Draper - In-Line Ignition Spark Tester. Diagnose faults quickly and accurately with this hands-free ignition spark tester. New to the Draper range, it features a 57mm probe length and 43mm clear inspection tool that instantly shows whether a spark is present. The In-Line Ignition Spark Tester clips easily into place and is a must-have tool for professionals who repair vehicles and petrol or power operated tools, such as trimmers, chainsaws, and lawnmowers.