Farmall M, no spark

bja105 · Jul 5, 2014

My neighbor was baling wth his M and it quit today. It was running very well, then quit, and won't start. I pulled one plug, he is not getting spark.

He has 12.3v to a resistor or something just above the coil, 9.3v to the coil. It is a 12v coil.
What is that ceramic device above the coil and distributor? Does it belong on a 12 volt tractor? Bypassing it did not make it run.

I was planning on getting a coil, distributor cap, and new plugs.
I am just guessing. Rather than throw parts at it, how do I troubleshoot this?

IAtractorKid · Jul 5, 2014

That's a ceramic resistor. Allows you to use a 6V
coil on tractors converted to 12V. Its not needed if
he has a 12V internally regulated coil. If the coil
says its externally regulated, its essentially a 6V
coil and requires that ceramic resistor.

Central Illinois · Jul 5, 2014

You need to find out if you are getting power to
the points. Also you can remove the distributor
cap, rotor, and cover and look at the points while
cranking the engine over. If you see a spark them
more than likely the points are working. If not,
then look closely at the points and make for sure
they are clean where they touch. Sometimes I will
use a screwdriver and with the switch on briefly
touch the points together and seperate them. They
should spark across them. If they check out then
look at the cap and rotor. They need to be clean
underneath and the center of the cap should be
touching the rotor.

El Toro · Jul 6, 2014

Try cleaning the points with a piece of 320 wet or dry until they're shiny. If you need a new coil buy Napa's 12 volt coil IC14. No ballast resistor is required. First install a new condenser and make sure your points are opening and closing. The rubbing block maybe worn. Make sure your rotor is turning when cranking. Your cam gear may have failed. Hal

bja105 · Jul 6, 2014

The rotor turns. Does anyone have a picture of where the points and condenser are?

El Toro · Jul 6, 2014

Remove No1 plug near the radiator and bring that piston to TDC on the compression stroke. Then remove the distributor cap and see where your rotor is pointing. Should be at the No1 plug tower. If its off your cam gear probably failed.
Hal

John T · Jul 6, 2014

Lets take your questions one at a time:

1) "He has 12.3v to a resistor or something just above the coil, 9.3v to the coil. It is a 12v coil."

If its indeed a 12 volt coil??? THERE SHOULD NOT BE ANY EXTERNAL SERIES BALLAST RESISTOR USED or the spark will be weak. A full true 12 volt coil may be labeled "12 Volts" or "12 Volts NOT for use with ballast" or "12 Volts No ballast required"

2) "What is that ceramic device above the coil and distributor?"

Its a series voltage dropping (usually 12 to 6) Ballast Resistor. Its used if the tractor is a 12 volt but the coil is a 6 volt so it drops 6 leaving 6 for the 6 volt coil.

3) "Does it belong on a 12 volt tractor?"

NOOOOOOOOOOOOOOOOOOOOO if a 12 volt coil is
used

YESSSSSSSSSSSSSSSSSSS if a 6 volt coil is
used

4) "Rather than throw parts at it, how do I troubleshoot this?"

See my Troubleshooting Procedure linked below

John T
John Ts Ignition Troubleshooting Procedure

bja105 · Jul 6, 2014

Ok, I found the points and condenser. I don't think the points are opening. When I crank the tractor, I can not see the points move. Should I be able to see them move?

The square shaft on the distributor has slightly rounded corners, not sharp corners. Should it be that way, or is there a point that that shaft should be replaced? Will new points have enough more meat to the surface that touches those corners that it may work?

I also see the coil says no external resistor is required. That means I can bypass that resistor and send 12v directly to the col, right?

Here are some pics. I had a hard time moving the sun or the tractor, so the lighting isn't the best.

bja105 · Jul 6, 2014

bja105 · Jul 6, 2014

bja105 · Jul 6, 2014

bja105 · Jul 6, 2014

(reply to post at 09:33:55 07/06/14)

bja105 · Jul 6, 2014

Here is the setting, on a beautiful day.

TomH in PA · Jul 6, 2014

The rotor and a plastic cover lift right off. Points and condenser are under them. Cleaning the points will often get it running again.

The distributor on an M will look similar to this, but not exactly the same.

John T · Jul 6, 2014

1) "Ok, I found the points and condenser. I don't think the points are opening. When I crank the tractor, I can not see the points move. Should I be able to see them move?"

