How to Troubleshoot Bad Spark Plug Wire Symptoms

Spark plug wires deliver the electric spark your engine needs to ignite the fuel in the combustion chamber. When the spark plug wires die, so does your engine. Before replacing the spark plug wires, however, troubleshoot the wires with a voltmeter to make sure that they are the problem.

Things You'll Need

• Voltmeter

Instructions

1. Set your voltmeter to the "ohms" setting. On the dial, you should see a "Ω" symbol. This is the symbol for ohms, and will allow you to test the resistance of the plug wires.

2. Check one spark plug wire at a time. Remove the spark plug wire plug from the far right cylinder of your engine. Do this by pulling it straight out of the top of the engine. Nothing is holding it in place.

3. Follow the wire to the distributor end and pull the plug off of the distributor.

4. Place the black lead of the voltmeter into the distributor side of the plug. Place the red lead on the voltmeter into the engine side of the spark plug wire.

5. Turn on the voltmeter. The readout on the voltmeter should read "0" or near zero. The number may fluctuate slightly and this is OK. However, if the variance is more than .05, then the spark plug wire is faulty and must be replaced.

6. Re-install the spark plug when you are done testing it.

7. Repeat steps 2 through 6 for all spark plugs.

Tips & Warnings

• For specific information on removing your vehicle's spark plugs, consult the particular vehicle's manual (see Resources).

Resources

• Automobile Service Manuals