Jeep CJ/Scrambler 1971-1986 Repair Guide

Ignition Timing Adjustment

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See Figures 1, 2, 3, 4, 5, 6, 7 and 8

POINT TYPE IGNITION



  1. Locate the timing marks on the pulley and on the front of the engine.
  2.  
  3. Clean off the timing marks so you can see them.
  4.  
  5. Mark the timing marks with a piece of chalk or white paint. Mark the one on the engine that will indicate correct timing when it is aligned with the mark on the pulley or flywheel.
  6.  
  7. Attach a tachometer to the engine.
  8.  
  9. Attach a timing light according to the manufacturer's instructions. If the timing light has three wires, one is attached to the no. 1 spark plug lead with an adapter. The other two are connected to the battery. The red one goes to the positive side of the battery and the black one to the negative terminal.
  10.  
  11. Disconnect the vacuum line to the distributor at the distributor. Plug the end of the hose.
  12.  
  13. Check to make sure that all of the wires clear the fan and then start the engine.
  14.  
  15. If there is an idle speed solenoid, disconnect it.
  16.  
  17. Aim the timing light at the timing marks. If the marks that you put on the pulley and the engine are aligned, the timing is correct. Turn off the engine and remove the tachometer and the timing light. If the marks are not in alignment, proceed to the following steps.
  18.  
  19. Turn off the engine.
  20.  
  21. Loosen the distributor lockbolt just enough so that the distributor can be turned with a little effort.
  22.  
  23. Start the engine. Keep the cords of the timing light clear of the fan.
  24.  
  25. With the timing light aimed at the pulley and the marks on the engine, turn the distributor in the direction of rotor rotation to retard the spark, and in the opposite direction of rotor rotation to advance the spark. Line up the marks on the pulley and the engine.
  26.  
  27. When the marks are aligned, tighten the distributor lockbolt and recheck the timing with the timing light to make sure that the distributor did not move when you tightened the distributor lockbolt.
  28.  
  29. Turn off the engine and remove the timing light.
  30.  

ELECTRONIC IGNITION



  1. Warm up the engine to normal operating temperature. Stop the engine and connect the timing light to the No. 1 (left front on V8, front on 4- or 6-cylinder) spark plug wire. Clean off the timing marks and mark the pulley notch and timing scale with white chalk.
  2.  
  3. Disconnect and plug the vacuum line at the distributor. This is done to prevent any distributor vacuum advance.
  4.  
  5. Start the engine and adjust the idle to 500 rpm with the carburetor idle speed screw on 1975-77 Jeep vehicles. On 1978 and later models, set the idle speed to the figure shown on the underhood sticker. This is done to prevent any distributor centrifugal advance. If there is a throttle stop solenoid, disconnect it electrically.
  6.  
  7. Aim the timing light at the pointer marks. Be careful not to touch the fan, because it may appear to be standing still. If the pulley notch isn't aligned with the proper timing mark (refer to the Tune-Up Specifications chart), the timing will have to be adjusted.
  8.  

TDC or Top Dead Center corresponds to 0 degrees. B, or BTDC, or Before Top Dead Center, may be shown as A for Advanced on a V8 timing scale. R on a V8 timing scale means Retarded, corresponding to ATDC, or After Top Dead Center.

  1. Loosen the distributor clamp locknut. You can buy trick wrenches that make this task a lot easier. Turn the distributor slowly to adjust the timing, holding it by the base and not the cap. Turn counterclockwise to advance timing (toward BTDC), and clockwise to retard (toward TDC or ATDC).
  2.  
  3. Tighten the locknut. Check the timing again, in case the distributor moved slightly as you tightened it.
  4.  
  5. Replace the distributor vacuum line and correct the idle speed to that specified in the Tune-Up Specifications chart.
  6.  
  7. Stop the engine and disconnect the timing light.
  8.  



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Fig. Fig. 1: Timing marks on the 4-134



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Fig. Fig. 2: Timing marks on the 225 V6



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Fig. Fig. 3: Timing marks on the 6-232 and 6-258 with point type ignition system



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Fig. Fig. 4: Timing marks on the 8-304



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Fig. Fig. 5: Timing marks on the 4-150



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Fig. Fig. 6: Timing marks on the 4-151



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Fig. Fig. 7: Timing marks on the 6-258 with electronic ignition



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Fig. Fig. 8: Turn the distributor with your hand, while aiming the timing light at the timing marks

 
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