GM Prizm/Nova 1985-1993 Repair Guide

Ignition Coil

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TESTING



See Figures 1 and 2

This test requires the use of an ohmmeter. When using this tool, make sure the scale is set properly for the range of resistance you expect to encounter during the test. Always perform these tests with the ignition OFF.

  1. Disconnect the distributor cap and set it aside. The spark plug wires may be left attached to the cap. Remove the rotor and the dust cover(s).
  2.  
  3. Using the ohmmeter, measure the resistance between the positive (+) and negative (-) terminals on the coil. The resistance on the primary side of the coil (when cold) should be:

    1985-88 VIN Code 4 engine: 0.3-0.5-
     
    1986-88 VIN Code 4 engine: 0.4-0.5-
     
    1988 VIN Code 5 engine: 0.5-0.7-
     
    1989-90 VIN Code 6 engine: 1.28-1.56-
     
    1990 VIN Code 5 engine: 0.4-0.5-
     
    1991-92 VIN Code 5 engine: 1.28-1.56-
     
    1991-92 VIN Code 6 engine: 0.4-0.5-
     
    1993 All engines: 1.11-1.75-
     

  4.  

  1. Using the ohmmeter, measure the resistance between the positive terminal and the center (high tension) terminal. (This is the terminal to which the coil attaches in the cap.) The resistance on the secondary side should be:

    1985 VIN Code 4 engine: 7,500-10,500-
     
    1985- 88 VIN Code 4 engine: 7,500-10,400-
     
    1988 VIN Code 5 engine: 0.4-0.5-
     
    1988 VIN Code 5 engine: 11,000-16,000-
     
    1990 VIN Code 5 engine: 10,200-13,800-
     
    1989-90 VIN Code 6 engine: 10,400-14,000-
     
    1991-92 VIN Code 5 engine: 10,400-14,000-
     
    1991-92 VIN Code 6 engine: 10,200-13,800-
     
    1993 All engines: 9,000-15,700-
     

  2.  

  1. Coils measuring outside either of these ranges must be replaced.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Checking the coil primary resistance



Click image to see an enlarged view

Fig. Fig. 2: Checking the coil secondary resistance

REMOVAL & INSTALLATION



See Figure 3

External Coil

External coils (coils which are not built into the distributor) are easily replaced by the following procedure:

  1. Make certain the ignition is off and the key is removed.
  2.  
  3. Disconnect the high tension wire (running between the coil and the distributor) from the coil.
  4.  
  5. Label and disconnect the low tension wires from the coil.
  6.  
  7. Loosen the coil bracket and remove the coil. Install the new coil and tighten the bracket.
  8.  



Click image to see an enlarged view

Fig. Fig. 3: The coil is easily removed with the distributor out of the engine

  1. Attach the low tension wires first, then the coil wire.
  2.  

Internal Coil

The internal coils found within the distributor can be changed without removing the distributor. A selection of various short screwdrivers may be required for access to the screws.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the distributor cap with the wires attached and set it aside.
  4.  
  5. Remove the rotor and the dust cover(s).
  6.  
  7. Remove the nuts and disconnect the wires from the terminals on the coil.
  8.  
  9. Remove the 4 retaining screws and remove the coil. Note that later cars have a gasket below the coil - remove it carefully to avoid damage.
  10.  
  11. Install the coil, paying close attention to the gasket and its placement.
  12.  
  13. Connect the wiring to the coil and be careful of the routing of the wires.
  14.  
  15. Install the dust cover(s), the rotor and the cap.
  16.  
  17. Reconnect the battery.
  18.  

 
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