See Figure 1
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. Replace any damaged wiring. If no physical damage is obvious, the wires can be checked with an ohmmeter for excessive resistance.
Remove the distributor cap and leave the wires connected to the cap. Connect one lead of the ohmmeter to the corresponding electrode inside the cap and the other lead to the spark plug terminal (remove it from the spark plug for the test). Replace any wire which shows over 50,000 ohms. Generally speaking, however, resistance should not run over 35,000 ohms and 50,000 ohms should be considered the outer limit of acceptability. It should be remembered that wire resistance is a function of length. The longer the cable, the greater the resistance. Thus, if the cables on your car are longer than the factory originals, resistance will be higher and quite possibly outside of these limits.
REMOVAL & INSTALLATION
If the wires are being replaced, remove one wire and match the length with the new wire. Install the new wire before removing the next old one. If the wires are to be reinstalled, label and remove them one at a time from the distributor cap before disconnecting them from the spark plugs.