8.  
  9. A leaking diaphragm will cause the air to flow out both the hose connection and the exhaust port at the same time. If this happens, replace the valve.
  10.  

Check Valve
  1. Before starting the test, check all of the hoses and connections for leaks.
  2.  
  3. Insert a suitable probe into the check valve and depress the plate. Release it. The plate should return to its original position against the valve seat. If binding is evident, replace the valve.
  4.  
  5. With the engine running at normal operating temperature, gradually increase its speed to 1,500 rpm. Check for exhaust gas leakage. If any is present, replace the valve assembly.
  6.  

Vibration and flutter of the check valve at idle speed is a normal condition and does not mean that the valve should be replaced.

Air Switching Valve (ASV)
1975-82 20R AND 22R ENGINES
  1. Start the engine and allow it to reach normal operating temperature and speed.
  2.  
  3. At curb idle, the air from the by-pass valve should be discharged through the hose which runs to the ASV.
  4.  
  5. When the vacuum line to the ASV is disconnected, the air from the by-pass valve should be diverted out through the ASV to-air cleaner hose. Reconnect the vacuum line.
  6.  
  7. Disconnect the ASV-to-check valve hose and connect a pressure gauge to it.
  8.  
  9. Increase the engine speed. The relief valve should open when the pressure gauge registers 2.7-6.5 psi.
  10.  
  11. If the ASV fails any of the above tests, replace it. Reconnect all hoses.
  12.  

1975-79 M SERIES ENGINES


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Fig. Fig. 10 Testing the Air Switching Valve (ASV) on the 4M engine



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Fig. Fig. 11

  1. Start the engine and allow it to reach normal operating temperature and speed.
  2.  
  3. At curb idle, air from the pump should be discharged through the hose which runs to the check valve.
  4.  
  5. Race the engine and allow the throttle valve to snap shut. The air from the pump should be discharged into the air cleaner.
  6.  
  7. Disconnect the ASV-to-check valve hose and connect a pressure gauge to it.
  8.  
  9. Increase the engine speed gradually. The relief valve should open when the gauge registers 3.7-7.7 psi. Reconnect the check valve hose.
  10.  
  11. Unfasten the wiring connector and the hoses from the solenoid valve, which is attached to the ASV. Air should pass through the solenoid valve when either the top or bottom port is blown into.
  12.  
  13. Connect a 12v power source to the terminals on the valve. No air should flow through the valve when either port is blown into.
  14.  
  15. If the solenoid valve or the ASV fail any of the above tests, replace either or both of them, as necessary.
  16.  

Vacuum Delay Valve
1975-82 20R AND 22R ENGINES

The vacuum delay valve is located in the line which runs from the intake manifold to the vacuum surge tank.

  1. Remove the vacuum delay valve from the vacuum lines. Be sure to note which end points toward the intake manifold.
  2.  
  3. When air is blown in from the ASV (surge tank) side, it should pass through the valve freely.
  4.  
  5. When air is blown in from the intake manifold side, a resistance should be felt.
  6.  
  7. Replace the valve if it fails either of the above tests.
  8.  
  9. Install the valve in the vacuum line, being careful not to install it backward.
  10.  

 
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