YES as the engine is cranked the distributor shaft should rotate and the points open each time they come up on the high cam lobes. If they are not opening and closing she cant fire. See if you can adjust them to the proper gap on high cam lobe, that may cure the problem.

2) "The square shaft on the distributor has slightly rounded corners, not sharp corners. Should it be that way, or is there a point that that shaft should be replaced?

Yes rounded and NOT sharp is correct, as the high lobe passes it should open the points to the proper gap.

3) "Will new points have enough more meat to the surface that touches those corners that it may work?"

That rub area can wear down but Id suspect they may just need to be re gapped and that may cure the problem

4) I also see the coil says no external resistor is required. That means I can bypass that resistor and send 12v directly to the col, right?

RIGHT

If you work through my Troubleshooting Procedure it has a systematic method to determine the cause of no spark BUT SHE CANT FIRE UNLESS THE POINTS ARE CLOSING THEN OPENING ON THE HIGH CAM LOBES

TRY TO ADJUST THEM SO THEY DO

John T
John Ts Igniution Troubleshooting

El Toro · Jul 6, 2014

You need new points as the rubbing block is worn off. Hal

bja105 · Jul 6, 2014

Ok , I adjusted the points and have it running. I loosened the screw, and the spring moved it. I tried it a few different places, and it runs best where I left it, but still misses at high rpm. Is this a trial and error thing, or is there a specific dimension I should be setting the points to?

I want to replace the spark plugs, since they are pretty carboned, should I replace the distributor cap, rotor, points, and condenser as a maintenance item, or wait until they quit?

rustred · Jul 6, 2014

you need solid wire core wires for these old tractors. also have them cut to length and installed neatly. those wires are twice as long as necessary. every little thing helps for top performance.

rustred · Jul 6, 2014

the point setting is .020 using a feeler gauge also lube the rubbing block with a very tiny amount of grease with a tooth pick or q tip. make sure the rubbing block is set on the cam's high lobe when adjusting. then turn engine over and recheck your adjustment. using a feeler gauge is just that, you need a feel for it. when you try .021 to check it should not slide between the point contacts.
the next step is timing setting. also even the valves should be adjusted to .017 engine hot.
last is carb adjustment.

John T · Jul 6, 2014

"Ok , I adjusted the points and have it running."

So, adjusting the points so they open and closed as I suggested fixed it yayyyyyyyyyyyyyyy Congratulations

"Is this a trial and error thing, or is there a specific dimension I should be setting the points to?"

YES they set at a specified gap (range of around 0.016 to 0.025 or so depending on cylinders and engine), but I don't have the tune up figures in front of me.

"I want to replace the spark plugs, since they are pretty carboned, should I replace the distributor cap, rotor, points, and condenser as a maintenance item, or wait until they quit?"

If the points are pitted or burned or carboned Id DEFINITELY replace them,,,,,,,,,If the cap and rotor are okay, look good and clean with no cracks or carbon traces I wouldnt necessarily change them.

You're getting there, again congratulations

John T

bja105 · Jul 6, 2014

Thanks for all the help, guys. I think I am going to leave it like this today, so he can bale tomorrow. I only have a few basic tools with me. When I come back Friday, I'll bring feeler gauges, maybe some new parts.

This neighbor does a lot for me. Thanks for helping me help him.

If there is anything else I need to know, tell me.

John M · Jul 6, 2014

Need new points. Those are shot. You set the points by getting the rubbing block on the high part of the square shaft. (turn the engine over to do this.) Move the other piece until you can get a little resistance, setting is .020, on your feeler gauge.

bja105 · Jul 6, 2014

How do I turn the engine while doing this? With three of the four plugs in I couldn't turn it by hand, but I didn't try that hard.I'll be changing plugs anyway, I'll try it with them all out. There is also a place I can get a pipe wrench on the front of the crank shaft.

If I am doing plugs and points, should I do the rotor, cap, and coil, or is that risking getting Chinese junk worse than the old ones?

Can I get new ends to the plug wires so I can shorten the existing, or do I need all new?

Are most of these things available at NAPA?

Thanks everyone. You folks are making me look smart!

bja105 · Jul 7, 2014

The neighbor just called me. The tractor ran fine, they got all the hay that was down baled. Just after they got the wagon in the barn, a downpour started!

Thanks all.

Farmall M, no spark

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