Ignition coils failure,Super M ( Junk coils???)

mike1972chev

Well-known Member
Hey, (It has been awhile!) I am a little ashamed to have to ask questions on this one,but here goes. I have recently replaced my original 6 Volt IH coil with a replacement 12 Volt (2.8 Ohm) from Steiners part # IH 237 The ORIGINAL reason for doing so was the coil would quit firing after getting warm from use.(ORIGINAL coil was ballasted correctly for 12 volt conversion to a total of 3 OHMS.)

Well... flash foreward to the NEW IH 237 Steiners coil being installed.It TOO is quitting after about a 20 minute period of use????? (THIS coil was ALSO properly ballasted with a .5 ohm resistor to get it in the 3 ohm range)

So now I am thinking I got a bad one???? AFTER the coil cools off for about 20-30 minutes ,it now runs like a CHAMPION again,but then quits after about the 20 minute run time as has been the case. :( I IMMEDIATELY,on the spot quickly swap coils after it quits to another stock 12 volt coil and it runs amazingly!!!!(THIS coil being a larger bodied 12 volt coil like a 12 V Delco that Ohms about 1.7 so I ballasted accordingly)

Well,I mount the latest,larger bodied automotive coil and run IT for awhile......... IT quits firing strong after about the same time as the others and we have no ignition once more.
I have since did some updates I wanted to do anyway, Pertronix ignition conversion,(Points looked BAD and slightly burnt)and a brand new set of NGK plugs..... STILL quitting after about the same 20+ minute run time and NONE to WEAK fire out of the coil.

After everything cools off...... RUNNING again?????

Only thing I have NOT done is plug wires,but the ones are on it are recent(like a little over a year ago and NOT much use.) I want to check resistance in them,but want a new set to have anyway. I am also considering a 3 ohm Pertronix coil as well,but am NOT convinced this will cure anything at all????

I can find no grounding issues in the VERY simple wiring of this tractor either.


I am loosing my mind a bit on this one.. Any ideas????
 
Did your Petronix kit specify a resistor?

There's another post below about an M with running problems, and one of the posters said that if you specified 12V when you ordered your Petronix kit, you don't need a resistor.
 
It IS the 12 volt kit,but the resistor is for the COIL,not the Electronic ignition module (Being it is a 4 cylinder engine, Pertronix technician is telling me 3 Ohms of resistance because of DWELL in the distributor.)
 

100% correct Mike. I think some folks are getting that mixed up. I've gotta get a smaller multi meter so I can check everything out, make sure I've got right ohms resistance. If I have to much, I could be getting weak spark I imagine.

Same for you. If you don't have enough resistance, you will fry a coil. It doesn't happen immediately. Say you go out and hog for 1-4 hrs, then you'll get a failure cuz it will over heat. I think 4 amps is the goal, don't quote that. Google it up you'll find the info.

GL

Chance
 
Chance: again,Pertronix tech was telling me NOT to go OVER the 4 ohm but 3 OHM was ideal!

He is telling me that when you get to 4 OHM and more that it could cause a firing issue at higher RPMS,but these IH 4 cylinders DO NOT turn any
kind of serious RPMS in my book. (distributor should be turning at about 750 rpms MAX on my tractor......)

I COULD try adding some MORE resistance to the coil and see if that helps???????
 

Yup, 3 ohms is goal to achieve 4 amps to coil. If you have that then you are good. Maybe a funk coil? How many have you fried?
 
Well,ALL coils will currently still fire and work UNTIL you get some run time on tractor.....THEN tractor backfiring ,stumbles,them quits. Will
not restart. Pull coil lead and crank engine WEAK,to NO spark.

Let everything cool down,then it runs beautifully again until warm.(I HAVE dumped my ice water I carry with me on the coil,and we are running
shortly after.) Coul wire is arcing a strong,blue spark.
 
You seem to have a collection of resistors to select from. Instead of attempting to select the "correct" or "specified" total resistance I would suggest adding an extra ohm and see if that clears the problem.

I have measured the primary coil resistance before and have found it difficult...in that different meters give different readings. I have a Fluke 88 and zero out the leads however, I still question how accurate the reading is. Perhaps your actual resistance is not what it seems per the measurements.
 
A bad wire will sometimes work when cool but as things warm up resistance increases. About 50 years ago Dad had a
Chevy pickup that would run fine cold and miss when warm. Turned out to be bad wire.
 
IT is doing the same issue on a BRAND new set of NGKs (AB-6)I put in it this weekend as it was doing with the 2 year old set of AC Delcos( C
87)

They look a little "rich" when removed,but as expected with incomplete combustion ... due to WEAK/ NONE ignition!

I am tempted to go to the U.S. Nationals this coming weekend and steal one of Tony Shumacher's MSD Mags of his Top fuel car and put on the
"D@MNED thing at this point!!!

