ign. coil

I am working on a M farmall - it has 12 volt -- it doesnt like to start till ya let off the starter -- it has a voltage reducer before the coil and the coil is suppose to have one-- if I change to a 12 volt coil( no reducer needed) will that cure the starting problem? Roy

Sounds like a bad connection to the coil or switch and wires going to the stater where the solenoid is that has IGN connections. IT should have a wire direct for starting and a wire through your ballast resistor for the voltage drop down you mention. Try a wire direct to the coil from the battery next time if it starts like it should you found your problem. Don't leave it on after it starts though.

Probably not but if the resistor (voltage reducer) is bypassed during the start process, that may help. But It sounds more like your starter may be dropping the voltage lower than it should or the battery is not capable of delivering what the starter needs or battery cables/clamps may be corroded. A volt meter would help find the problem.

(quoted from post at 17:10:51 06/15/22) I am working on a M farmall - it has 12 volt -- it doesnt like to start till ya let off the starter -- it has a voltage reducer before the coil and the coil is suppose to have one-- if I change to a 12 volt coil( no reducer needed) will that cure the starting problem? Roy

Click to expand...

The advantage to using a coil needing an external resistor is that it can be bypassed during cranking, when the starter is drawing down the battery voltage to make for a ''hotter'' spark.

Is yours set up that way?

https://farmallcub.com/rudi_cub/www...s/GSS-1310 Electrical/GSS-1310 Electrical.htm

Primary resistance and bypass info on Pages 34 and 35.

If its a 12 volt tractor that uses a 6 volt coil ??,, plus a series voltage dropping (12 down to 6) ballast resistor ??,, PLUS the ballast by pass feature while cranking ??,,that can improve cold weather starting I WOULD LEAVE IT (repair as needed) AND NOT USE A 12 VOLT COIL......If it had a 12 volt coil PLUS the series ballast still in place, coil voltage would be low and the spark weak

The ballast by pass function circuit may not be all in place and wired and working correctly thats causing your problem.

If thats what you have ?? and its all in place wired and working correct ?? ONLY WHEN THE STARTER IS ENGAGED there should be unballasted battery voltage on the coil (ballast is by passed jumped around with battery voltage direct to coil) and then when in the normal RUN power goes to and through the ballast and then to the coil so you have 6 left for the 6 volt coil.

What may be happening if the by pass circuit isnt working is when cranking battery voltage is reduced causing a weak spark but when no longer cranking voltage rises making a stronger spark so she starts

Low voltage when cranking may be caused by too small cables,,,,,,,,weak battery,,,,,,defective starter drawing excess current,,,,,,,,,bad cable or bad ground or battery connections CHECK ALL THAT ESPECIALLY BATTERY CABLES AND GROUNDS

Also check if it has a ballast and its good and continuous with correct resistance (around 1 to 2 ohms or so) and insure its wired right and that when cranking the ballast gets by passed so battery voltage gets to the coil ???????? Check the wiring from an IGN terminal to the coil (NOT from ign switch TO ballast) to insure WHEN CRANKING battery voltage is indeed getting direct to the coil (NOT having to pass through ballast) Check wiring from switch/solenoid up to coil (same location electrically as output side of ballast) thats the ballast by pass while cranking feature

John T

Here is how to do a Resistor bypass: If your tractor has a relay/solenoid with 4 terminals one small one should be marked with an I. If so all that is needed is a 12gauge wire from that terminal to the coil side of the ballast resistor. if no I terminal, Run a wire from the starter motor side of the starter switch (if it has a relay/solenoid) still the same big terminal to the starter motor) then put a 6 amp or heavier diode in series with the wire so the current only flows away the starter, and toward the resistor. The diode prevents the ignition from trying to run the starter motor. Jim

That is a classic symptom on a tractor with resistor starting bypass. The M did not originally come with that feature, so unless it has been added some how that is likely not the problem. If a bypass system was added there should be an extra wire going to input of coil.

A couple of things I would check:

1. Is battery fully charged

2. Check the wire connections on 2 small posts on coil. Negative ground negative post to side of distributor, positive ground positive to side of distributor

3. Check the resistor (voltage reducer) in line to the coil. It should be about 1 1/2 ohms. I've seen several conversion kits with higher value resistor and it will cause your symptoms. If the resistor had too much resistance changing to a 3 ohm primary direct 12 volt no external resistor coil required could cure the problem.

4. Be sure battery cables and connections are clean and in good condition, especially where ground cable connects to frame. I like to attach them to the frame as close to the starter as I can.

5. You can bypass the resistor and see if that makes a difference in starting. Don't run it very long with bypass in place but that should confirm if the resistor is your problem.

My jubilee was doing the same thing and there was no way to bypass the ballast. So I connected the cathode end of a diode, the white

stripe, to the coil. The other end of the diode is connected to the starter's power wire.. it works fine now..

Your battery's cranking voltage is less than it should be.
Might check out the condition of the battery.

For Geo & NIcholson, tell him how to attach a wire from his starter motor terminal to the diode.....I want to know too.

To the little terminal that is only energized dying cranking .

Farmall Ms I have seen have a separate standalone starter switch, not a saddle mount. Jim

(quoted from post at 11:23:53 06/16/22) Farmall Ms I have seen have a separate standalone starter switch, not a saddle mount. Jim

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Doesn't matter. The function of the switch is the same.

Connecting a wire from that switch to the coil won't work because it will be trying to energize the starter.

This post was edited by BarnyardEngineering on 06/16/2022 at 11:42 am.

Jessie,
That starter will require a little redneck engineering to bypass the ballast
resistor;
You will need to attach a NO switch to the control rod so when you pull on the rod,
the switch closes and applies the full 12v to the coil. No diode needed.

Or you could remove the cover on the end of the starter. Attach the wire where the
power comes. Then run it to a diode..

Going to need to get creative using that old starter.. May require taking the starter
apart to get ahold of the power in wire..

Cant. It would be hot all the time.

No, if a wire is connected to the switch in the pic JMOR supplied, there will be power to the coil ALL the time,
unless its switched between the coil and starter switch. The battery cable attaches to the switch on that starter,
and any other wires would have to attach to the same post.

(quoted from post at 12:09:40 06/16/22) No, if a wire is connected to the switch in the pic JMOR supplied, there will be power to the coil ALL the time,
unless its switched between the coil and starter switch. The battery cable attaches to the switch on that starter,
and any other wires would have to attach to the same post.

Click to expand...

An M starter switch is not mounted to the starter like that.

It has two terminals, one hot all the time, and one only energized when the button is pushed.

This second terminal can't be used to boost the coil during starting because the power would be "backfed" from the coil into the starter. It would burn up the coil wire from trying to power the starter.

Im well aware of how an M is set up. Ive owned more than my fair share of them. My responce was what you said about
the switch on the pic JMOR provided, which only has one hookup. I thought you were implying it had more than one in
my first responce.

(quoted from post at 15:31:43 06/16/22) Im well aware of how an M is set up. Ive owned more than my fair share of them. My responce was what you said about
the switch on the pic JMOR provided, which only has one hookup. I thought you were implying it had more than one in
my first responce.

Click to expand...

idn't mean to start a war.....just sayin that with the start switch on my Farmall (as pictured) , it would be next to impossible to connect a wire to the starter motor terminal. That's all. Original poster's may differ???