GM Prizm/Nova 1985-1993 Repair Guide

Diagnosis and Testing - Nova

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ENGINE CRANKS BUT DOES NOT START



Check For Spark
  1. Disconnect the high tension spark plug wire from the spark plug.
  2.  
  3. Hold the end about 1 / 2 inch from the body of the car.
  4.  
  5. Crank the engine and see if spark occurs.
  6.  

NOTE:Do not crank for more than 1 or 2 seconds at a time on the 1988 EFI (VIN Code 5) engine.

  1. If spark does not occur, perform the following test:
  2.  

Check Power Source Line Voltage

See Figure 1

  1. Remove the distributor cap.
  2.  
  3. Set the ignition switch to the ON position.
  4.  
  5. Using a voltmeter, connect the positive probe to the ignition coil positive terminal and the negative probe to the body ground. The voltage reading should be approximately 12 volts.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Ignition line voltage test - 1985-88 VIN Code 4 engines

Signal Generator (Pick-up Coil)
1985-88 VIN CODE 4 CARBURETED ENGINE

See Figure 2

  1. Set the ignition switch to the OFF position.
  2.  
  3. Remove the distributor cap.
  4.  
  5. Disconnect the signal generator (pick-up coil) wire from the ignitor (module).
  6.  
  7. Measure the resistance between across the signal generator (pick-up coil). If the resistance is not 140-180 ohms, replace the pick-up coil and breaker plate.
  8.  



Click image to see an enlarged view

Fig. Fig. 2: Pickup coil resistance test - 1985-88 VIN Code 4 engines

1988 VIN CODE 5 FUEL INJECTED ENGINE

See Figure 3

  1. Set the ignition switch to the OFF position.
  2.  
  3. Remove the distributor cap.
  4.  
  5. Disconnect the signal generator (pick-up coil) wire from the ignitor (module).
  6.  
  7. Measure the resistance between the positive (+) and negative (-) terminals of the two signal generators (pick-up coils). If the resistance is not 140-180 ohms, replace the distributor.
  8.  



Click image to see an enlarged view

Fig. Fig. 3: Pickup coil resistance - 1988 VIN Code 5 engine

Air Gap Adjustment
VIN CODE 4 CARBURETED ENGINE

See Figure 4

  1. Remove the distributor cap. Inspect the cap for cracks, carbon tracks or a worn center contact. Cracks in the cap can be very hard to see. They are usually hairline thin and run in odd directions within the cap.Replace the cap if necessary, transferring the wires one at a time from the old cap to the new one.
  2.  
  3. Pull the ignition rotor (not the signal rotor) straight up and remove it. Replace it if the contacts are worn, burned or pitted. Do not file the contacts.
  4.  



Click image to see an enlarged view

Fig. Fig. 4: Checking the air gap - 1985-88 VIN Code 4 engines

  1. Turn the engine over (you may use a socket wrench on the front pulley bolt to do this) until the projection on the pickup coil is directly opposite the signal rotor tooth.
  2.  
  3. Get a non-ferrous (paper, brass, or plastic) feeler gauge of 0.012 in. (0.3mm), and insert it into the pick-up air gap. DO NOT use an ordinary metal feeler gauge! The gauge should just touch either side of the gap. The permissible range is 0.008-0.016 in. (0.20-0.40mm).
  4.  

The air gap on the Nova is not adjustable. If the gap is not within specifications, the pick-up coil (igniter) must be replaced.

1988 VIN CODE 5 FUEL INJECTED ENGINE

See Figure 5

The electronically controlled fuel injection system relies on the Electronic Control Module (ECM) for proper operation. Because the ECM needs to receive information from the distributor (and to control its function), there are two pickup coils in the distributor. Make sure you measure the gap to each coil.

  1. Remove the distributor cap. Inspect the cap for cracks, carbon tracks or a worn center contact. Cracks in the cap can be very hard to see. They are usually hairline thin and run in odd directions within the cap.Replace the cap if necessary, transferring the wires one at a time from the old cap to the new one.
  2.  
  3. Pull the ignition rotor (not the signal rotor) straight up and remove it. Replace it if the contacts are worn, burned or pitted. Do not file the contacts.
  4.  
  5. Turn the engine over (you may use a socket wrench on the front pulley bolt to do this) until the projection on the pickup coil is directly opposite a signal rotor tooth.
  6.  



Click image to see an enlarged view

Fig. Fig. 5: Measuring the air gap - 1988 VIN Code 5 engine

  1. Get a non-ferrous (paper, brass, or plastic) feeler gauge of 0.012 in. (0.3mm), and insert it into the air gaps between the signal rotor and the pickup coil projections on each side . DO NOT use an ordinary metal feeler gauge! The gauge should just touch either side of the gap. The permissible range for all models is 0.008-0.016 in. (0.2-0.4mm).
  2.  
  3. The air gap is not adjustable. Should it be out of specification, the entire distributor must be replaced.
  4.  

 
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