Mazda Trucks 1972-1986 Repair Guide

Air Injection System

Print

The air injection system used on the Mazda rotary engine differs from the type used on a conventional piston engine in two respects:

  1. Air is not only supplied to burn the gases in the exhaust ports, but it is also used to cool the thermal reactor.
  2.  
  3. A three-way air control valve is used in place of the conventional anti-backfire and diverter valves. It contains an air cut-out valve, a relief valve, and a safety valve.
  4.  

Air is supplied to the system by a normal vane type air pump. The air flows from the pump to the air control valve, where it is routed to the air injection nozzles to cool the thermal reactor or, in the case of a system malfunction, to the air cleaner. A check valve, located beneath the air control valve seat, prevents the back-flow of hot exhaust gases into the air injection system in case of air pressure loss.

Air injection nozzles are used to feed air into the exhaust ports, just as in a conventional piston engine.

TESTING Air Pump



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Test connections for the air pump on rotary engines

  1. Check the air pump drive belt tension by applying 22 lbs. of pressure halfway between the water pump and air pump pulleys. The belt should deflect 6-9mm (0.236-0.354 in.). Adjust the belt if necessary, or replace it if it is cracked or worn.
  2.  
  3. Turn the pump by hand. If it has seized, the drive belt will slip, producing noise.
  4.  

Disregard any chirping squealing, or rolling sounds coming from inside the pump; these are normal when it is being turned by hand.

  1. Check the hoses and connections for leaks. Hissing or a blast of air is indicative of a leak. Soapy water, applied around the area in question, is a good method of detecting leaks.
  2.  
  3. Connect a pressure gauge between the air pump and the air control valve with a T-fitting.
  4.  
  5. Plug the other hose connections (outlets) on the air control valve, as illustrated.
  6.  


CAUTION
Be careful not to touch the thermal reactor; severe burns will result.

  1. With the engine at normal idle speed, the pressure gauge should read 0.48-0.68 psi. Replace the air pump if it is less than this.
  2.  
  3. If the air pump is not defective, leave the pressure gauge connected but unplug the connections at the air control valve and proceed with the next test.
  4.  

Air Control Valve See Figures 2 and 3



Click image to see an enlarged view

Fig. Fig. 2: Cross-section of the air control valve



Click image to see an enlarged view

Fig. Fig. 3: Test connections for the air control valve


CAUTION
When testing the air control valve, avoid touching the thermal reactor as severe burns will result.

  1. Test the air control valve solenoid as follows:
    1. Turn the ignition switch off and on. A click should be heard coming from the solenoid. If no sound is audible, check the solenoid wiring.
    2.  
    3. If no defect is found in the solenoid wiring, connect the solenoid directly to the truck's battery. If the solenoid still does not click, it is defective and must be replaced. If the solenoid works, then check the components of the air flow control system. See below.
    4.  

  2.  
  3. Start the engine and run it at idle speed. The pressure gauge should still read 0.37-0.75 psi. No air should leak from the two outlets which were unplugged.
  4.  
  5. Increase the engine speed to 3,500 rpm for manual transmissions; 3,000 rpm for automatic transmissions. The pressure gauge should now read 1.2-2.8 psi and the two outlets still should not be leaking air.
  6.  
  7. Return the engine to idle.
  8.  
  9. Disconnect the solenoid wiring. Air should now flow from the outlet marked A in the illustration, but not from the outlet marked B. The pressure gauge reading should remain the same as in Step 2.
  10.  
  11. Reconnect the solenoid.
  12.  
  13. If the relief valve is faulty, air sent from the air pump will flow into the cooling passages of the thermal reactor when the engine is at idle speed.
  14.  
  15. If the safety valve is faulty, air will flow into the air cleaner when the engine is idling.
  16.  
  17. Replace the air control valve if it fails to pass any one of the above tests. Remember to disconnect the pressure gauge.
  18.  

Check Valve See Figure 4



Click image to see an enlarged view

Fig. Fig. 4: Check the one-way valve operation, as illustrated

  1. Remove the check valve, as detailed below.
  2.  
  3. Depress the valve plate to see if it will seat properly.
  4.  
  5. Measure the free length of the valve spring; it should be 31mm (1.22 in.) on trucks with manual transmission; 19mm (0.748 in.) on trucks with automatic transmission.
  6.  
  7. Measure the installed length of the spring; it should be 17mm (0.669 in.). Replace the check valve if it is not up to specifications.
  8.  

REMOVAL & INSTALLATIONAir Pump



  1. Remove the air cleaner assembly from the carburetor.
  2.  
  3. Loosen, but do not remove, the adjusting link bolt.
  4.  
  5. Push the pump toward the engine to slacken belt tension and remove drive belt.
  6.  
  7. Disconnect the air supply hoses from the pump.
  8.  
  9. Unfasten the pump securing bolts and remove the pump.
  10.  


WARNING
Do not pry on the air pump housing during removal and do not clamp the housing in a vise once the pump has been removed. Any type of heavy pressure applied to the housing will distort it.

  1. Installation is performed in the reverse order of removal. Adjust the belt tension by moving the air pump to the specification given in the Testing section, above.
  2.  

Air Control Valve


CAUTION
Remove the air control valve only after the thermal reactor has cooled sufficiently to prevent the danger of a serious burn.

  1. Remove the air cleaner assembly.
  2.  
  3. Unfasten the leads from the air control valve solenoid.
  4.  
  5. Disconnect the air hoses from the valve.
  6.  
  7. Loosen the screws which secure the air control valve and remove the valve.
  8.  
  9. Valve installation is performed in the reverse order of removal.
  10.  

Check Valve

  1. Perform the air control valve removal procedure, detailed above. Be sure to pay attention to the CAUTION.
  2.  
  3. Remove the check valve seat.
  4.  
  5. Withdraw the valve plate and spring.
  6.  
  7. Install the check valve in the reverse order of removal.
  8.  

Air Injection Nozzle

  1. Remove the gravel shield from underneath the truck.
  2.  
  3. Perform the oil pan removal procedure as detailed in "Engine Lubrication," above.
  4.  
  5. Unbolt the air injection nozzles from both of the rotor housings.
  6.  
  7. Nozzle installation is performed in the reverse order of removal.
  8.  

 
label.common.footer.alt.autozoneLogo