I agree about neon testers lighting up easily but I did see a video somewhere demonstrating weak spark using the Accu Spark testers. The culprit cylinder definitely had a dimmer flash than the other good cylinders had. Maybe being red instead of white light makes it more noticable. I sure wish I had bookmarked that video as I can’t find it now.
Removing the ground electrode altogether on the home made tester should work just as good as opening the gap. Yeah, I know the gaps aren’t opened up in this old photo but it was taken right after the build.
Another involuntary way I’ve found good spark is by accidently getting my paws too close to the spark plug of a running motor. With rubber spark plug boots or not, touching in this area will let you know what is good and what isn’t. This hands on method isn’t recommended for anyone with a pacemaker!
Just a heads up but beware of these proximity pencil style spark testers sold on Epay and other places. I gambled my money and lost. It never did work and I never did get refunded for it. Live and learn.