I have to be overlooking something????
 
Yes,THE ONE of things I have not changed yet. Would ALSO cause resistance in coil and would OVER HEAT it as well.

I need to check resistance in the plug wires. (NOT that old of wires.) I will be getting another set anyway just to have.

Was thinking this also as I was driving this morning......
 
Mike..Why not just use the flame thrower 3 ohm 12 volt coil instead of trying to cobble parts together. I have one on my SM and H and have not had a lick of trouble. They are not expensive, put out good voltage, and fit.

Pete in NC
 
Not the plug wires, any of the connections in the primary system that feeds the coil could be getting hot and causing the problem. Your problem seems to be too consistent across coils for it to be the coil. They aren't all bad and failing when hot is pretty rare. Do you have anything else that uses a coil that you could switch a coil into to prove it will fire for more than twenty minutes?
 
If several coils and resistors appear to fail in exactly the same way I would shift my thinking.

Compare the voltage at the coil input before you first start it and when it fails? If voltage drops off start checking back through switch to battery.

Bad switch or wiring could cause those problems.
 
I have ACTUALLY had a total of 4 tried on it. Two were brand new,I proven ,used one,an original that is 40-50 years old now.


At this point,I am thinking bad plug wires with A LOT of resistance in them,or a bad ground/bad primary wiring,or connection SOME WHERE???? Everything else is new now.

This system is SOOOOO simple there is just NOT much area for it to fail........

I am checking battery cables and all chassis grounding tonight. might bypass ignition switch and ammeter and run it for awhile hard tonight.
 
Are you using the same ballast resister? If so after it gets hot it maybe opening up try with wire only and see what happens
 
Disconnect + side of coil and run a jumper wire, alligator clip on each end, directly from the battery to the coil and see if the problem goes away.

Somebody here a while back had a similar problem and it ended up being the ignition switch!
 
The original Kettering system would charge the coil continuously which is why a 10-20 watt ceramic resistor was needed especially when the engine was just sitting with the ignition on and the coil would get hot. I don't know about the Pertronix system, but a good electronic ignition will just send a pulse through the coil and not load the coil.

I used to put Delta, Tiger, or Heath Kit iCD gnitions on vehicles and all they used the points for was to sense the point closure or opening and precise dwell did not matter. The points also did not have to be polished clean because they did not carry much current like they did with the Kettering system.
One other thing that will cause a sytem malfunction is a bad internal ground in the distributor housing. I have seen this on a Ford Jubilee. When I bypassed the normal system and shunted in a Toyota point triggered system (from one of the 70s hybrid pickup ignitors) the tractor ran fine. When I removed it no amount of twiddling with the points or carb would make it run right. It just skipped and ran rough because the charge lRC time constant was messed up by excess R.

I just went to the Pertronix site and after reading it I am not sure which Pertronix system you have. If you are just replacing the points with a breakerless system it could still have a problem with a bad ground. Also since things seem to go bad after the tractor runs awhile it could be a bad Pertronix unit.

You need a precise ohm meter to read the resistance on the distributor, and the external lead going to the distributor. Another way to test is to add a resistor to the external lead and measure the voltage drop across the resistor if your ohm meter does not read accurately.
 
NO, Ballast is being changed to match type of coil used .

With the new IH 12 V replacement,it is at 2.8 Ohms and I was told MIGHT not even need to be ballasted,but I had added.5 of resistance to get it into the 3 ohm range.

I am checking ALL connections tonight. If the ignition switch IS getting hot and quitting, I am gonna be "PO"d for sure.... lol
 
Might want to measure amperes flowing through coil when not running. Four amps max is pretty much standard.
 
On my 450 it wouldn't start, had no spark no matter what I did. On a lark, I decided to run a separate ground wire from the distributor body to the tractor chassis. Problem went away, hasn't come back in two years. Just sayin'.
 
Hugh McKinney,
Thanks for posting that.
The is exactly my point. The ground may be intermittent, loose, or corroded and cannot be seen. It does not take much resistance from this to cause problems. Less than one ohm.
 
I read that you changed the points to a pertronix ign system and what I'm going to say may sound a little off but change it back to new points and condenser and see what happens ain't no way you got 4 bad coils,i worked on a stump grinder with a 4 cylinder Wisconsin and it was about to drive the man crazy after he replaced the ign system except for the condenser because it had a long led and he couldn't find one,it ran about 15 minutes after I got there and shut down sounded like it ran out of gas checked the fuel system couldn't find anything, fired it back up ran another 15 minutes same problem again,i installed a new condenser and spliced the wire to make it fit,that was his problem the whole time,a bad condenser cost him 2 days work plus parts and labor
 
As you run it tonight, Put a volt meter on the battery and watch the charging voltage. Some nasty to diagnose regulators get into thermal runaway and vharge more than 18 volts after getting the starting charge back into the battery. Jim
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top