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Hard starting m

U

Underdog

Member
So long story short....
When it was warm here (MN) my m would crank great and fire up as soon as i released the key. (Previous owner wired in a solenoid and key switch from a deere lawn mower). Now that its cold it wont start. Cranks fine but won't fire. Plugged it in for a few hours still no fire. Jumped it with the battery booster and it popped right off. So my thinking is that the coil isnt getting enough juice while its cranking. It has an alternator as well. Question is how do i remedy this?
 
(quoted from post at 13:31:17 12/19/16) So long story short....
When it was warm here (MN) my m would crank great and fire up as soon as i released the key. (Previous owner wired in a solenoid and key switch from a deere lawn mower). Now that its cold it wont start. Cranks fine but won't fire. Plugged it in for a few hours still no fire. Jumped it with the battery booster and it popped right off. So my thinking is that the coil isnt getting enough juice while its cranking. It has an alternator as well. Question is how do i remedy this?
Click to expand...

My SM is the same way. I need fatter cables from the battery. Cold cranking sucks down the juice, so there isn't enough remaining voltage to fire plugs.
I haven't replaced the cables yet as the SM just sits all winter anyways. But come spring time I will be re-doing some of the wiring.
 
All cables and grounds must be 00gauge cable. the smaller automotive cables drop too much voltage on the way.

If you have a ballast resistor in the ignition, bypassing it from the starter side of the JD solenoid with a 12gauge wire going to a 4 amp diode then to the coil side of the ballast resistor. this allows full cranking voltage to get to the coil. The diode must stop voltage from going to the starter from the ignition or it will get hot trying to turn the starter through the ignition.

An alternative: A second "lawn mower" sized battery used for ignition only and separated from the main battery with a 20 amp diode that allows it to be charged, but doesn't allow it to try to crank the engine. Jim
 
Get a common starter switch with 2 small terminals and the battery cable terminals to replace present one if it doesn't have them. Use a 6 volt coil with resister. Use wire from I terminal of switch to coil bypassing the resister. Use present coil wire to resister. Wire from start switch to S terminal to energize starter switch. Seems to help. Other ways to do it but probably the simplest way with what you already have. Common switch is pictured on this starter.
a245777.jpg
 
"fire up as soon as i released the key"
"my thinking is that the coil isn't getting enough juice while its cranking"
I agree and that would be my starting clue for troubleshooting.

Check your coil and resistor if one is used.
If it is a "12 volt, no resistor required coil" and has an added resistor it can give that symptom. If so, remove the resistor. That coil should have about 3 ohms across + to - terminals.

Also a "12 volt..external resistor required" coil should be about 1 1/2 ohms across + and - terminals and have a resistor of near equal value.

Several years ago I bought an 8N Ford and my brother bought a Jubilee. Both had 12 volt conversion kits and both had resistors with too high a resistance (5 to 6 ohms) instead of 1 1/2 ohms to equal coil resistance. If a resistor is used, check to see that it is about equal to resistance of coil + to -.
 
First off is your coil wired properly? If you wire it backwards you will get a weak spark. Make sure if you are running 12V negative ground, that you connect the wire from the ignition switch to the + terminal on the coil.

If you are using a 6V coil with a ballast resistor, and have a solenoid with a terminal labeled "R" on it, you can connect that directly to the + terminal on the coil, bypassing the ballast resistor, to provide 12V to the coil for a few seconds during starting to ensure a good hot spark.
 
Try this and if it fires right up then I can tell you how to add a wire to make it do that every time.
Hot wire it as in wire from the ignition side of the battery to the ignition side of the coil. That will bypass the ballast resister it has or is likely to have. If that does not help then it is likely to be a starter going bad and pulling to many amps
 
I cant think off hand if there is a resistor in line or not. I will check it out when i get home and report back. Ive owned this tractor less than a year and have been slowly but surely been fixing the hack jobs of the previous owners
 
Most 12 volt conversation have a ballast resister due to the fact the person did not want to bu ya new coil since the old coil is still good. But then you know how most farmers are they want to save $$ when ever they can
 

Actually, if that M or Super M has been converted to a 12 volt system, you do not need the 00 cables. #2 or even #4 would be sufficient. Look under the hood of your truck with a 350 cubic inch engine. What size are the battery cables? If those cables are good enough to crank 350 cubic inches, why would they not crank a 248 cubic inch engine?

One of the big differences between 6 volts and 12 volts.
 
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