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steve(ill) 
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Joined: 11 Sep 2009
Location: illinois
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 Topic: a coil with no resistance ??
Posted: 12 Oct 2024 at 3:25pm |
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Gots a 1990 Briggs horizontal opposed 2 cylinder 18 HP tractor.. Just rebuilt the motor after setting for several years.. Had a bad miss fire after 45 minutes and not revving up. Was going to rebuild the carb ( which i did today with good success), but though i would check for SPARK as that is simple. This has a pickup coil on the side of the flywheel so dont need a battery for ignition ( i think).... anyway, i pulled the plugs and rotated engine and had spark at both plugs... I then took my ohm meter and set for 20K and measured the plug wire to ground... NOTHING.. open circuit.. I then check the KILL wire to ground ( suppose to be a couple ohms.. and NOTHING.. open circuit...touch the meter leads together and get ZERO--OK.. I know the meter is good and i have been using one for 60 years .... Not sure how that can happen... never seen that before !
Edited by steve(ill) - 12 Oct 2024 at 3:27pm
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DMiller
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Joined: 14 Sep 2009
Location: Hermann, Mo
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Posted: 12 Oct 2024 at 3:46pm |
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Points open?
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Ken Mn
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Joined: 10 Nov 2021
Location: Zumbrota Mn.
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Posted: 12 Oct 2024 at 4:14pm |
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Try measuring the resistance from one plug wire to the other. I have a magneto for a Wisconsin motor that fires both plugs at the same time. The coil winding is not connected to ground. The Briggs may be the same.
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steve(ill)
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Location: illinois
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Posted: 12 Oct 2024 at 4:42pm |
I will try that next week Ken.. never heard of that before..no mention of anything like that on the INTERNET............. NO there are no points... some type of IMPULSE coil that just fires as the crank magnet comes around each time... imnot sure how that works.. no point, no CDI box... just that double coil and flywheel.
I worked on a weed eater and leaf blower motors last year.. they didnt have a point either.. Similar i guess... ( but they did have resistance readings !!)
Edited by steve(ill) - 12 Oct 2024 at 4:44pm
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Like them all, but love the "B"s.
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steve(ill)
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Location: illinois
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Posted: 12 Oct 2024 at 4:50pm |
from BRIGGS----
When you start your lawn mower or small engine, you turn the flywheel and its magnets pass the coil (or armature). This creates a spark. The ignition system coordinates the timing so that the spark will ignite the air-fuel mixture in the combustion chamber just as it reaches maximum compression in each engine cycle- thus, maximizing the engine’s power. Once the engine is running, the flywheel keeps rotating, the magnets keep passing the coil and the spark plug keep firing based on a specific timing. Types of Ignition Systems - Solid-state systems: the more modern option, these systems use a tiny transistor in the coil or armature to close the electrical circuit that travels through the spark plug lead to the spark plug(s).
- Breaker point systems: used on engines made before 1980, these systems use a mechanical switch instead of a transistor to close the electrical circuit used to produce a spark.
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Like them all, but love the "B"s.
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LouSWPA
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Joined: 11 Sep 2009
Location: Clinton, Pa
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Posted: 15 Oct 2024 at 1:45pm |
 steve(ill) wrote:
Gots a 1990 Briggs horizontal opposed 2 cylinder 18 HP tractor.. Just rebuilt the motor after setting for several years.. Had a bad miss fire after 45 minutes and not revving up. Was going to rebuild the carb ( which i did today with good success), but though i would check for SPARK as that is simple. This has a pickup coil on the side of the flywheel so dont need a battery for ignition ( i think).... anyway, i pulled the plugs and rotated engine and had spark at both plugs... I then took my ohm meter and set for 20K and measured the plug wire to ground... NOTHING.. open circuit.. I then check the KILL wire to ground ( suppose to be a couple ohms.. and NOTHING.. open circuit...touch the meter leads together and get ZERO--OK.. I know the meter is good and i have been using one for 60 years .... Not sure how that can happen... never seen that before !
I still suspect the meter! you have spark, but cannot read resistance on the coil, cannot read resistance on plug wire. Me thinks you have a funky meter, OR more likely, funky meter leads |
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I am still confident of this;
I will see the goodness of the Lord in the land of the living.
Wait for the Lord;
be strong and take heart and wait for the Lord. Ps 27
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
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Posted: 10 Nov 2024 at 8:30am |
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Well, i finally got back around the checking the COIL RESISTANCE...Ken was right. Each wire measures OPEN to ground, but i have CONTINUITY between the two coil wires. Never heard of that before.. I was thinking of changing out the coil this winter ( got to pull the motor out)... but KEN saved the day!! .... Now i know why i had NO RESISTANCE !
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Like them all, but love the "B"s.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
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Posted: 10 Nov 2024 at 4:31pm |
steve(ill) wrote:
Well, i finally got back around the checking the COIL RESISTANCE...Ken was right. Each wire measures OPEN to ground, but i have CONTINUITY between the two coil wires. Never heard of that before.. I was thinking of changing out the coil this winter ( got to pull the motor out)... but KEN saved the day!! .... Now i know why i had NO RESISTANCE ! |
Yup, Onan twins are the same; they fire both plugs at once. Quite a few modern automotive work this way too, they fire plugs in pairs. One of the low-budget hacks for bad Onan'$ coil$ is to use a GM coil.
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