JD A no spark after warmed up

Clundgren · Nov 4, 2023

My 1950 JD A with Wico x magneto will not stay running after it is warmed up. It runs longer in cooler outside temps vs warmer. Once it shuts down it will not start again until it cools down.

- I narrowed it down to spark. When the tractor dies, I pull the plugs and there is no spark
- I replaced the condenser on the magneto, same problem
- I replaced the magneto coil, same problem

Janicholson · Nov 4, 2023

Are the points adjusted to correct gap. there could be a short in the wire going to the kill switch. There could be a distributor cap or rotor fault that happens when temps cause expansion. Jim

cool hand · Nov 4, 2023

Not really familiar with tractor and magneto, but years ago I had those same problems with an IH magneto and had to replace the coil--cured the problem.

grandpa Love · Nov 4, 2023

Sure sounds like a coil issue, especially the part about it cooling off then starting again.

Mike(NEOhio) · Nov 4, 2023

Sounds like the coil as was already mentioned but try just the condenser first. I had a Weed Eater that did that and still did after a $40 coil. A new condenser cured it.

Geo-TH,In · Nov 4, 2023

When my Farmall C loses spark after it warmed up, my mag was full of condensation. I have to blow out the water.
If I ever have to replace the points and cond, I plan to drill a tiny drain hole in the mag..

Fixingfarmer · Nov 4, 2023

Ive had some plugs come in things lately that are gapped .010 lately might want to check that they arent too close if you have not. Manufacturers must only test drive a product for 5 minutes now it warms up gap closes no start. Chainsaw I had came out of the box that way. Not sure what the gap is for a late styled a but I think my unstyled b with the big plugs would be closer to .030

rustred · Nov 4, 2023

you replaced them items ,... but were they new or used??? to eliminate every thing try another mag.

Clundgren · Nov 5, 2023

The replacement coil was new. I did a minor rebuild on the magneto last year replacing the points and condenser and it had good spark after that and ram great, however prior to that I had inconsistent spark not this issue Im posting about. The condenser I replaced with the old one.

I think my next step is checking the gap in my points and plug gaps. Thanks for the feedback!

timcasbolt · Nov 5, 2023

Best of luck on your efforts. Lately, I've had several rude awakenings about the quality of replacement parts for these old engines. No one brand. All of them.

Texasmark · Nov 5, 2023

Not familiar with a Magneto but surely there is a magnetic device (iron core coil of wire) involved and that is what usually quits when heated in a spark ignition system......was when I had spark operated stuff with coil, ignition points, and capacitor spike snubber.

hd6gtom · Nov 5, 2023

Replace coil with new one from NAPA.

rustred · Nov 5, 2023

the points can close if not tightened properly. plug gap is .025, points is less i think .013-.015. just not sure on that mag at the moment.it might be .020 also.

Steven Allen · Nov 6, 2023

Brand new condensers can be bad out of the box.

old · Mar 9, 2024

Clundgren said:
My 1950 JD A with Wico x magneto will not stay running after it is warmed up. It runs longer in cooler outside temps vs warmer. Once it shuts down it will not start again until it cools down.

- I narrowed it down to spark. When the tractor dies, I pull the plugs and there is no spark
- I replaced the condenser on the magneto, same problem
- I replaced the magneto coil, same problem

Very good chance the coil is going bad. As it warms up it is likely to be shorting out internally

JIM MN · Mar 9, 2024

The QUALITY of new replacement parts today is terrible!!!! NO quality control any more on new parts as coils, or condensers .. Do they really test these parts to know they really work before they ship them out?????? The new coil or and condenser are bad!!!

KL in Wi · Mar 10, 2024

Had the same problem years ago on an A. Bad coil

Geo-TH,In · Mar 10, 2024

Clundgren said:
My 1950 JD A with Wico x magneto will not stay running after it is warmed up. It runs longer in cooler outside temps vs warmer. Once it shuts down it will not start again until it cools down.

- I narrowed it down to spark. When the tractor dies, I pull the plugs and there is no spark
- I replaced the condenser on the magneto, same problem
- I replaced the magneto coil, same problem

That happened 2 times on my 1950 farmall C
Moisture, condensation, inside the mag would heat up, turn to steam and short out the spark.
I use compressed air and see water come out of the mag. Then use a hair dryer to get the last of the condensaton out.
About every 2 years this time of the year, the same thing happens to my 2007 GMC work truck.
The distributor cab shorts out and no spark.
Your problem may be something else. Let us know what you find out.
After you dry it out use WD40.

560Dennis · Mar 10, 2024

Coil would very warm , if oil filled would be leaking, something to check

teddy52food · Mar 10, 2024

If you care to send it to me, I have the proper testers to hind out what is wrong. My tester can heat up the coil before testing too. Also have the magnet charger.

JD A no spark after warmed up

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