51’ cub no spark

7

79 Truckster

New member
This is my first FARMALL cub, I just bought it a couple days ago and have been trying to get it started. I got the starter to crank after messing with it for a while but it doesn’t have any spark. So, I checked for power at the coil by using a multimeter on the two leads towards the front of the cub. I didn’t see any voltage. I’ve read threads about this topic but I am confused on how the coil gets power. My cub has been converted to 12v and has a alternator. The battery seems to only be used to crank the starter as no other wires are getting any power from it. Any help? Thanks in advance.
 
Is it ready to start?
Oil pump primed? Fluids checked?

Your tractor has a magneto ignition , or a distributor ignition. That'd different coils for each.
I'm imagining a 6 volt ignition system could somehow be separate from a starter cranking system. At least I get the isolated starter part of it.

You might need to research an complete tune up.
And visit each component for condition and adjustment.

For example , your ignition points. One of multiple components. But unique in it's condition and positions needs.

What coil you have , and what volt ignition system will help in trying to figure what you have.
My guessing your 51 is like my 48 , or 53 won't be any assurance of accuracy.
Your coil under a cap on top and in front of your ignition cap where your plug wires go in?
Or is it an exposed round coil perched above the cap? If the round coil , we'll want to know if it's 6 or 12 volt. And if it has a resistor mounted near if a 12 ,or an internal resistor.

Magneto could be just as likely on yours. In which case your coils power source is the magneto. If so , make sure your stop switch is working right or else you might be grounding out the system to prevent spark. Which is what the switch is supposed to do when working right ,in the right position.
 
Thank you for the response! I am going to check fluids later today. All of the ignition looks stock except the alternator so I am assuming it is all 6v. The coil is mounted on top and a little towards the front of the distributor and has 2 threaded connections one positive one negative towards the front of the tractor. There doesn’t look to be and sort of external resistor. The only thing connected to the coil is a wire coming from the top of the alternator which is spliced and goes back to the kill switch. I’m not sure what I should inspect first. I gapped the point inside the distributor to .020 according to a 1950 manual. New cap, rotor, plugs, and wires.
 
Your explanation sounds like you measured voltage across the two lugs of the coil. Finding no voltage there doesn't really tell you anything. Try measuring voltage separately between each one and a good ground. With the switch on, you should find battery voltage at the lug that is connected to the ignition switch. If none, you have a problem in the wiring or ignition switch. If there is voltage there, you may find voltage at the other coil lug, depending on whether the points are open (see voltage) or closed (no voltage). Connect the meter then slowly turn the engine by hand to see if the voltage cycles on/off with 1/2 revolution of the engine. If voltage remains on, the points are not making a good contact. The points are either out of adjustment or need cleaning/replacing. If voltage remains off, you may have a bad coil, points are not opening, or something is grounded out at the points or the wire to the points.
 
Update I got it running, I ran a power wire from the battery to the switch and from the switch to the positive on the coil. What type of oil does the engine need? It has the right amount it’s just watery. Also, the idle fluctuates big time even when in gear and moving, how could I fix this? It seems like some sort of vacuum diaphragm actuating the throttle.
 
79 Truckster":9i0wslw8 said:
Update I got it running, I ran a power wire from the battery to the switch and from the switch to the positive on the coil. What type of oil does the engine need? It has the right amount it’s just watery. Also, the idle fluctuates big time even when in gear and moving, how could I fix this? It seems like some sort of vacuum diaphragm actuating the throttle.
Click to expand...

Internet being erratic again today....
As you found , coil needed some current to step it up and a way for the stepped current to go to ignition....

Now , shut the tractor off.
One thing at a time.
Your fuel/carburetor system , or your governor are possibly the surge source. Could be many things. Dirt. Varnish. Or more.
From a bad carb gasket ,a warped top, a sticky linkage, bad adjustment multiple place. And more.
Engine timing could be revisited.

Here's some reviewing for you while you cuss me for telling you to shut it off...
viewtopic.php?f=1&t=91765
 
Hi,
The Cub operator's manual can help you learn about maintenance that the Cub needs.

Below is the 1955 Cub operator's manual. The experts on here recommend people read it. It has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1.
It shows how Cubs originally looked in it. The lube section begins on page 14.

http://farmallcub.com/rudi_cub/www.clea ... index.html

This manual shows the electrical system that a 1951 Cub originally had.
Cubs made before mid 1964 originally had 6 volt, positive ground electrical systems.

The Touch Control fluid mentioned in the manual was changed later to Case IH Hy-Tran fluid. It is sold at Case IH dealers.

I would check or change all the oils before using the Cub. Using it with low oil in a gear housing can damage the parts in the housing.
There are 3 separate gear housings, with 3 separate oil levels to check, in the rear area of a Cub, the transmission, and 2 final drives.

The transmissions in Cubs commonly get water in them, from rain, or condensation inside the housing over time.

You said it has an alternator in a post above. A 1951 Cub originally came with a 6 volt generator, and a voltage regulator, mounted on a plate beside the gen.
Below is a page from the operator's manual, showing the gen with the hood off. It can help you identify what the Cub has.
An alternator is usually not as long as a gen.

http://farmallcub.com/rudi_cub/www.clea ... e%2050.jpg

The throttle on a Cub has a governor, that has weights inside it that turn, and controls the engine speed. The linkage has to be adjusted right so the governor works right. :)

I sent you a PM, they are at the top of the page.
 
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