1950 Cub- No Spark

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IHCubCadet147
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1950 Cub- No Spark

Postby IHCubCadet147 » Tue May 23, 2023 9:28 am

I’m trying to get my new to me Cub running. The PO said it ran when he parked it about 5 years ago, in a barn. Now it has no spark. First I tried cleaning the points, nothing. They were corroded along with the other contacts in the distributor. I ordered a tune up kit with points, condenser, plug wires, distributor cap, rotor, and new spark plugs. Put it all in and set the points to 0.020, still nothing. I read through a bunch of old posts on here, and tried everything I could find. There is power from the switch to the coil. There is no power from the coil to the distributor, but if I disconnect the wire from the distributor, then there is power coming out of the coil. From what I read, this means my coil is good, and there is a ground in the distributor. I put a new insulator in, although the old one didn’t look like there was anything wrong with it. I also put the old condenser back in to try it, thinking the new one might be bad. According to a test I found online, both condensers are good. At this point, I’m out of ideas. Any help would be appreciated. I’m not great with electrical problems, but with some directions, I can use a Mulitimeter or test light and usually figure things out. It’s probably (hopefully) something simple that I am missing.

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Re: 1950 Cub- No Spark

Postby Eugene » Tue May 23, 2023 9:39 am

IHCubCadet147 wrote: There is power from the switch to the coil. There is no power from the coil to the distributor, but if I disconnect the wire from the distributor, then there is power coming out of the coil.
Short inside the distributor at the insulator.

Common mistake. The condenser wire and or points spring installed between the insulator and the distributor case. Both are installed with the insulator next to the distributor case and then with the condenser and points on top.
I have an excuse. CRS.

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Re: 1950 Cub- No Spark

Postby Jim Becker » Tue May 23, 2023 10:34 am

Reconnect any wires you have disconnected. Verify that the points are closed. Repeat your voltage tests and you should find voltage on the switch side of the coil and no voltage at the distributor side of the coil (as you found before). Now, manually rotate the engine until the points are open. Repeat the voltage tests. You should find voltage on both sides of the coil. If so, you do not have a stray ground inside the distributor and you need to look for some other problem. If you do not have voltage on the distributor side of the coil, there is a stray ground caused by the wire to the distributor or inside the distributor. The stray ground could be in the connections, for example as Eugene described. It could also be a bad set of points that are shorting themselves or even a bad condenser.

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IHCubCadet147
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Re: 1950 Cub- No Spark

Postby IHCubCadet147 » Wed May 24, 2023 6:46 am

Eugene wrote:
IHCubCadet147 wrote: There is power from the switch to the coil. There is no power from the coil to the distributor, but if I disconnect the wire from the distributor, then there is power coming out of the coil.
Short inside the distributor at the insulator.

Common mistake. The condenser wire and or points spring installed between the insulator and the distributor case. Both are installed with the insulator next to the distributor case and then with the condenser and points on top.

That is how it is installed, and I also made sure the points spring and condenser wire are not touching the case anywhere.

Jim Becker wrote:Reconnect any wires you have disconnected. Verify that the points are closed. Repeat your voltage tests and you should find voltage on the switch side of the coil and no voltage at the distributor side of the coil (as you found before). Now, manually rotate the engine until the points are open. Repeat the voltage tests. You should find voltage on both sides of the coil. If so, you do not have a stray ground inside the distributor and you need to look for some other problem. If you do not have voltage on the distributor side of the coil, there is a stray ground caused by the wire to the distributor or inside the distributor. The stray ground could be in the connections, for example as Eugene described. It could also be a bad set of points that are shorting themselves or even a bad condenser.

Nothing is disconnected. There is no voltage on the distributor side regardless if the points are open or closed, unless I disconnect the wire from the distributor. I don’t see anything touching metal that shouldn’t be. I didn’t think about the points being bad, maybe I’ll put the old ones back in and try it.

BEF32E1E-E012-47C3-A587-FC54CB252E6A.jpeg

Eugene
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Re: 1950 Cub- No Spark

Postby Eugene » Wed May 24, 2023 8:44 am

Continuity test. Points open, from distributor wire connection to the distributor housing. Test the condenser. Points spring touching distributor housing?
I have an excuse. CRS.

