GM Full Size Vans 1967-1986 Repair Guide

Ignition Coil

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TESTING



See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: View of the "coil in cap'' distributor and related components



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Fig. Fig. 2: Testing the ignition coil

  1. A six cylinder EST distributor with coil-in-cap is illustrated, the 8-cyl EST distributor is similar.
  2.  
  3. Detach the wiring connector from the distributor cap.
  4.  
  5. Turn the four latches and remove the cap and coil assembly from the lower housing.
  6.  
  7. Connect ohmmeter. Test 1.
  8.  
  9. Reading should be zero, or nearly zero. If not replace coil.
  10.  
  11. Connect ohmmeter both ways. Test 2. Use the high scale. Replace coil only if both readings are infinite.
  12.  
  13. If coil is good, go to step 13.
  14.  
  15. Remove coil cover attaching screws and lift off cover.
  16.  
  17. Remove ignition coil attaching screws and lift coil with leads from cap.
  18.  
  19. Remove ignition coil arc seal.
  20.  
  21. Clean with soft cloth and inspect cap for defects. Replace if necessary.
  22.  
  23. Assemble the new coil and cover to cap.
  24.  
  25. .On all distributors, including distributors with Hall Effect Switch identified in step 27, remove rotor and pick-up coil leads from module.
  26.  
  27. Connect ohmmeter Test 1 and then test 2.
  28.  
  29. If vacuum unit is used, connect a vacuum source to the vacuum unit. Replace the vacuum unit if inoperative. Observe the ohmmeter throughout vacuum range: flex leads by hand without vacuum to check for intermittent opens.
  30.  
  31. Test 1 should read infinite at all times. Test 2 should read steady at one value within 500-1,500 ohms range.
  32.  

Ohmmeter may deflect if operating vacuum unit causes teeth to align. This is not a defect.

  1. If pickup coil is defective go to step 18. If coil is okay, go to step 23.
  2.  
  3. Mark distributor shaft and gear so they can be reassembled in the same position.
  4.  
  5. Drive out poll pin.
  6.  
  7. Remove gear and pull shaft assembly from distributor.
  8.  
  9. Remove three attaching screws and remove the magnetic shield.
  10.  
  11. Remove retaining ring and remove pickup coil, magnet and pole piece.
  12.  
  13. Remove two module attaching screws, and the capacitor attaching screw. Lift module, capacitor and harness assembly from base.
  14.  
  15. Disconnect wiring harness from module.
  16.  
  17. Check the module with an approved module tester.
  18.  
  19. Install module, wiring harness, and capacitor assembly. Use silicone lubricant on housing under module.
  20.  
  21. The procedures previously covered, Steps 1-26, also apply to distributors with Hall Effect Switches.
  22.  

REMOVAL & INSTALLATION



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: View of the ignition coil attaching screws

  1. Detach the wiring connector from the distributor cap.
  2.  
  3. Turn the four latches and remove the cap and coil assembly from the lower housing.
  4.  
  5. Remove coil cover attaching screws and lift off cover.
  6.  
  7. Remove ignition coil attaching screws and lift coil with leads from cap.
  8.  
  9. Remove ignition coil arc seal.
  10.  
  11. Clean with soft cloth and inspect cap for defects. Replace if necessary.
  12.  
  13. Assemble the new coil and cover to cap.
  14.  

 
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