The 10 Best Spark Testers

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This wiki has been updated 18 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 recommendations, we may earn commissions to help fund the Wiki.

1. OTC 6589

2. Lisle 20610

3. OTC 3634

Editor's Notes

March 17, 2021:

As complicated as cars get, most still run exclusively on fuel, air, and spark. Many of these spark checkers, or ones very, very similar to them, have made the rounds in amateur and pro toolboxes for years. They're not terribly expensive, although there are a few different styles. The primary difference between them all is their shape and size, which can affect exactly which vehicles they work with.

The major changes we made this time around include the removal of the ABN Automotive 4269 due to reliability and availability issues. In its place came the Tool Aid 36350, which is costly, but allows home and working mechanics to use it easily on almost any make or model of vehicle. Otherwise, all our choices remain the same.

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.

4. Tool Aid 36350

5. Ram-Pro Diagnostic Detector

6. Tool Aid 23970

7. Thexton THE404

8. Lisle 20700

9. GearWrench 2756D

10. Oregon 42-087

Christopher Thomas
Last updated by Christopher Thomas

Building PCs, remodeling, and cooking since he was young, quasi-renowned trumpeter Christopher Thomas traveled the USA performing at and organizing shows from an early age. His work experiences led him to open a catering company, eventually becoming a sous chef in several fine LA restaurants. He enjoys all sorts of barely necessary gadgets, specialty computing, cutting-edge video games, and modern social policy. He has given talks on debunking pseudoscience, the Dunning-Kruger effect, culinary technique, and traveling. After two decades of product and market research, Chris has a keen sense of what people want to know and how to explain it clearly. He delights in parsing complex subjects for anyone who will listen -- because teaching is the best way to ensure that you understand things yourself.

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