Adjustable Car Ignition Coil Tester Ignition Spark Diagnostic Tool. Simple Car Spark Plug Tester Detector Ignition Plug Tester Tool. Car Adjustable Ignition Coil Tester Ignition Spark Test Tool. Turn the key switch 4 clock-wise to turn on tester,indicator 3 will light up, tester is now working at 1000rpm/min.