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09-27-2023, 06:15 AM | #1 |
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Join Date: Jun 2023
Location: New Castle, PA
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Not all cylinders are firing when ignition is switched to the magneto.
I recently put a new mag post on my 1926 coupe. It didn't run when switched to the mag before, and because the internal pin on the old post was bent. It runs fine on the battery. So I guess the old post might not have been the problem. However, now it will only kind of run on the mag when the spark is advanced somewhat high. But not all the cylinders are firing when on the mag. My dad described it as "intermittent." What could be the problem here? Could it be something with the coils? They're brand new, purchased from Snyder's shortly after I bought the car back in April. It can't be the spark plugs, because they work fine on the battery. Is it something with the magneto itself?
Ok, people are telling me to check the magneto's output. What is the correct output? What would be considered "low" output? EDIT/UPDATE: I disconnected the wire from the mag post and tried to test the output with a meter. Unless I have a bad analog meter, there was NO OUTPUT, regardless of how the spark and gas levers were set. I also tested it with a compass by manually turning the engine over. The compass moved when the engine turned over, so there must be some sort of charge in there still. EDIT/UPDATE 2: I got in contact with the local model t club, the guy who replied to my email said that if it runs fine on the battery but bad on the mag, it sounds like the field coil assembly is dying. Last edited by George1348; 10-06-2023 at 05:59 AM. Reason: Updating post. |
09-27-2023, 06:58 AM | #2 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
Just because you purchased "new" coils, it's best to have them checked out for proper setting by a competent "coilman" such as Ron Patterson or Brent Mize.
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09-27-2023, 07:01 AM | #3 |
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Location: New Castle, PA
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Re: Not all cylinders are firing when ignition is switched to the magneto.
I'll contact the local club and see if they have a guy who can check them. And if they don't, I'll find someone to send them to.
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09-27-2023, 01:31 PM | #4 |
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Location: Oregon
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Re: Not all cylinders are firing when ignition is switched to the magneto.
You can check the mag output with a volt ohm meter. Check on the AC scale.
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09-27-2023, 02:22 PM | #5 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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09-27-2023, 02:51 PM | #6 |
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Location: San Antonio, Texas
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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The old headlight bulbs that worked off the magneto before they started installing starters and generators, were 24-volt bulbs but they could handle voltages up to 28-volts or more as long as it didn't get too high. Most folks drove slower at night so they wouldn't out run the headlights. |
09-27-2023, 05:30 PM | #7 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
make sure the coils are making solid contact in the coilbox. sometimes they will jiggle around and cause a misfire. Also make sure the engine will run smoothly with the battery before concentrating on magneto issues
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09-27-2023, 06:05 PM | #8 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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09-30-2023, 05:25 PM | #9 |
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Location: Rhinebeck, NY
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Re: Not all cylinders are firing when ignition is switched to the magneto.
Coils should be set at 1.5 -2 volts when vibrating with spark plug attatched.
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09-30-2023, 10:30 PM | #10 |
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Location: Noxon, MT
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Re: Not all cylinders are firing when ignition is switched to the magneto.
As stated check your magneto output voltage. Use a analog meter on AC. If it's low you can charge the magnets in the car. I used the method using a compass and three car batteries in series. It worked OK.
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10-01-2023, 06:01 AM | #11 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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10-01-2023, 11:13 AM | #12 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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10-01-2023, 11:37 AM | #13 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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10-01-2023, 01:04 PM | #14 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
If there is really no voltage from the magneto the coils will not buzz or do anything. Are you reading the AC scale?
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10-01-2023, 07:17 PM | #15 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
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10-01-2023, 07:50 PM | #16 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
I thought you had said it fired intermittently on mag. If so and now you have no voltage fdrom the mag during the test it may be a problem with the mag post.
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10-01-2023, 07:59 PM | #17 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
It did. My dad and I don't get it either. I will check the mag post tomorrow. It's brand new though, so I can't imagine there's something wrong with it, unless it somehow isn't seated properly.
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10-02-2023, 03:37 AM | #18 |
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Re: Not all cylinders are firing when ignition is switched to the magneto.
Sometimes fuzz from the band material will collect on the mag post and prevent current from reaching the magneto wire.
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