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Re: 1950 Cub- No Spark

Postby tst » Wed May 24, 2023 8:58 am

clean the points plate up , looks crudy, can cause bad ground for the points

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Re: 1950 Cub- No Spark

Postby Jim Becker » Wed May 24, 2023 10:16 am

Disconnect the wire from the coil at the distributor. Attach an ohmmeter between the lug on the side of the distributor and ground. Turn the engine as needed to open the points. At this point, the ohmmeter should show an open. But based on your descriptions it will show zero or very near zero. Now you can start eliminating possibilities inside the distributor until the fault goes way. I would start by unscrewing the condenser bracket so the condenser is not contacting ground. If there is still a short, fiddle withh the points a bit to see if it interrupts the short. If still a short, take the nut off the inside of the stud so the condenser wire can be removed. If still a short, remove the points. If still a short, the stud is grounding. Whichever part you fiddle with or remove that eliminates the short is the part that is either defective or improperly installed.

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IHCubCadet147
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Re: 1950 Cub- No Spark

Postby IHCubCadet147 » Wed May 24, 2023 3:11 pm

Eugene wrote:Continuity test. Points open, from distributor wire connection to the distributor housing. Test the condenser. Points spring touching distributor housing?

I think that is what I did, both condensers tested good.
tst wrote:clean the points plate up , looks crudy, can cause bad ground for the points

I will do that.
Jim Becker wrote:Disconnect the wire from the coil at the distributor. Attach an ohmmeter between the lug on the side of the distributor and ground. Turn the engine as needed to open the points. At this point, the ohmmeter should show an open. But based on your descriptions it will show zero or very near zero. Now you can start eliminating possibilities inside the distributor until the fault goes way. I would start by unscrewing the condenser bracket so the condenser is not contacting ground. If there is still a short, fiddle withh the points a bit to see if it interrupts the short. If still a short, take the nut off the inside of the stud so the condenser wire can be removed. If still a short, remove the points. If still a short, the stud is grounding. Whichever part you fiddle with or remove that eliminates the short is the part that is either defective or improperly installed.

Didn’t think about that, sounds like the best way to find the problem. I will do that and report back.

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Re: 1950 Cub- No Spark

Postby Glen » Wed May 24, 2023 3:15 pm

Hi,
I'm not sure if you are having this problem with the points, but here is some info.

They have said on here that some new points for Cubs come with a clear coat on them, to prevent corrosion, I guess. Power doesn't go through the clear coat. Try using a point file and filing the points, that should remove the coating, if it is there.
Wipe them with a clean rag when done filing.

Also put some clean motor oil on the felt in the end of the shaft the rotor goes on, I can see it in your pic above. The operator's manual says to oil there.
Then put the rotor on, and turn it back and forth, it should turn slightly. The shaft has to turn slightly so the spark advance works right.
If the slot on the screw holding the one point is getting so it is hard to keep the screwdriver in it, TM Tractor Parts has a new one. Below is their listing. :)
http://www.tmtractor.com/new/el/7263fp.htm

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IHCubCadet147
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Tractors Owned: 1950 Farmall Cub
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Sears SS/16, Massey Ferguson 7

Re: 1950 Cub- No Spark

Postby IHCubCadet147 » Tue May 30, 2023 6:03 am

Thanks for the help guys. Not sure exactly what I did, but it now has spark, and runs. Apparently the last time I was messing with it I had fixed it and didn’t even know it lol. I hooked an ohmmeter up as Jim posted above, and it showed an open. At first I thought I was doing it wrong, but I pulled a plug out and grounded it and it had nice blue spark. I hooked up my temporary gas tank, and it stated right up! :{_}:

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Re: 1950 Cub- No Spark

Postby staninlowerAL » Tue May 30, 2023 9:40 am

Not bad for a 70+ year old tractor! IMO you are experiencing what is so interesting about these machines. Now that you have it running you can expect to find more challenges as you come to know it better. The more problems you discover and solve, the more confidence you will have in the everyday use of it. Congratulations on your success!! JMHO Stan
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USAF & Reserves, Reg ARMY, ARMY NG (AL)


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