Your Spark Plug is Telling You Something...and it Never Lies

If it is necessary to remove the spark plug from your small engine, always do so when the engine is cool. Wipe away and clean the area near the spark plug hole to prevent dirt and debris from falling into the cylinder. Always use the correct size spark plug socket (it is deeper, and has a rubber insert inside).

Although some plugs may be stubborn on removal, always be sensible to protect the threads of the spark plug hole. When removing a stuck plug, if necessary, remove one full turn, then tighten half turn before removing fully.

Once removed, it can be inspected and can provide clues as to the overall health of the machine.

Fuel Fouling-Fluffy, dry black deposits near the electrode end

Oil Fouling-Caked on lumpy deposits near the electrode end

Overheated plug-Excessively white, dusted appearance

All of these appearances point to different issues and can provide insightful clues during a troubleshooting process.

Without getting into too much detail about spark plug components, on the threaded portion of a the plug there is whats called an electrode. The tiny air space between the second electrode that runs down the entire length of the plug is whats called the "gap".

If either oil fouling or fuel fouling is occurring, the carbon or oil deposits can become so severe that the gap on the plug becomes completely blocked.

Spark plugs can provide insightful clues about your engine!

The gaps on spark plugs can be adjusted using a special gapping tool. Follow instructions on the use of the gapping tool, provided by the manufacturer. Set the gap required for your engine model; never assume the gap is correct, and always check the gap of new spark plugs. The gap specifications will be located in your engine's service information.

With the spark plug removed, you can also inspect the electrode on the threaded side of the plug. Does it appear squared or rounded? A rounded electrode indicates it is worn and must be replaced.

In a previous post we mentioned the importance of ensuring your using the correct spark plug for your engine. An important thing to consider is that there are numerous spark plug manufacturers. A part number of one spark plug manufacturer can be cross-referenced to another manufacturer with a different part number. However, both spark plugs would be compatible with the engine, assuming the original spark plug cross-referenced is indeed the correct plug.

By using a reputable online spark plug cross-referencing catalogue, you can determine which spark plug part number of a different manufacturer, matches the required spark plug used in your engine. This allows flexibility in choosing which brand you'd prefer to install.

When reinstalling, thread in properly by hand first to prevent cross-threading and once properly started by hand, tighten to specified torque using appropriate ratchet, do not overly tighten!

Never the Norm!