Ignition Coil Resistance Test

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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armybuck041
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Ignition Coil Resistance Test

Post by armybuck041 » Thu Aug 27, 2009 6:35 pm

Hello,

I need a favour from someone.

I have 4 Ignition Coils in varying states. Rather than dropping another $50 for a new one, i'm wondering if someone could do a resistance test on a NOS USGI Ignition Coil and Post up the specs so I can check these ones.

The instructions are here:

http://autorepair.about.com/od/troubles ... st-ohm.htm" onclick="window.open(this.href);return false;

The reason I ask for this is that every Website I have looked at showed different specs for what the resistance should be, or tell yoy to check the shop manual. Unfortunately, all the TM's i've looked at don't show the Resistance Specs for the Ignition Coil.

My "good" one has 4 Ohms Primary and 14,000 Ohms Secondary. Acoording to some sites, its OK, others, its junk.

Besides, i'm sure others will appreciate having the info.

Thanks

Scotty
Scott Bentley
3 x M151A2 CDN
SN 43813, CFR 74-09195, 1 Svc Bn (Restored as 74-09150, 4 CER)
SN 46065, CFR 74-09782, 422 Tac Hel (RIP)
SN 46693, CFR 74-09808, W Bty RCA (RIP)
Gone but never forgotten: Sgt Shane Stachnik, KIA on 3 Sept 06, Afghanistan


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Mr. Recovery
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Re: Ignition Coil Resistance Test

Post by Mr. Recovery » Thu Aug 27, 2009 7:08 pm

Hi, check out this link, should tell you what you need. :)
http://www.g838.org/viewtopic.php?f=3&t=1795" onclick="window.open(this.href);return false;

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Daniel J. Wroten
1963 Willys M151,
American Legion Post 275
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U.S. Army 1960 - 1966
Colorado Army Nt. Guard 1975 - 1980
Md. Air Nat. Guard (AGR active duty) 1981 - 1995

Rickf
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Re: Ignition Coil Resistance Test

Post by Rickf » Fri Aug 28, 2009 3:34 am

Hey Scotty, Check out my post about never leaving your cell phone home. That coil in the picture tested good even as it looked! It was bad believe me, the problem is when it cools off it will work for a bit and also test good. As Raymond had said on the G838, that oil is nasty stuff, Dioxin.


Rick
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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raymond
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Re: Ignition Coil Resistance Test

Post by raymond » Fri Aug 28, 2009 7:05 pm

Here is a link to where Ken aka Muttguru posted on the M38 page how to test a military 24 volt coil. If you buy any new coils, insist that they be U.S. made USGI coils with the part number printed on them. There have been some cheaper foreign made coils going around that are junk. I had one that exploded inside my distributor. That is a nasty job to clean up.

http://www.g503.com/forums/viewtopic.php?f=105&t=141199" onclick="window.open(this.href);return false;

Also be careful with any automotive coil made pre 1977 as it could potentially contain PCB (polychlorinated biphenyl) in the dielectric oil. Not all do though. If the oil was sourced from Shell, it is safe, as Shell's dielectric oils have never contained PCBs. PCBs are carcinogenic and cause several types of cancers, and their effect is cumulative, so stay away from them. While PCBs are not dioxin, they can form dioxin when you burn them. They must be burned at high temperatures. While the amount of oil in any one coil is low, and the amount of PCB potentially in any pre 1977 coil is also low, it does not mean you should not be careful. Here is a link to some pictures of what happened to a coil that Rick had go bad.

http://www.g838.org/viewtopic.php?f=2&t=2014" onclick="window.open(this.href);return false;


Raymond
"On the day when crime puts on the apparel of innocence, through a curious reversal peculiar to our age, it is innocence that is called on to justify itself." Albert Camus

armybuck041
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Re: Ignition Coil Resistance Test

Post by armybuck041 » Sat Aug 29, 2009 6:44 pm

Rickf wrote:Hey Scotty, Check out my post about never leaving your cell phone home. That coil in the picture tested good even as it looked! It was bad believe me, the problem is when it cools off it will work for a bit and also test good. As Raymond had said on the G838, that oil is nasty stuff, Dioxin.


Rick
Had the same thing happen to the Coil in my Brand New NOS Distributor. Puked out its oil. Found it strange as the Distributor was a very late production and I only put 200 miles on it.

I just checked it, low and behold, the Resistance was still pretty much within spec. So as stated, the Resistance Test is only one check, but not a definitive test for determining if the Coil is good.

On the bright side, the Ebay seller that sold me the "Chrome" non-functioning Coil is going to send me a USGI Coil out of one of his Government Rebuilt Distributors.

I guess my last question is, are these things that bad, or did I just get unlucky. I will definately be keeping a spare on hand in future.

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Re: Ignition Coil Resistance Test

Post by Rickf » Sun Aug 30, 2009 5:17 am

I just got two of the chromies ad I will see what happens. I am toying with the idea of adding a resister inline to drop the incoming voltage to 20 volts which will substantially drop the temperature of the coil in operation. I know a guy who has been running a mutt engine in a buggy for quite a while on 12 volts with a 24 volt coil and it runs fine so obviously you still get a hot enough spark. I figure if I drop it fro 28 volts running to 20 volts I can savethe coils from cooking.


Rick
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

armybuck041
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Re: Ignition Coil Resistance Test

Post by armybuck041 » Sun Aug 30, 2009 6:03 am

Rickf wrote:I just got two of the chromies ad I will see what happens. I am toying with the idea of adding a resister inline to drop the incoming voltage to 20 volts which will substantially drop the temperature of the coil in operation. I know a guy who has been running a mutt engine in a buggy for quite a while on 12 volts with a 24 volt coil and it runs fine so obviously you still get a hot enough spark. I figure if I drop it fro 28 volts running to 20 volts I can savethe coils from cooking.
Rick
That would be interesting and makes alot of sence. In my opinion the Ignition Coils are the biggest wild card with these things. Once I got my Fuel System straightened out and Carb cleaned and properly adjusted, the only recurring issue seems to be ignition.

j3cub
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Re: Ignition Coil Resistance Test

Post by j3cub » Sat Sep 18, 2021 7:01 am

I just purchased a chrome unmarked coil on @mazon $53 delivered and it tested 12 Ohms on primary and 12k on secondary. going to install it now and see if it works!

j3cub
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Re: Ignition Coil Resistance Test

Post by j3cub » Sat Sep 18, 2021 1:41 pm

Success! Started up 1st try. Now to see how long this one is good for.

Rickf
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Re: Ignition Coil Resistance Test

Post by Rickf » Sat Sep 18, 2021 5:00 pm

It is a Chinese special so keep spares with you at all times. I have had them last a year and I have had them last a day. One of our members had one blow up, literally, on the first start.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone


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