1942 Case VC12 tractor- PointsCondenser

[Mallary]

I am trying to figure out how my battery & coil work together to produce the charge that then powers the distributor, that powers the points to create a spark?? I ask because my tractor is losing power and unable to produce a spark. Anything to help me figure this out would be appreciated. Thanks

 

[Jack Murray]

You can find descriptions for cars online, it is the same, but I'll explain the theory if it helps.

The coil is a transformer with two windings, primary and secondary, the primary charges up when 12v is on and the points are closed, then the points open breaking the ground path of the primary, and so the charge in the coil now tries to find another path to ground, and the secondary has 40,000 volts, which is such high voltage that it can jump across the .035 gap, and finds a ground path through the spark plug,
and creates the spark.

The secondary output goes out the coil wire, into the distributor to go to the specific plug in the firing order. The wires can be worn out so the ground path doesn't make it all the way to the spark plug, but arcs from the wire to somewhere else. Or the distributor cap connection to the rotor is worn and same result.

If the points are worn, or misadjusted so it doesn't open and close properly, or the distributor cam which opens and closes it is worn, or the bushing in the distributor makes it not spin in a circle, but in an oval or just sloppy, it won't open and close the points properly, so the coil isn't firing or charging with the right timing or at all.

You can rotate the engine manually and check the point gap when open, can't remember the setting, .020 I think.
Check the distributor shaft wear it shouldn't move much at all back and forth.

Put a timing light on each plug wire, and see if it is firing consistently.

hope that helps.

 

[DCTOM]

id it runs good when cool than loses power when warmed up check coil could be bad

 

[Bob]

Cut and paste this link into your browser.

http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/FOS-20%20Chapter%206-Ignition%20Circuits/index.html

It is a scan of the DEERE FOS for ignition, hosted on the Farmall Cubs site. (Of ALL places!)