Subaru Coupes/Sedans/Wagons 1985-1996 Repair Guide

Spark Plug Wires

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TESTING



See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: Checking plug wire resistance through the distributor cap with an ohmmeter



Click image to see an enlarged view

Fig. Fig. 2: 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 coil. Replace any damaged wiring.

Every 30,000 miles (48,000 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, remove the distributor cap, leaving the wires attached. Connect one lead of an ohmmeter to an electrode within the cap. Connect the other lead to the corresponding spark plug terminal (remove it from the plug for this test). Replace any wire which shows excessive resistance.

It should be remembered that resistance is also a function of length; the longer the wire the greater the resistance. The following is a guide to the resistance of spark plug wires:



Up to 15 in. (381mm): 3000-10,000 ohms
 
15-25 in. (381-635mm): 4000-15,000 ohms
 
25-35 in. (635-889mm): 6000-20,000 ohms
 
Over 35 in. (889mm): 6000-25,000 ohms
 

If the spark plug wires are found to be defective, replace the wires one at a time. Install the boot firmly over the spark plug. Route the wire over the same path as the original. Insert the nipple firmly into the tower on the cap or the coil.

A little smear of dielectric grease inside the boots of the spark plug wires will prevent corrosion, and aid in boot removal the next time the plugs are serviced.

REMOVAL & INSTALLATION



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: Twist off the plug wire from the distributor cap or coil pack-2.2L engine shown

  1. Label each spark plug wire before removing. If you are removing more than one wire at a time, mark both the plug wire and the corresponding location on the distributor cap, or ignition coil pack.
  2.  
  3. Remove the plug wire from the end of the spark plug by grasping the wire by the rubber boot. If the boot sticks to the plug, remove it by twisting back and forth, then pulling up on the boot. DO NOT pull the wire itself or you will damage the core.
  4.  
  5. Remove the plug wire from the distributor cap or ignition coil pack, by grasping the wire by the rubber boot and pulling upward. If the boot sticks, twist back and forth on the boot, then pull up on the boot. DO NOT pull the wire itself or you will damage the core.
  6.  

To install:
  1. Insert the smaller end of the plug wire into the distributor cap until tight.
  2.  
  3. Insert the other end of the spark plug wire on to the correct spark plug, by twisting the plug wire down on the spark plug.
  4.  
  5. Continue until all wires are installed.
  6.  

 
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