Inline Spark Plug Tester Engine Ignition Tester Straight Boot Ignition Tester Light Lawnmower Engine Checker Armature Diagnostic Detector for Automotive Car Lawnmower Internal External Engine (1). Simple and convenient operation: it takes about 30 seconds essential for trouble shooting all internal combustion engines, you just need to simply connect the tester between the spark plug and the plug wire, if spark is being sent, the tester will mirror the spark and light up, to find dirty spark plugs, defective points, bad cables or connections, etc.
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