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, remove each plug wire and test one at a time. Connect one lead of an ohmmeter to the electrode within the wire on the cap end; connect the other lead to the corresponding spark plug terminal end of the wire. Replace any wire which shows a resistance of over 25,000 ohms.