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DOC: I think I would start with when did the problem first
start. You said that most of the ignition system has been replaced. Were you driven to replace parts because of the problem, Or because it was time for a tune up? For example if the plug wires are RF "radio Frequency" supression type with to high of a resistance value It could make your coil work to hard. Most coil & plug wires have a resistance value per foot. Example 50 ohms per foot may be typical for a car. could you retry the old wires? Next I would carefully check the primary and secondary start/ run circuits. Some ignition systems are designed to have a 2 step voltage or current limiting device to feed the coil.
start would let full battery into the coil to allow full saturation of coil this in turn would let the highest secondary step up voltage out to the plug wires to assure the engine will start. When you let go of the key some ignition systems will have a fall back device as mentioned
before. this could be resitor in the loop to drop the voltage to the coil once the engine starts and you let go of the key. A classic example would be the dual ballast resistor used on the Dodge,plymouth,Chrysler for over 40
years. Without knowing the exact schematic layout of your machine I can only guess that it is a series loop. Battery, ignition switch,possible resistor as mentioned,coil,return to chassis ground, back to battery. If anything in this loop
has high resistance or short to ground it could cause the coil to over heat. Things that I would try is to run a hot wire from the battery to the plus side of the coil and jump the starter solenoid out momentarialy to start the tractor.
please be advised DO NOT DO THIS IF A RESISTOR IS IN THE FACTORY LOOP, OR IF IT IS A ELECTRONIC IGNITION. this would just burn up the new coil. You mentioned points so this rules out the electronic ignition.if you do try the jumper wire to the coil with the other wire off and tied back, and the tactor stays running you almost have your answer. This would mean a faulty ignition switch or faulty wireing. Did you check the dwell when you set the points? If you have to much dwell I think this could cause the coil to work to hard as well. Did the new coil get damaged internally from the existing problem? Some times coils will drip out the oil used for internal cooling and still work untill they heat up. After this long list I'll give a shorter one.
1 coil wires correct resistance
2 Ignition switch ok?
3 wireing ok?
4 dwell set ok?
5 resister if used ok?
6 engine ground ok?
7 correct plugs with correct gap?
8 condenser if used ok?( typically only for)
cars with radios
9 modifications to oem system ie:
add on accesories possibly tied into ignition
primary for power?
10 diodes if used in system ok?
11 teminals, binding posts,bulkhead connectors,
all tight?
12 last and least likely, electricity can do
weird things alternator voltage regulator

I hope this helps you out keep us posted on out come if you need more help let us know.

MF135 Overheating coil
Massey Ferguson Tractors
Replies 12 Post by ROBDEERE

TIME FOR A MAJOR APOLOGY TO POSTING/SCREENNAME
"(THESTRAIGHTDOPE)" I put my big size 11.5 foot in my mouth,and was so quick to react to the comment on another individual indicating it was ok to try and hide the $1200 rebate from the customer that I actually put in the wrong name on who to reply to. At this time I would like to name who it was intended for , but I think I have already said one to many names, Besides 99% of the people on this board are sharp enough to figure out who it was really intended for. ONCE AGAIN MY APOLOGY

JD Ten Series Rebate Question
John Deere Tractors
Replies 57 Post by Robdeere