How To Tell if a Spark Plug is Bad


How To Tell if a Spark Plug is Bad

To check whether your spark plug has gone bad, you need to check your parts for the usual signs that it

may be fouled or damaged. Please review the following steps, which outline how to determine why the

spark plug is no longer functioning properly.


Step 1

Disconnect the spark plug wire. Clean the area around the spark plug to avoid debris in the combustion

chamber when removing the spark plug.

Step 2

Use the spark plug socket to remove the spark plug.

Step 3

Check whether there are very stubborn deposits on the spark plug, or whether there are cracked porcelain

or burned electrodes. If these conditions exist, replace the spark plug.

Step 4

Check the spark plug gap and adjust as necessary.

Step 5

If it seems to be working properly, replace the plug, being careful not to over-tighten (up to 15 feet pounds),

and then reconnect the spark plug wire.


If the engine tries to turn (even for a second) and dies, then you have a spark. This indicates that the problem

may be elsewhere (fuel, carburetor, valve, etc.). If the engine does not turn over at all, there may be a problem

with your ignition system. The first thing to do is to replace the spark plug.


See answers to frequently asked questions about troubleshooting ignition system problems to understand how

the spark tester recognizes problems with ignition coils, switches, flywheels or other small engine parts.


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