Holding the spark plug wire with your pliers, touch the threaded portion of the spark plug to the grounding point. Have somebody crank the engine with the key, and look for a bright blue spark to jump across the spark plug gap. If you see a nice, bright spark (clearly visible in daylight) your coil is doing its job.
Testing an Ignition Coil on the Car
By Matthew Wright, About.com Guide
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Test the Coil for Spark
If you see a spark, the coil is doing its job.
photo by Matt Wright, 2008
Holding the plug wire with insulated pliers, find a spot on the engine that is a good and easily accessible grounding point. Pretty much any exposed metal, including the engine itself, will do.
Another Coil Test
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