The 10 Best Spark Testers

We spent 26 hours on research, videography, and editing, to review the top options for this wiki. If you’re afraid your spark plugs are on their way out — and you don’t want to risk getting zapped while using a screwdriver to check them — then one of these inline testers is just what you need. They can help you identify a multitude of ignition problems, saving you the hassle of having to take your car into the shop (not to mention hundreds of dollars’ worth of diagnostics). When users buy our independently chosen editorial picks, we may earn commissions to support our work.

10. Oregon 42-087

The Oregon 42-087 is a nifty, no-frills little tool that makes it easy to quickly diagnose ignition problems on just about any kind of motor. Be careful when using it, though — it’s designed with exposed metal parts that can give you a little jolt if you touch them.


  • Works well on lawnmowers
  • Instructions are poor quality
  • Glass viewing window often falls off















Brand Oregon
Model 42-087
Weight 2.7 ounces
Rating 5.0 / 5.0

9. GearWrench 2756D

It might not look like much, but the GearWrench 2756D makes checking your plugs incredibly easy. While other systems require you to identify the color of your sparks to learn the problem with your vehicle, this tool only sparks if the component is good — simple as that.


  • Spark is clearly visible
  • Doesn’t offer much room to maneuver
  • Not a very long-lasting option















Brand GearWrench
Model 2756
Weight 0.2 ounces
Rating 3.8 / 5.0

8. Performance Tool W84600

Admit it — you jump a little bit every time your tester makes sparks fly. If that’s the case, then the Performance Tool W84600 is right up your alley, as it’s designed to prevent sparks from shooting out to your ground, enabling you to check your plugs in safety.


  • Thick rubber insulation
  • Includes remote starter button
  • Plastic is prone to melting















Brand Performance Tool
Model W84600
Weight 0.8 ounces
Rating 4.2 / 5.0

7. Tool Aid 36350

Every serious mechanic needs to have the Tool Aid 36350 stashed in their garage. It has eight separate noid lights, so regardless of what layout your fuel distribution system is in, you should be able to check it with ease and have your car up and running in no time.


  • Long tube for deep plugs
  • Great for examining injectors
  • Difficult to swap out adapters















Brand Tool Aid
Model 36350
Weight 1.8 pounds
Rating 4.0 / 5.0

6. Thexton THE404

The alligator clip on the end of the Thexton THE404 holds it securely to your ground, so you don’t have to worry about accidentally brushing against it and sending it clattering to the floor. That also makes it easy to set it up in a convenient spot while testing.


  • Comes with safety shield
  • Helpful for improving spark quality
  • Probe is fairly short















Brand Thexton
Model THE404
Weight 0.8 ounces
Rating 4.1 / 5.0

5. Lisle 20700

The Lisle 20700 is the best solution we’ve found for testing unresponsive coil-on plugs. It makes it easy to check the distance on your gaps as well, thanks to the high-visibility white lettering that measures everything from 0 to 40k.


  • Round knob for simple gap adjustment
  • Ideal for use on motorcycles
  • Spark hard to see from far away















Brand Lisle
Model 20700
Weight 0.3 ounces
Rating 4.3 / 5.0

4. OTC 6589

For those who are rough on their equipment, there’s the OTC 6589. It’s made of a mixture of durable metal and porcelain components— no flimsy plastic pieces here — so it will last for years, provided you don’t drop it on hard cement.


  • Includes lifetime warranty
  • Minimizes risk of getting shocked
  • Designed for high-energy systems















Brand OTC
Model 6589
Weight 1.6 ounces
Rating 3.9 / 5.0

3. Tool Aid 23970

If you’re dealing with an engine with recessed plugs, then the Tool Aid 23970 is a must-have piece of equipment. Rather than forcing you to squint in order to see a faint spark, it uses a flashing bulb to let you know if there are any ignition or fuel delivery problems.


  • Also works with conventional systems
  • Can help diagnose electrical issues
  • Ideal for use in low light















Brand Tool Aid
Model 23970
Weight 8 ounces
Rating 5.0 / 5.0

2. Ram-Pro Diagnostic Detector

While it’s inexpensive, the Ram-Pro Diagnostic Detector nevertheless offers the kind of performance and ease-of-use you’d expect from a much more costly tool. At just six inches long, it’s easy to stash in a toolbox without having it constantly getting in your way.


  • Replaceable internal bulb
  • Flash is clearly visible
  • Formidable protection shield















Brand Ram-Pro
Model 2331
Weight 3.2 ounces
Rating 4.9 / 5.0

1. Lisle 20610

The Lisle 20610 boasts a nifty design that makes it easy to use even in cramped spaces, as it manages to offer you both a straight boot as well as a 90-degree-angled one on the same tool, making it an extremely versatile piece of diagnostic equipment.


  • Ideal for intermittent faults
  • Works well on boat motors
  • Easy to use by yourself















Brand Lisle
Model 20610
Weight 3.2 ounces
Rating 5.0 / 5.0