Diagnose engine problems instantly with this essential CNBJ in-Line Spark Plug Tester. Simply connect between spark plug and wire to see if spark is present. The nickel-plated shaft with 6" boot/cable and 5" light housing provides reliable results for all engines from lawnmowers to cars. When your engine won't start, this fool-proof 6-12V diagnostic tool immediately tells you if ignition is the issue, saving you time and frustration on unnecessary repairs.