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farmall m hard start

N

Noah Washine

Member
ok im back on here again with my m... so now all of a sudden it dont want to start real well. it just cranks and cranks and cranks...we pulled started it multiple times and every time it starts and runs great. so could it be electrical? it has a mag and someone told me it could be a spring inside it thats worn out. could it also be the coil? im lost on what it could be, i replaced all the plugs and wires. and also replaced the cap rotor and condenser. so it could only be the coil or that spring i would think. but im not sure. thanks for all your help.
 
(quoted from post at 22:05:00 06/22/22) ok im back on here again with my m... so now all of a sudden it dont want to start real well. it just cranks and cranks and cranks...we pulled started it multiple times and every time it starts and runs great. so could it be electrical? it has a mag and someone told me it could be a spring inside it thats worn out. could it also be the coil? im lost on what it could be, i replaced all the plugs and wires. and also replaced the cap rotor and condenser. so it could only be the coil or that spring i would think. but im not sure. thanks for all your help.
Click to expand...
've seen situations where a weak battery didn't have enough oomph to spin the starter and still provide good primary voltage to the coil. Might be worth a look.
 
If it has a magneto it would run without a battery so that's not the
problem. The magneto should produce a distinct and fairly loud clicking
noise when running the starter or cranking by hand. That noise is the
impulse mechanism tripping and causing the magneto to spin fast as the
rotor goes past each tower in the distributer cap. The magneto produces
its own spark so this extra speed is needed to produce a hot spark at
cranking speed. You need to check for spark at each spark plug. You can
just hold a plug against a good ground or as I do use a rather
inexpensive spark tester. Spark tester is a threaded shaft with a point
on one end that can be adjusted to give you the spark gap you want. An
alligator clip on one end allows you to ground it and a tip on the other
end looks like the end of a spark plug where the wire goes on. It makes
checking spark easy especially if you don't have a helper.
Dave
 
It appears Mr. Tim did not read your statement about
the magneto, crank voltage has minimal affect on a
mag that is working correctly. I am not much of a mag
guy but I do know if you get tangled up in one the
definitely get your attention. I assume you have check
the fire since you did the repairs to it. You end up
putting a new coil on? No matter how slow you turn it
once the impulse lets go it should click over and fire a
spark. Usually a nice blue one that can jump 3/8 inch
or more. Fo you do hear the impulse when you crank
it?
I am attaching you previous post on this.
Previous post
 
I would say it's probably the impulse spring if it runs good after pull starting.

Could be low compression. If it idles well good chance the compression is okay.

If it runs good under load the ignition is working.

Do you hear the impulse spring clacking in the mag when cranking? If not, it's not working.
 
Mags make their own electricity by spinning a permanent magnet inside a coil. This electricity is then shut off by a set of points .013 inches
opening when the little cam in the mag is pushing the points wide. Shutting off this internal juice causes a high voltage spark. When cranking
with a hand crank, or electric starter, the mag doesn't spin fast enough to make enough voltage to fire the plugs. SO the drive that hooks the
mag to the engine has a coil spring in it that is used to spin the mag fast when starting. the catch and release of the spring makes a pretty
dramatic clicking noise. Pulling the tractor causes the engine to be turning fast enough to not need the spring device. The drive device is
called an impulse coupling. If you tractor doesn't click when cranking, I suspect the mag drive needs to be rebuilt. Jim
 
your impulse coupling is not working. turn it with the hand crank and listen for it to click , that is when it produces the spark to fire the
plugs. one thing about magnetos. the tractor will start with only a slow turn of the engine. plus them springs and pawls get sticky and many
times need to be cleaned. nothing hard to do. the pawl has to be free to catch when being rotated and if sticky this will never happen. need
to remove mag and give it a cleaning. the way it is now it is not producing the spark needed to start. get someone to turn the crank and hold
the plug wire you will feel only a very faint spark amounting to nothing.
Untitled URL Link
 
the time the points are closed is the dwell and in this time the condenser is storing the voltage so when the points open you have a big blue spark jump the plugs. and the impulse causes a fast rotation of this procedure.
 
Rust red I humbly disagree. When the points are closed (Kettering ign. or Mag.) the condenser is shorted to ground. it does two things, lowers the arcing of the points when opening, and rings with the primary discharge giving spark duration. Jim
 
far as i know when the points are closed the condenser is getting charged up. that is what is producing the blue spark through the coil. and yes prevents arcing at the points. and your saying it dont get charged?
 
(quoted from post at 22:52:35 06/22/22) It appears Mr. Tim did not read your statement about
the magneto, crank voltage has minimal affect on a
mag that is working correctly. I am not much of a mag
guy but I do know if you get tangled up in one the
definitely get your attention. I assume you have check
the fire since you did the repairs to it. You end up
putting a new coil on? No matter how slow you turn it
once the impulse lets go it should click over and fire a
spark. Usually a nice blue one that can jump 3/8 inch
or more. Fo you do hear the impulse when you crank
it?
I am attaching you previous post on this.
Previous post
Click to expand...
y apologies. Lost my mind there for a minute.
 
