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How to make one

This page will show you how to make an ignition spark tester for testing the ignition spark on your lawn and garden power equipment. It's important to remember that checking spark with a standard spark plug only tells you that the ignition is producing "some" spark. To find if your ignition system is producing a strong, quality spark that will fire the spark plug under compression, you need something different, a tester that will simulate the conditions the spark plug operates under. This is an easily made tool that most home "do-it-yourselfers" can make themselves.

CAUTION; This tester will produce an open spark. Use caution when using. Move tester as far from the spark plug hole as possible to avoid igniting any fuel spit out the hole. Make certain no spilled fuel is left on the equipment or otherwise near the test area.

A good plug to use in making this tester is the Nippondenso W14-U. It's full size assures that it can be connected to any plug wire and boot size. In addition the wire terminal of the plug unscrews leaving a threaded extention which works for some older Honda and other Japanese wire terminals. Any plug without an extended center electrode should work in most cases but this plug style provides good versatility.

Take the plug of your choosing and start off by clipping the grounding wire. Use caution as the clipped wire may go shooting off. Safety glasses here would be a good idea.

This is how it will look. Notice how any spark will now need to jump from the center electrode to the outer rim.

Next remove the insulation from an alligator clip and flatten and shape the area that was meant for a wire connection. Shape to fit the round metal base of the spark plug and solder the clip on.

Connect the tester to the plug wire and clip to the head and pull the rope. As you can see, a bright spark is easily visable if in the shade. You'll also hear a sharp snap.

This is another view of the tester in action but not as close up.

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