Function - The spark plug ignition tester quickly diagnoses ignition and engine problems, including faults in the fuel system. It helps troubleshoot spark plug connections, contact points, defective cables, and related components that can cause misfire or loss of performance. Use - 1. Remove the spark plug cable when the engine is switched off. - 2. Attach the tester's black plug to the spark plug. - 3. Insert the metal end of the tester into the spark plug cable. - 4. Start the engine. The bulb flashes when the ignition circuit is closed. Application - Inline spark plug tester fits all 2- or 4-stroke engines and is essential for troubleshooting combustion engines. Suitable for cars, trucks, motorcycles, lawnmowers, chainsaws, trimmers, snow blowers, and other equipment. Durable - Internal bulb lasts for years; replaceable transparent housing design. The wires are well insulated, connectors fit securely, and the light is bright enough to be seen in daylight. Helps save diagnostic time. Use scenarios - Scenario 1: Diagnosing a car that stalls or misfires to identify ignition or spark-related causes. - Scenario 2: Troubleshooting a lawnmower or snow blower that loses power due to ignition issues. - Scenario 3: Verifying spark delivery after replacing ignition components or performing fuel system checks.