Farmall Cub

I am having a problem starting. Cold starting is difficult, hot starting is almost impossible. No spark at the plugs (no 1 had a spark when it turned initially (ie about less than a second) and then nothing. I also checked at the coil wire (where it does into the distributor cap) and there was no spark there either.

So now I am going to change out coil, points, condenser, and while I am at it, new distributor cap and spark plug wires!

My question is ... is it easier to do all of this by taking the complete magneto assembly off the tractor? Or is it just as easy to do it in place?

David,

It can be done in place, but it's always easier to do a good job at the bench. To make it easier...crank the engine till the rotor points to #1 and don't move the engine till the mag is back in place.

If it were mine, I would clean the points and replace the condenser and try it before investing in a coil. Just so you know, the mag doesn't have a safety gap... so the coil can be damaged by turning the rotor without a load on the output.

When you go to get wires - get "Tractor wires" a metal core wire not Carbon core wires.

Metal Core wires run about $9.00 a set and are well worth the trouble to make-up the distributor ends.

George:

Is your suggestion due to the $40+ cost of the coil? The reaosn why I ask, isn't the coil responsible for producing the spark? Doesn't the condenser just smooth it out? Now what do the points do again?

David

David wrote:George:

Is your suggestion due to the $40+ cost of the coil? The reaosn why I ask, isn't the coil responsible for producing the spark? Doesn't the condenser just smooth it out? Now what do the points do again?

David

David,

A lot of us would like to know where a coil for a mag can be bought for $40! I wouldn't spend it unless the old coil is KNOWN to be bad. Yes, the magnetic flux collapsing in the coil produces the high voltage for the spark, but the points must make and break crisply for that to happen. One of the duties of the condenser is to help them do that. They MUST be clean and bright to work.

I prefer to clean the old points when possible since the newer ones aren't made as well. I take the points apart and hone them on a succession of course to fine stones, finishing with a very fine hard arkansas stone and then clean them well. I'm confident they are better than new.

I'd say the condenser does just the opposite of smoothing the spark out. It helps the spark voltage start and stop cleanly.

David, The spark is produced by the collapsing of the magnetic field through the coil secondary windings. The points are the "switch" that turns on & off the current flow through the coil primary that makes this happen. When the points open, current flow stops and the magnetic field collapses inducing voltage into the coil secondary winding. The condensor is parallelled across the points. Their primary function is to provide a low resistance path for the current flow when the points open. Otherwise, the current flow will arc across the points to ground causing them to burn & pit.

Just to add to the previous posts, think of the condensor as a small rechargable battery. When the points are closed, the condensor is discharged (shorted out), when the points open the capacitor (oops condensor) charges on a logarithmic curve. This means that it takes the initial surge at the moment of points open and sucks it off the points, thus saving them from arcing.
Someone made a comment a short time ago that many coils get replaced that are not bad. I would put the condensor in the same catagory.
It's not altogether a bad thing to swap out the parts sometimes just to be sure we've licked the problem, but in the case of a costly mag coil, testing is in order.
i'm kicking my butt now because an original style coil for my 50 was lying in the dirt when i picked up the tractor and i failed to grab it. good chance it was still good.

I am sure it is a reproduction coil, but Wengers of Myerstown, PA has coils available for $43 (see: http://www.wengers.com/parts/parts_deta ... =352355R/N )

Is this the correct coil? It seems to match the part number in the parts catalog. I also checked Columbia Tractor, and another IH dealer in the same area, and they both had coils for about $60. Is this more like the normal price? Seemed expensive to me.

David

David:

Ifn you think $60.00US is expensive, come up here and try to buy it for that. New from CaseIH (who is the only one who can get it ), we have to shell out $125.00 Cdn plus 15%HST of $18.75, which brings it to a grand total of $143.75.

Now that is expensive

That is why I am using a UC12 external 6Volt coil which cost me a grand total of $12.00 plus HST = $13.80. I am going to have to save my pennies to get one of the proper ones for the restore. It will be a while!