Spark Plug Wires

TESTING

NOTE: Only test one spark plug wire at a time. When the check is complete return the plug wire to its original location. If the wire is defective and more wires are to be checked, mark the wire as such, return it to its original location, then inspect the other wires. Once all of the wires are checked, replace the defective wires one at a time. This will avoid any mix-ups.

With Distributor

1. Remove the distributor cap from the distributor assembly.
2. Visually inspect the spark plug wires 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.
3. Inspect the spark plug wires to insure that they are firmly seated on the distributor cap.
4. Disconnect the spark plug wire thought to be defective at the spark plug.
5. Using an ohmmeter, measure the resistance between the distributor cap terminal and the spark plug terminal.

   NOTE: Make certain that a good connection exists between the distributor cap and the spark terminal. Never, under any circumstances, measure resistance by puncturing the spark plug wire.

6. If the measured resistance is less than 7000 ohms per foot of wire, the wire is good. If the measured resistance is greater than 7000 ohms per foot, the wire is defective and should be replaced.

Without Distributor

1. Visually inspect the spark plug wires for burns, cuts or breaks in the insulation. Check the spark plug boots and the nipples on the coil. Replace any damaged wiring.
2. Inspect the spark plug wires to insure that they are firmly seated on the coil pack.
3. Disconnect the spark plug wire thought to be defective at the spark plug.
4. Using an ohmmeter, measure the resistance between the coil terminal and the spark plug terminal.

   Fig. 2: Checking individual plug wire resistance with a digital ohmmeter

   NOTE: Never, under any circumstances, measure resistance by puncturing the spark plug wire.

5. If the measured resistance is less than 7000 ohms per foot of wire, the wire is good. If the measured resistance is greater than 7000 ohms per foot, the wire is defective and should be replaced.