Using a spark tester

[James Peck]

I read a nice article called “DIAGNOSING A WEAK IGNITION SYSTEM”. In the November/December 2022 Issue of Ageless Iron Almanac. This is published by Successful Farming, perhaps as an aid to drawing more SF subscribers.

 

I have in the past tested autos, tractors, and movers for spark by holding s spark plug with a gloved hand to ground and cranked it over. Sometimes I saw a spark. I eventually bought a Lisle spark tester without knowing exactly why I needed it. This has a spring clip to hold it to ground. With the other end of the Lisle tester connected to a spark plug wire, you can crank without holding the plug. What the article mentions, there is a slight possibility that I knew this previously, is that an ignition system can produce a spark in free air but not under compression. The tester helps simulate the compression load. The remainder of the article concerns using a DMM or VOM to check the coil. I only have DMMs now. If we remember, the Fordson Model F tractor produced in the Rouge location, shared a flywheel-based magneto system with the Model T Ford. Both certainly strike me as having been difficult to troubleshoot using the meters of the day

Edited December 5, 2022 by James Peck
lost a letter (see edit history)

[Akstraw]

I like the Lisle tester, too.

 

[Larry Schramm]

Here is the AC Spark Plug version.  They are the best for checking the single coil pack engines. I have three of them for testing the V6 GM engines.  Part # ST-125

 

Edited December 6, 2022 by Larry Schramm (see edit history)

[Larry Schramm]

And here is another style that you can use with the engine running.  Just place the grooved area against the plug wire and it will show if that plug is firing. Works well.  It was made by/for Champion Sparkplug Co.

 

Edited December 6, 2022 by Larry Schramm (see edit history)