Mazda Trucks 1972-1986 Repair Guide

Timing

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INSPECTION AND ADJUSTMENT



Piston Engines
  1. Raise the hood and clean and mark the timing marks. Chalk or fluorescent paint makes a good, visible mark.
  2.  
  3. Disconnect the vacuum line to the distributor and plug the disconnected line. Disconnect the line at the vacuum source, not at the distributor.
  4.  
  5. Connect a timing light to the front (No. 1) cylinder, a power source and ground. Follow the manufacturer's instructions.
  6.  
  7. Connect a tachometer to the engine.
  8.  
  9. Start the engine and reduce the idle to 700-750 rpm to be sure that the centrifugal advance mechanism is not working.
  10.  
  11. With the engine running, shine the timing light at the timing pointer and observe the position of the pointer in relation to the timing mark on the crankshaft pulley. 1972 49 states/Canada models have three notches on the pulley; all others have two. Looking straight down on the marks, the one on the left is ATDC, the one in the center is TDC, the one on the right is BTDC. On 1973 and later models, the one on the left is TDC, the one on the right is BTDC.
  12.  
  13. If the timing is not as specified, adjust the timing by loosening the distributor hold-down bolt and rotating the distributor in the proper direction. When the proper ignition timing is obtained, tighten the hold-down bolt on the distributor.
  14.  
  15. Check the centrifugal advance mechanism by accelerating the engine to about 2,000 rpm. If the ignition timing advances, the mechanism is working properly.
  16.  
  17. Stop the engine and remove the timing light.
  18.  
  19. Reset the idle to specifications.
  20.  
  21. Remove the tachometer.
  22.  

Rotary Engines See Figures 1, 2 and 3

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Fig. Fig. 1: Timing marks on the rotary engine. Numbers preceded by a minus sign (-) are ATDC



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Fig. Fig. 2: Schematic diagram of timing procedures for the rotary engine



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Fig. Fig. 3: The external adjusting lever (arrow) on rotary engine distributors

  1. Connect a tachometer to the engine.
  2.  
  3. Disconnect and plug the vacuum tube on the distributor.
  4.  
  5. Connect a timing light to the wire from the leading (lower) plug of the front rotor housing.
  6.  
  7. Start the engine and run it idle speed.
  8.  
  9. Shine the timing light on the indicator pin located on the front cover.
  10.  
  11. If the leading timing mark is not correctly aligned with the pointer, stop the engine.
  12.  
  13. Loosen the distributor locknut and rotate the distributor housing (with the engine running) until the timing marks align. Stop the engine and tighten the distributor locknut.
  14.  
  15. Recheck the timing.
  16.  
  17. Change the connection of the timing light to the wire from the trailing (top) plug in the front rotor housing.
  18.  
  19. Start the engine and shine the timing light at the indicator pin. If the trailing timing falls within the specifications, no further adjustments are necessary.
  20.  
  21. If the trailing timing is not within specifications, proceed with the rest of the procedure.
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  23. If the trailing timing is not within specifications, adjust the trailing and leading timing as follows:
  24.  
  25. Adjust the trailing timing to specification by rotating the distributor body, as in Step 7.
  26.  
  27. Check the leading timing again and record how much it differs from specification.
  28.  
  29. Remove the distributor cap and rotor.
  30.  
  31. Loosen the breaker base setscrews (the ones directly opposite each other near the outside of the distributor base plate until the correct leading plug timing is obtained again.
  32.  
  33. Recheck the timing. If the leading and trailing plug timing marks should both be aligned (or within specifications). If not, repeat the procedure until they are.
  34.  

 
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