Chrysler Full-Size Trucks 1989-1996 Repair Guide

Spark Plug Wires


Spark plug wires transfer electrical current from the distributor to the individual spark plugs at each cylinder. The wires are of nonmetallic construction and have a built-in resistance. Most of the wires found on vehicles covered by this guide provide suppression of radio frequency emissions from the ignition system.


Visually inspect the spark plug cables for burns, cuts, or breaks in the insulation. Check the spark plug boots and the nipples on the distributor cap and coil. Terminals should fit tightly. Loose connections provide poor conductivity and are an invitation for corrosion which will further diminish the strength of the spark. Replace any damaged wiring. If no physical damage is obvious, the wires can be checked with an ohmmeter for excessive resistance. Minimum spark plug resistance should be 250 ohms per inch (635 ohms per centimeter) and maximum resistance should be 1000 ohms per inch (2540 ohms per centimeter).


  1. Mark all the spark plug wires near the cap with their cylinder number for identification purposes.
  3. Grasp and twist the spark plug boot until the boot comes free of the plug. Do not pull on the wire.
  5. Repeat for the other spark plug wires.

To install:
  1. When installing a new set of spark plug cables, replace the cables one at a time so there will be no mix-up. Start by replacing the longest cable first. Install the boot firmly over the spark plug. Route the wire exactly the same as the original. Insert the nipple firmly into the tower on the distributor cap.
  3. Repeat the process for each cable.