Check The Spark Plug

Disconnected, dirty or fouled spark plugs are common causes for engines that won’t start. Spark plugstypically need to be replaced every season or 25 hours of use. You should also check that the spark plug gap is set properly.


If your spark plugs look good, problems with your ignition system can also preventing a spark. These can range from a faulty spark plug lead, shorted kill switch or flywheel key damage.

To test and fix, check out our Small Engine Ignition Systems FAQ or reach out to your local Briggs & Stratton dealer for advanced repair help. Learning how to check, clean and change a spark plug is a valuable part of your DIY education.

Whether you’re doing regular maintenance or troubleshooting why your lawn mower or small engine won’t start, this 3-step guide will provide the resources you need to keep your machine running right! 

The electrodes on a spark plug must be clean and sharp to produce the powerful spark required for ignition. The more worn or dirty spark plugs are, the more voltage – and the greater the tug on the rewind – required to produce an adequate spark.

If you haven’t tuned your engine recently, your mower won’t start and/or you have to tug repeatedly on the rewind to start the engine, a damaged spark plug may be the culprit.

These problems may also cause excessive fuel consumption, deposits on the cylinder head and oil dilution. Luckily, spark plugs are one of the easiest engine components to repair and an inexpensive one to replace.

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