GM Corvette 1984-1996 Repair Guide

Spark Plug Wires

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TESTING



See Figure 1



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Fig. Fig. 1: Checking individual plug wire resistance with a digital ohmmeter

At every tune-up/inspection, visually check the spark plug cables for burns cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil. Replace any damaged wiring.

Every 50,000 miles (80,000 Km) or 60 months, the resistance of the wires should be checked with an ohmmeter. Wires with excessive resistance will cause misfiring, and may make the engine difficult to start in damp weather.

To check resistance, connect one lead of an ohmmeter to each end of the wire. Replace any wire which shows a resistance over 30,000 ohms. Generally speaking, it is preferable that resistance be below 25,000 ohms, but 30,000 ohms must be considered the outer limit of acceptability. It should be remembered that resistance is also a function of length; the longer the wire, the greater the resistance. Thus, if the wires on your car are longer than the factory originals, resistance will be higher, quite possible outside these limits.

Wire length can therefore be used to determine appropriate resistance values:



0-15 in. (0-38cm)-3,000-10,000 ohms
 
15-25 in. (38-64cm)-4,000-15,000 ohms
 
25-35 in. (64-89cm)-6,000-20,000 ohms
 
Wire over 35 in. (89cm)-25,000 ohms
 

REMOVAL & INSTALLATION



See Figures 2, 3, 4 and 5

When installing new wires, replace them one at a time to avoid mix-ups. If it becomes necessary to remove all of the wires from the distributor cap or coil packs at one time, take the time to label the distributor cap/coil pack towers to denote the cylinder number of the wire for that position. When this is done, incorrect positioning of wires can more easily be avoided. Start by replacing the longest one first. Route the wire over the same path as the original and secure in place.

  1. Disconnect the negative battery cable.
  2.  
  3. Note the locations of the spark plug wires, retainers, spark plug and distributor or ignition coil pack.
  4.  
  5. If removing all of the spark plug wires, make sure to label the wires and their corresponding positions on the coil or distributor with the proper cylinder number. This will greatly ease installation, preventing much confusion.
  6.  
  7. Twist the spark plug boot 1 / 2 turn in each direction before removing, then pull on the boot to remove the wire from the spark plug. Always pull on the boot, never the wire itself.
  8.  
  9. Twist the spark plug boot 1 / 2 turn in each direction, then pull the boot to disconnect the spark plug from the distributor or ignition coil, as applicable. Never pull on the spark plug wire, only the plug boot.
  10.  
  11. Remove the spark plug wire from any retainers, then remove it from the vehicle.
  12.  



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Fig. Fig. 2: Spark plug wire routing and cylinder identification-5.7L (VIN 8) engine



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Fig. Fig. 3: Spark plug wire routing and cylinder and coil identification-1990-95 5.7L (VIN J) engine



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Fig. Fig. 4: Spark plug wire routing and cylinder identification-5.7L (VIN P) engine



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Fig. Fig. 5: Distributor cylinder identification-1996 vehicles

To install:
  1. Route the wires in the proper location as noted during removal. The wires must be properly routed; you can refer to the accompanying illustrations for spark plug wire routing and retaining clip location.
  2.  
  3. Apply a small amount of silicone dielectric compound to the spark plug wire boots and ignition coil or distributor towers.
  4.  
  5. Attach the spark plug wire to the to the ignition coil pack or distributor, and spark plug, pushing it on firmly. A click should be felt or heard when the boot is on properly.
  6.  
  7. Check that the boot is properly installed by pushing sideways on the installed boots; they should be stiff with only slight looseness. If the boot feels like its not on properly, reseat the boot by twisting it 1 / 2 turn, pulling the boot off, then reinstalling the boot.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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