No spark when cranking 128
 

I was going over the old 128 getting her ready to cut grass and she wouldn't start. I checked for spark and zero. I dove in and found the point block where the wire from the coil connects burnt up pretty bad. I had put new points in last spring when I used the tractor for the first time after inheriting it from my late uncle and ran it without issues. I believe the coil is not original and due to the damage to points, is not internally resisted (not marked either way) . In an effort to make a quick fix, i flipped the points insulator block over (less damage) and reinstalled the wire from the coil. It is not making a contact to ground now as best i can tell visually. I set the points at .020 gap. I also installed an external resistor that i had in the wire from the ignition switch (which goes to the positive terminal on the coil. I am now getting 13 volts at the coil and points. Still no spark at the plug when cranking so i checked the coil with an ohmeter and it was open. I checked another used coil i had as well as the coil off my running super c. Both had 5 ohms. I installed the used coil and the coil off the super c and neither will give spark at the plug. I ohmed the old plug wire and it reads 4 ohms. I tried a new plug wire from a set i bought for my pickup project as well. Still nothing. I ohmed this new wire and it read 1000 ohms. (???) i tried the old and new plug when checking for spark. I cant figure why the points dont spark when i open and close them manually. Still shorted out from the melted block i suppose. guess i will start throwing parts at it next week; new internally resisted coil, new points and new plug wire. Any suggestions?

Refer to the following link for checking the coil....

https://www.onlycubcadets.net/forum/showthread.php?t=11

The coil should be to spec on continuity and also be the correct replacement part. Isn't the super C tractor a 6 volt system?

Also, check for continuity from negative wire removed from coil to ground with the points open. There shouldn't be any. With points closed, should read low resistance.

I don't think there is resistor in the plug wire, but others will chime in. Usually no/low resistance on the plug wire.

Finally, replace the points anyway.... If it is burnt, it is likely done. Do replace the condenser while you are at it.

Thanks Billy-O for the guidance. I have swapped a few points and troubleshot ignition gremlins a few times over the years. This is the first time I came up scratching my head. BTW, the Super C was originally 6 volts but has been converted to 12v. I forgot to include that.

Is there power to the coil when the key is in the "crank" position?

You may have answered this but I'm not sure: If you manually open and close the points when the key is in the ON position do you get spark?

Is the condenser shorted/leaky (resistive)?



Just some ideas.

There was power to the points when cranking.

I was not getting spark at the points with key on and manually opening and closing them.

Condensor is good.

I happened to remember that there was still a coil on an old parts tractor I had. (CC 73) so I took it off and checked it. (It ohmed out at 35 ohms) i figured i might as well try it. Guess what? SPARK!!! I also robbed the insulator off the ild points in the 73 while i was at it and swapped it out later. I have a new coil on the way, since I was out of “spares”! I have no idea why it will not work with the coil off the Super C, though, as I reinstalled it and it started right up!

Power at the points but no spark.....
Dirty or damaged points. Drag a piece of 220 grit though them a few times, and recheck after resetting the gap. For best results, static time the engine.

One more check
 

Just a thought... Be sure the condensor is getting a good ground by being sure the connection is shiny and tight, (maybe even using a jump wire to insure a proper ground.) Happened to me once. Good luck. Carpetbagger