Ignition Analyzer?

[Buccaneer]

Is there any "old mechanic" tricks to a analyze
the ignition on a small engine, while it’s running?
I know "way back" for automobiles, they used
oscillioscopes, but not sure they ever were used
on outboards. I was thinking of something
more along the lines to measure voltage
differences between cylinders, but pretty sure
my VOM wouldn’t like 10,000 volts 😮

I’m guessing I have a bad coil in this HD-15 Johnson
as it’s running so "erratic"……
https://youtu.be/aPybyPCCht8
Lacking a Steven’s Tester or similar, and also
having no spare coil to try, I thought it
would be interesting to know if there’s any
other way to diagnose the problem.
Thanks!

Prepare to be boarded!

[Mumbles]

If you are sure it’s an electrical problem, I’d double check the Bakelite brush holders with a magnifying glass for any signs of voltage leaks or carbon tracks before condemning the coil. The HS-10 I was working on would run intermittently on two cylinders and then drop to one. I was starting to suspect a bad coil to but switching the internal parts around helped to figure out the problem. It was a tiny hole in one of the brush holders allowing the current to jump to ground thru one of the hold down screws.

Before I dug it out, the hole was almost invisible but I could see the carbon track after a good cleaning.

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[jerry-ahrens]

I see in your post that you don’t have a Stevens tester, but I would highly recommend one. I bought mine for $10 at a swap meet, then sent it back to Stevens to be overhauled. They have (at that time) an old retired employee that comes in a couple days a week to repair or refurbish these old machines. I thought I would only use mine for the antique outboard hobby, but I also use it on modern stuff at my boat shop. The nice part is that you can power test coils to see how they function under load, as well as an insulation leakage test… It will also test condensers. A very nice piece of equipment for the antique outboard mechanic

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[Buccaneer]

Mumbles, I remembered your post at the time when I had mine
apart, and didn’t notice anything that looked like it had been
arcing, but I guess it’s worth another look.

Jerry, if you want to sell me your Stevens and double your money,
I have the $20 🙂
I’m not sure how the Stevens hooks up when testing the coils,
but in the case of my HD-15 mag, would a hidden arcing problem
in the "grounding towers" (that has the carbon brushes) show up
during the test?
Thanks!

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Prepare to be boarded!

[frankr]

Most coil testers (even a buzz box) can be used along with a coil to produce spark voltages. The high voltage is then used to detect leakages such as that. Especially useful for testing distributor rotors if you ever get into that.

[Buccaneer]

I can remember my uncle, forty some years ago, testing
small engine / lawnmower coils by hooking up a car
battery to the primary terminal and working the points
manually, noting whether or not the spark plug would "spark",
but I’m a little / lot hesitant doing that with 77 year old
obsolete coil. 😮
Frank, what are you calling a "buzz box", and how would
one use it? Do you mean like a Model T Ford buzz box?
Thanks.

Prepare to be boarded!

[mr-asa]

I was told to get one of these a while back for my Mustang. However you have to realize that the color for a 2-stroke, or even modern ethanol gas will have a different burn color than the graph they give you.

https://www.youtube.com/watch?v=xEZ0-uN0NA4

[Buccaneer]

Interesting tool Mr. Aza, but looks most suited for carb adjusting,
instead of analyzing the ignition. My favorite tool "back in the day"
for tuning the carb on my car was the vacuum gauge.

Prepare to be boarded!

[frankr]

quote Buccaneer:

I can remember my uncle, forty some years ago, testing
small engine / lawnmower coils by hooking up a car
battery to the primary terminal and working the points
manually, noting whether or not the spark plug would “spark”,
but I’m a little / lot hesitant doing that with 77 year old
obsolete coil. 😮
Frank, what are you calling a “buzz box”, and how would
one use it? Do you mean like a Model T Ford buzz box?
Thanks.

Coil testers, in general speaking, do more or less what your uncle did. That is hook up a 6V battery to the coil and make and break the connection. The tester reads the amperage required through the primary to make it spark. So, with that little bit of information it is easy to dream up some way of doing that. Yes, a T Model works that way—I think. I’d have to refresh my memory on that. That was before my time.

Back in the day, we used an Eiseman coil tester that consisted of an electric motor with a cam on the shaft that opened and closed a set of regular automotive points. That make and break was sent to the coil primary. Stevens testers used a 6V car radio vibrator to provide the make and break. Merc-o-tronic, maybe the same, but I don’t know.

[billw]

I use one of these a lot and LOVE the thing. It works on anything with plug wires but not on modern, coil-over-plug systems. Once you get used to using it, you can tell whether a cylinder is fouled, rich or lean, besides whether it is just firing or not. I have made otherwise very good mechanics look like idiots in five minutes, with this thing.

http://buy1.snapon.com/products/diagnostics/dis.asp

Edit: Keep in mind, though, that it works only when an engine is running. It will NOT practically test for spark on a dead engine.

Long live American manufacturing!

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