How to Check the Coil on a Stihl FS 66
- 1). Place the weed trimmer face up on a level work bench.
- 2). Remove the air-filter cover. The cover is located on the right side of the engine, directly over the carburetor and is held in place by a twist screw. Slide the air filter out. If the air filter is dirty, replace it with a new one. If it is not dirty, reinstall the air filter. Reattach the air filter cover.
- 3). Remove the spark-plug wire from the spark plug located on top of the engine. Plug in one side of the spark tester into the spark-plug wire that was just removed. Plug in the other side of the spark tester into the spark plug.
- 4). Pull the starting coil rapidly while watching the spark tester; if there's a strong blue spark, the coil is fine. If the spark is weak or non existent, the coil needs replacing.
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