1961 Cub Cadet Original - spark only when cranking

[Janomat 3000]

Hello,

first of all i want to introduce myself. I live in Germany and i am a new owner of a lovely Cub Cadet Original with Kohler engine and Delco starter generator.

After changing the brushes of the Delco starter generator the tractor was running without problems, but then had a ground brush wire.

After checking the inner cables i can't get the engine running again, i have only spark while pushing the starter button and cranking the engine. When i release the starter pushbutton engine has no spark and stops immediately.

I can't measure the output of the Delco unit, because my multimeter reads 12v only when starting, but that is from the battery.

Any ideas what is here the culprit, the generator itself, or maybe the voltage regulator? What can i do now?

Thanks for your help!

Jan

[ol'George]

With the switch in the run position, you should have voltage at the ignition coil.
if not, follow the wire back to the ignition switch where it should get its power from.
its a really simple electrical system.

[Janomat 3000]

Thanks George for the reply.

I know there are not many cables on this tractor and electrical system is really simple. My problem is, that the tractor is located at my holiday home in Spain so i can't measure anything at the moment, but i don't get any parts there and want to have everything with me on my next visit.

So i would be really thankful if i could get the defective part now and install it on my next visit.

So is there a diagnose for the most possibly failed part when spark is there, but only during starter cranking? I already checked ignition switch, starter button works, and voltage at the coil should be there because spark is there when i turn the starter on battery power.

Any ideas which part could cause this problem?

Thanks to George and all other members that chime in with helpful hints!

Best,

Jan

[ironman]

So assuming your Original is wired as shown in this drawing....
You say you turn your key switch to on, then push the starter button.
You say the engine attempts to start, but dies when you release the starter button.
You say you see spark only when pushing the starter button with the key switch "on".

As you can see in the drawing, the gray wire delivers constant battery voltage to the "B" terminal on the V/R.
When you push the start button, battery voltage is delivered to the S/G's "A" terminal and simultaneously to the "G" terminal on the V/R via the blue wire.
The battery voltage on the V/R's "G" terminal supplied from the start button should operate a relay inside the V/R that connects the V/R's "B" and "L" terminals, and puts battery voltage on the "B" terminal.
The battery voltage on "B" is now sent along to "L" and thru the green wire to the key switch, then via the black wire to the coil if the key is in the "on" position.
Once the engine is running and you release the starter button, the S/G produces the voltage to keep the relay inside the V/R operated, the "B" to "L" connection is maintained and voltage is sent along to the coil.
I think the key switch and starter button can be eliminated as suspects.

Since you are getting spark when the starter button is pushed, the "B" to "L" connection inside the V/R must be happening but doesn't remain once you release the starter button.

So it would seem that either you have a faulty V/R because the relay is not remaining operated with voltage supplied from the S/G....
OR....the S/G is not supplying voltage to the V/R.

What troubles me is from you opening post, you say
"After changing the brushes of the Delco starter generator the tractor was running without problems, but then had a ground brush wire."
You didn't elaborate on any details of this incident, the circumstance, the cause, the fix. Obviously it was important.
A "ground" in any electrical system, where it's not supposed to be, can cause multiple problems so it's impossible to give you accurate advice from thousands of miles away.

What you can try to narrow things down would be to connect a jumper wire from your positive battery terminal to the positive terminal on your coil.
That should give you constant spark and get the engine started.
Once running you should be able to make some voltage tests to see if the S/G is producing.

Also, make sure that your V/R has a good clean connection to frame ground, and all your wire terminals are clean and tight.

Not much help but it's a starting point.

[Janomat 3000]

Hello,

and thanks for this detailed and also very helpful post! When i'm visiting my holiday home in the middle of june i will check what happens when i use a jumper cable to supply constant voltage to the coil. And i'm thinking of taking a new regulator with me, if that is the culprit i can have the tractor running again and the V/R is probably not too pricey.

Does anyone have part numbers for the Delco starter generator and the voltage regulator for me?

Thanks a lot for your help!

Jan