I agree with everyone about the weak impulse spring. I once had an M and it got to be hard starting, but you could pull it
10 feet and it would fire right up and run like a champ. Took the mag to a shop, the guy put it on his machine and every
time it fired it would throw a spark that would jump an inch. Finally disgusted with it and put a distributor on it and it
worked great. My conclusion was that pull starting, or with the mag on the tester, it was turning fast enough to produce a
good spark at the higher speed hand cranking, or turning it over with the starter wouldn't get a spark. Just my experience.
 
Jim is right. When the points open , the field collapses which produces a wattage in the coil primary which tries to arc at the points. The condenser absorbs that charge to keep the points from burning. The voltage coming out of the coil is many times what is going in to it. This voltage in the primary acually bounces back and forth between the condenser and coil. What we see is a spark, but it is many , many sparks so close together that it looks like only one. They say it makes the coil ring. The spark is coming from the secondary windings which are picking it up from the moving field. Clear as mud?
 
well i guess no one went into detail to explain all that. or i just dont remember from class 45 years ago. so i am not wrong anyhow by saying it gets charged up when the points are closed and prevents point arcing. clear as samahunka .
 
(quoted from post at 21:15:42 06/22/22) well i guess no one went into detail to explain all that. or i just dont remember from class 45 years ago. so i am not wrong anyhow by saying it gets charged up when the points are closed and prevents point arcing. clear as samahunka .
Click to expand...

''so i am not wrong anyhow by saying it gets charged up when the points are closed''

You are WRONG, (as I have been many times).

The breaker points shunt across the condenser to ground when they are closed, NO charging of the condenser goes on during that period.

Time to suck it up and move on, IMHO.
 
I have an Oliver 70 that was the same way. It has a mag. It would turn over good with the starter but, would not start. once in a while it would fire on one cyl but not start. If I pulled it with another tractor, it would start in a couple feet. Impulse was working fine. Tested for spark, nothing at starter speed. Sent the mag out to a repair shop. He as a variable speed test stand. At starter speed it would spark once in a while. Get it above starter speed and it worked perfect. Again, the impulse worked fine. Ended up being a bad coil. Replaced the coil and it's been starting and running perfect since.
 
Have you tried to use a second battery to get the starter to spin a little faster? I understand that a mag doesn't need a battery to start the engine but the speed of the starter rpm may need to spin a little faster for the mag to work properly.

This won't fix the underlying problem though.
 
(quoted from post at 23:22:09 06/22/22)
(quoted from post at 22:52:35 06/22/22) It appears Mr. Tim did not read your statement about
the magneto, crank voltage has minimal affect on a
mag that is working correctly. I am not much of a mag
guy but I do know if you get tangled up in one the
definitely get your attention. I assume you have check
the fire since you did the repairs to it. You end up
putting a new coil on? No matter how slow you turn it
once the impulse lets go it should click over and fire a
spark. Usually a nice blue one that can jump 3/8 inch
or more. Fo you do hear the impulse when you crank
it?
I am attaching you previous post on this.
Previous post
Click to expand...
y apologies. Lost my mind there for a minute.
Click to expand...

A good man will acknowledge his mistakes. Well done.



This post was edited by Carlmac 369 on 06/23/2022 at 05:22 am.
 
I had a mag with a weak magnet that wouldn't start or was very difficult to get started. Shop tested it and put in a new magnet and now it starts instantly.
 
the condenser is grounded on its can cover. the wire is attached in all cases to the movable side of the points. The screwed down side of the points are grounded. When the points are closed there is a circuit path through the condenser wire through the points to ground from ground to the condenser can. this would allow no charging at all, and a clear shorting of the voltage in the condenser. No charging up when points are closed. Jim
 
Had a 1952 or was it a 1953 H like that. By serial
number 300 from last H built. After a lot of WTFs I
had an Electric shop in Racine Mn go through starter.
Now it starts on first or second revolution. Starter was
sucking too much juice leaving a poor spark.
 
well ok , i just looked it up for myself... the condenser is absorbing current when the points are OPEN not CLOSED as i said. so why could
you not say that. instead i get a suck it up comment.
 
(quoted from post at 09:20:08 06/23/22) Have you tried to use a second battery to get the starter to spin a little faster? I understand that a mag doesn't need a battery to start the engine but the speed of the starter rpm may need to spin a little faster for the mag to work properly.

This won't fix the underlying problem though.
Click to expand...

no but the battery i have on it really spinned that engine over fast.
 
(quoted from post at 08:19:01 06/23/22) I have an Oliver 70 that was the same way. It has a mag. It would turn over good with the starter but, would not start. once in a while it would fire on one cyl but not start. If I pulled it with another tractor, it would start in a couple feet. Impulse was working fine. Tested for spark, nothing at starter speed. Sent the mag out to a repair shop. He as a variable speed test stand. At starter speed it would spark once in a while. Get it above starter speed and it worked perfect. Again, the impulse worked fine. Ended up being a bad coil. Replaced the coil and it's been starting and running perfect since.
Click to expand...

interesting thats exactly how my m is acting. im prolly gonna replace the coil. i think it might even be original or at least very old. i wondered if the coil was bad cause when i turn it over i hear the impulse working.
 
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