The 10 Best Spark Testers
This wiki has been updated 10 times since it was first published in August of 2018. If you're afraid your spark plugs are not getting the current necessary to ignite the fuel in your engine, then one of these inline testers is just what you need. They can help identify a multitude of ignition problems without having to remove the plugs. Note that testing the electrical system of a car can be dangerous and should only be performed by trained automotive technicians. When users buy our independently chosen editorial picks, we may earn commissions to help fund the Wiki. Skip to the best spark tester on Amazon.
September 12, 2019:
Removed the Performance Tool 84800 because it is essentially a clone of the Lisle 20700. Removed the Tool Aid 36350 because it includes noid lights which are used to test injectors in the fuel system.
During a no-start problem with internal combustion engines, if the engine cranks at all, then the problem is narrowed down to either a fuel delivery issue, no spark in the combustion chamber, or a compression problem. Spark testers allow you to quickly determine whether the ignition system is the culprit. If there is plenty of spark, you can move on to diagnosing the other systems. If there is no spark, you can begin to run other tests to figure out which ignition component has failed.
Spark testers like the OTC 6589 are the most reliable and easy to use since you don't have to rely on specific connector styles, unlike inline models such as the Ram-Pro Diagnostic Detector which may not work on some cars and may light up even if the current is too weak to create an arc at the spark plug. We included the OTC 3634 because, even though it is actually just a test light, it can easily be used to test for spark.
Working on electrical systems is very dangerous and should only be done by trained technicians to avoid personal injury or damage to equipment.