The plug wires carry a very tiny amount of current under extremely high voltage. The conductors inside must offer some resistance to flow of current, or operation of a radio in the car, or even nearby, would be impossible. For these reasons, these wires deteriorate steadily and often produce puzzling and unexpected lapses in performance. The most typical evidence of wire problems is the sudden failure of the car to start on a damp morning.
The wires should be inspected frequently for full seating at the plugs and distributor cap towers. Before inspection, wipe the wires carefully with a cloth slightly moistened with a non-flammable solvent so it will be easier to see cracks or other damage. The insulation and all rubber boots should be flexible and free of cracks. Replace the wires as a set as soon as any such problems develop.
Unfortunately, the invisible conductors inside high quality wires can deteriorate before evidence of poor insulation exists. You can remove such wires and test the resistance if you have an ohmmeter. Measure the length of each wire with a ruler and then multiply the length by the figures given, in order to measure total resistance. Resistance must be 250-1000 ohms per inch (25mm) or 3,000-12,000 ohms per foot (305mm). If you wish to check the cap at the same time, you can run your test between the spark plug end of the plug wire and the contact at the center of the inside of the cap.
If you do not have an ohmmeter, you may want to take you car to a mechanic or diagnostic center with an oscilloscope type of diagnosis system. This unit will read the curve of ignition voltage and uncover problems with wires, or any other component, easily. You may also want to refer to the previous procedures on spark plug analysis, as looking at the plugs may help you to identify wire problems.
REMOVAL & INSTALLATION
Always replace the wires (match old wire to new wire for correct length) one at a time in order to avoid having to study and follow the firing order diagrams.
- Pull the spark plug cable end off of the distributor cap.
- Twist and pull the spark plug cable boot off of the spark plug. Do not pull on the cable itself-pull on the boot.
- Note the routing of the spark plug cable, then remove from any cable retainers or clips.
- Push the spark plug cable boots onto the distributor cap, then the spark plugs. Make sure they are seated totally on the distributor and spark plug nipples.
- Insert the spark plug cable into the retainers or clips.
- Repeat this procedure for each spark plug cable.