**Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.**
Most people check for proper engine spark by removing the spark plug, attaching the plug wire and grounding the plug to the engine while spinning the engine over and looking for a spark to jump across the spark plug gap. This method is not always reliable. The amount of voltage needed to jump the spark gap set at .030″ with the plug removed from the engine is about 2000 volts. The amount of voltage required to jump the same plug gap with the plug installed in the engine and operating under operating conditions is about 8000 volts, so it is possible to see a spark with the plug removed, but not have a spark with the plug installed.
A more reliable method is to remove the spark plug wire cap, and hold the spark plug wire approximately 3/16″ away from the spark plug and spin the engine over. A good ignition system will produce a orange/blue spark from the end of the spark plug wire to the spark plug. The problem with this method is it is easy to get shocked and hard to turn the engine over while trying to hold the end of the plug wire 3/16″ away from the plug. The benefit of this method is it is more reliable then the first method and doesn’t require purchasing any special tools.
Another method for checking the ignition for proper spark is to purchase the Briggs & Stratton Spark Tester, part #19368. This tool can be used to check for spark with the plug removed and using no hands, so the engine is easy to spin over and there is no risk of being shocked. The tool can also be used to view the spark while the engine is running. This is very valuable when trying to diagnose a rough running engine or a engine with intermittent problems.
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