Thexton THE404 Spark Tester

And actually it works better than my last one. The gap markings are clearly marked and was able to test coils as per warranty standards just fine. The glass tube makes the spark extremely visible for recording / photo purposes. Alligator clip is strong, I usually clip it to an ear of the engine block or alternator mount or something. No issues with grounding out the coils and is exactly what you pay for. Size is about the same as an ordinary spark plug. I have two of these in my box and haven't managed to break them yet. Definitely worth it.

I used these style spark plug testers at school. they are EXCELLENT! You can adjust how big you want your spark to be, which easily helps you determine if your coil packs or distributors are getting enough voltage or if your spark plug is bad. Long story short on how to use this tool: You unplug your coil/spark plug wire (depending on the type of ignition system of course) and connect it to the end of the tester that looks like the top of a spark plug. The piece that has an alligator clip just clips onto any part of the car that is metal in order to create a ground. Once it's hooked up, start your car. If you're able to get an arc going across the points in the tester, especially when it's adjusted all the way out, then you know your coils/distributor is getting plenty of voltage so it is good, and is most likely your spark plugs. If you barely get any spark, especially when the tips are almost touching then you're not getting enough voltage for some reason, which indicates a bad distributor/coil packs, or bad wiring somewhere between the coil packs/spark plug wires and the positive battery terminal. This tool is an excellent little diagnostic tool to have, and I recommend that every mechanic should own one! This is a great tool to help fix misfires and other ignition issues!

A must have for every garage

Works great

Good quality tool.

I was working on a mower that was run out of oil and had a brake on the engine dragging. I was almost sure I had a bad coil. I used the spark plug grounded on the engine to check the coil but I must have had a bad ground. I saw this on Amazon and say that you could adjusted it for each engine you were working on and ordered it up. it came in a few day and I tried it on the mower with what I though was a bad coil. I hooked it up and had my wife give it a pull and BINGO I had a good blue spark. I had a hard time seeing the spark at first in a well lite garage but turning off a few light and you can see the blue spark. for $15 including shipping it a great tool for small engines to check for spark. before this one I had a tester with a small light bulb in but it didn't work very well and I don't think the bulb grounded well on the inside of the tester. So if you tinker with small engines buy one these testers well worth the $15.

A must have for troubleshooting vehicles with high energy ignition systems. It provides a very simple way to test your spark plug coil packs. This spark tester is easy to use. I like the ability to adjust the spark gap to match the system that I am working on. The spark is easy to see when the ignition system is working properly.

I got this to spark test my Honda 4 stroke 30hp outboard. The plug boots on the engine are too small to fit this. So I can’t speak to any other features, just be aware that it may not fit your application. Electrode tip is 6mm/0.23” in diameter so measure your boot first before buying.