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coils issues

Discuss fixes, upgrades and modifications to your M37

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Re: coils issues

Postby carolinamv » Sun Jul 24, 2016 3:06 pm

I pulled all mine apart today and made sure they were clean, air flowed through fine, so I guess I'm good on that
-Jay

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Re: coils issues

Postby ZGjethro » Sun Jul 24, 2016 5:43 pm

I have all the right fittings and vent lines. It seems like a pretty good passive system, with no moving parts. I have to wonder how much air goes through those lines though. Inside the distributor, the fittings have pretty small orifices. I would think a small electric air pump would do a much better job of moving more air, but that would be an added expense and complexity
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Re: coils issues

Postby ZGjethro » Mon Jul 25, 2016 8:00 pm

New coil, cap and rotor are in. Distributor plopped right in and the plug wires were an easy hook up. I bought a 3/4" socket and an extension and welded them together to make a spark plug wrench. I think this is the first time the wires on the Distributor have been snug! Truck fired right up and runs great. I advanced the timing to 12 degrees btdc from 10 degrees, and I'm pulling the neighborhood hill in 3rd with more authority. I am at 8000' elevation.
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Re: coils issues

Postby carolinamv » Tue Jul 26, 2016 2:22 pm

Glad to hear shes running good,
-Jay

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Re: coils issues

Postby tumblwd » Sat Sep 23, 2017 9:23 am

I have read a lot of information having to do with the recommendation to test the coil when faced with an ignition/timing problem. I would like to test my coil(s) but do not know how. I have a small multi-meter. Can anyone explain how to test the coil, please?
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Re: coils issues

Postby just me » Sat Sep 23, 2017 12:32 pm

I have the autolite manual at home. I'll check tonight, but my factory could are 3 ohm and the Chinese knock offs are 6 ohm.
The filter is an RC network of capacitors and a resistor. I have the schematics in the radio noise suppression TM.
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Re: coils issues

Postby ez8 » Sun Sep 24, 2017 5:48 am

tumblwd wrote:I have read a lot of information having to do with the recommendation to test the coil when faced with an ignition/timing problem. I would like to test my coil(s) but do not know how. I have a small multi-meter. Can anyone explain how to test the coil, please?


On the first page of this thread a user by the name "Carter" has a link to an image that shows the different test areas and the desirable results. Follow that and you'll be golden.
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Re: coils issues

Postby tumblwd » Sun Sep 24, 2017 1:00 pm

ez8, Thank you for your reply.
I tested 3 coils, first in the truck with the ignition switch on, then on the bench, out of the distributor. The results were the same in both instances. Here are the results:
Coil #1 (chrome unit, recently purchased from VPW):
Primary (A to B as in the diagram posted by Carter on page 1 of this thread) 11.6 ohms (on 200 ohm setting)
Secondary (C to Ground or, in the case of the bench test, to B) 10.5 Mohms (on 20,000 ohm setting).
Coil #2 (chrome unit, in the truck when I bought it - suspect overheating several times):
Primary 11.7 ohms
Secondary 10.55 Mohms.
Coil #3 (used Autolite unit from extra used motor that came with the 1954 M37):
Primary 11.8 ohms
Secondary 10.6 Mohms.
Although the values are similar to what ZGjethro reported, I still have no idea if they are good or not.
I installed coil #3 in the truck and got nothing - no spark.
I installed coil#1 in the truck and now, as I crank the engine, I get no spark, weak spark, no spark, strong spark, then no spark for as long as I continue cranking.
I also exchanged the condenser (capacitor) and rotor that came with the truck for new ones.
No difference.
My next step will be to install a new distributor cap. After that, new spark plugs. After that, maybe a pound of C-4 (kidding !)
Any thoughts and suggestions welcome.
I am next going to update my original post "Help! My truck won"t run!"
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Re: coils issues

Postby ez8 » Sun Sep 24, 2017 1:29 pm

I also am using a chrome coil from VPW and have had no problems with it as of this moment. For the time being, let's assume this one is good. Leave it in the truck.

New capacitor and rotor is a good step as well. You're on the right track with the new cap - my original one was actually hairline cracked and I didn't notice it until I took it completely out of the distributor and it began to fall apart. I got a new one from VPW and have had no issues. I'd say go ahead and also order some new spark plugs while you're shopping. You can't get the Autolite 2243 or 2245 anymore so you should snap up a set of spares "for insurance" as long as your wallet will let you. You can get them for about $90.00 shipped from saturnsurplus on e-bay.

Also be sure to check your plug wires and the wire that goes from the wiring harness to the distributor for continuity. I added some dielectric grease to the spark plug wire connections as well.

If all of that checks out, you might look at the suppression filter in the distributor (where the current comes in from the wiring harness). I've read on this board that if that filter goes bad, it manifests itself with symptoms similar to bad ignition.

Ignition is a pain in the butt on the M-37 because of the waterproof system, but once you get everything dialed in she'll kick right over every time.
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Re: coils issues

Postby tumblwd » Sun Sep 24, 2017 6:19 pm

Thanks ez8. Your comments and suggestions much appreciated.
I will go back at it tomorrow and let you know how it turns out.
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Re: coils issues

Postby rickf » Mon Sep 25, 2017 4:20 pm

Original NOS coils were 5-7 ohms primary and 11-14K ohms secondary. When the chromies started coming out with the measurements you get everyone said they were all bad BUT, they are working so there must be something to it. The problem is when the primary burns and you end up with an open. It starts out with intermittent failure when hot, and progressively gets worse. It will usually restart when cooled off but will run less time each time. The input capacitor is a biggie anymore. I never used to see them going bad but I am seeing a lot more of it now. probably due to age, they are drying out and shorting. They can be bypassed with no harm, all they are there for is radio suppression. I have taken them and cut away all of the capacitor part inside and soldered a wire to the terminal that comes out and attaches to the wire from the harness. That way it looks totally stock. The soldered on wire inside will go to the coils just as before.
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1964 M151A1
1967 M416
1984 M1008
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12/1952 M100 gone
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Re: coils issues

Postby tumblwd » Thu Sep 28, 2017 1:02 pm

Thanks rickf and ez8.
I installed new plugs and changed the rotor yesterday and I got some spark but no start yesterday. I thought I might have flooded the engine in my enthusiasm so I waited until today to try again. This time, after a few stumbles, it started!

And blew heavy grey/black smoke so thick I could not see. The motor sounded good, running at slightly more than idle, but it slowed and stalled after running for a couple of minutes.

For pics and the rest of the story, please see my latest post on "Help! My truck won't run!"
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Re: coils issues

Postby Stovebolt » Sat Sep 30, 2017 12:32 pm

Thanks for the info in this thread. All Summer, the truck has been having the issue described by others in these coil threads -- runs pretty goo0d for 10-15 minutes then cuts off and won't run again until it's sat for 5-10 minutes or so. So I just checked the coil: Cool I got 15 ohms on the primary and 16.3k on the secondary. Hot (I ran the heat gun on the coil) I got 17.2 ohms on the primary and off scale on the secondary.

Time for a new coil? Does it matter that I've installed the Pertronix kit?

Thanks,
John
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Re: coils issues

Postby rickf » Sat Sep 30, 2017 5:19 pm

No, The Pertronix is just the trigger for the coil.
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Re: coils issues

Postby Stovebolt » Mon Oct 02, 2017 3:12 am

Bad coil then?
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