How to Inspect Spark Plug Wires

Spark plug wires deliver the spark from your engine’s ignition system to the spark plugs. Plug wires consist of a metal wires that are wrapped in protective rubber insulation. Over time, the rubber protecting the wire can dry out and crack. If this happens, the spark can arc and become weak as it travels from the distributor to the spark plug. Inspecting spark plug wires is an easy task, as is replacing them if they are damaged.

Instructions

1. Open the engine bay. Locate the spark plug wires. These will be fastened in a group to the distributor on one end. From there, the plug wires run to each cylinder, one to each cylinder, the exception being twin-plug engines, which are relatively rare and have two spark plugs and two wires for each cylinder. The distributor will be on the side or front of the engine.

2. With the engine off, inspect the entire length of each plug wire. The wires should be smooth and pliable from one end to the other. Bend the wires to make sure they are not dried out. Look for cracks, burns or tears in the insulation.

3. Inspect the boots at each end of the wire. The boot should go all the way around the wire and should have no tears or missing pieces.

4. Pull the plug wires off of the distributor terminals, one at a time, to inspect the ends. Pulling off one at a time ensures that the plug wires remain in the same order so as not to change the firing order of the engine. Inspect the metal contacts at the end of the distributor, looking for burn marks in the metal.

5. Pull the wires off of the spark plugs and inspect them one at a time, reinstalling them as you go. Grasp the wires at the base as you remove them. Inspect the metal terminals for burns.

6. Replace spark plug wires that are determined to be bad. It is preferable to replace the entire set of plug wires at once. A set of wires can cost anywhere from around $30. They are as easy to install as to inspect.

References

• NASCAR: Careful inspection of plug wires can avoid problems