MODEL 50 JD not running

pneslund · Oct 25, 2019

I have a problem with my 50, ran great one day, then tried to start it and it will only keep running if I keep the starter pedal depressed. I've checked the wiring, replaced the coil, put a new battery in it. Can someone tell me what's going on?

old · Oct 25, 2019

Not sure if it has some sort of ballast resister by pass or not but sure sound like the problem. One easy way to figure it out is simply hot wire it. Run a wire from the ignition side of the battery to the ignition side of the coil and see if it will fire up and run. If it will then you have a ignition switch or wiring problem

fixerupper · Oct 25, 2019

Remove the cap screws that hold the dash panel On. Be very careful because they can twist off. Pull the dash panel away a bit and look behind it for a ceramic resistor. I will bet there is one. If there is a resistor check the wires on each end for being loose or broken off. If one of the wires is off you found the problem. If the wires are good the resistor might be bad. Get a short insulated jumper wire with bare ends and jump between the two terminals. I have not had one apart for a long time so I do not remember if the resistor is easy to see or not. Then turn on your switch and try to start it. If it keeps running with the jumper wire in place the resistor is probably bad. If the resistor is easy to access and you are articulated enough you can hold the jumper wire against the two terminals with your fingers while you try to start it that way you can pull the wire away from the resistor while the tractor runs to see if it dies with the jumper wire off.

Lots of typing to explain a simple procedure! LOL

mijohn · Oct 25, 2019

your ballast resistor is burned out. Just had the same thing happen on my 520, but my problem started with a shorted starter switch. All the older Dodge pickup trucks had the same ballast resistor, and when they acted the same way when they burned out. They would start but would not run. Just about everyone who had a dodge at the time kept an extra one in their glove box. your resister should be up under the dash. with a flash light look at the dash support under the hood on the pully side. it should be a white porceline block about three inches long. let me know how you do. john

pneslund · Oct 25, 2019

I'm impressed with this forum already! I've gotten three good leads THANKS. I'll post the results as soon as I can get back to the tractor.

PJH · Oct 26, 2019

As the others said, this problem would ordinarily point to a bad ballast resister. I agree on that idea, but my JD 50 does not have the bypass circuit that feeds the ignition while the starter is running. My tractor is an early one - do the later 50's have the bypass circuit?

James Howell · Oct 26, 2019

"[b:654c4848f0][i:654c4848f0]My tractor is an early one[/i:654c4848f0][/b:654c4848f0]"

Take a look at the diagram below.

Note the black wire that is connected to the starter switch and ignition resistor.

Take a look at the photos below.

Note the side terminal on the starter switch.

Note the black wire connected to the side terminal on the starter switch leading to the ignition resistor.

Note the black wire from the starter switch connected to the "output" terminal on the ignition resistor.

When you press down on the starter pedal, 12 volt power temporarily goes directly from the battery to the ignition resistor and coil at start up.

Take a look at the diagram below.

If the ignition switch is [b:654c4848f0]ON[/b:654c4848f0], then once you release the starter pedal, the power comes from the ignition switch to the ignition resistor and coil.

The photos above are of "1011" our very early 1953 Model 70.

Hope this helps.

fixerupper · Oct 26, 2019

(quoted from post at 22:05:48 10/25/19) As the others said, this problem would ordinarily point to a bad ballast resister. I agree on that idea, but my JD 50 does not have the bypass circuit that feeds the ignition while the starter is running. My tractor is an early one - do the later 50's have the bypass circuit?

PJH I have it in the back of my mind the resistor started with the 20 series but like I said it's been so long since I have worked on a 50 I don't remember much about it. This problem sounds like a resistor. If not, what else can it be?

PJH · Oct 26, 2019

James, my 50 does not have the side terminal on the starter switch, nor does it have the black bypass wire.

55 50 Ron · Oct 26, 2019

If not a bad resistor then either the ignition switch is not on or it's a bad switch. BTDT

PJH · Oct 26, 2019

Jim, I agree that it sounds like a bad resister, broken feed wire, or maybe a bad ignition switch. Based on James Howell's post, I have to assume that my early 50 did not come with the bypass circuit, and I see that there is a serial number break for the starter switch in the parts book.

I re-wired it a couple of years ago and the old wiring looked to be original. There was no by-pass wire from the starter switch and the switch itself does not have a side terminal.

Interesting. . .

jwuertz · Oct 26, 2019

Are all resistors the same? in other words, will the same resistor work for both 6 and 12 volt system?

old · Oct 26, 2019

Most 6 volt systems do not use a ballast resister but many 12 volts did. Reason the 12 volt system had them was most coils where made for 6 volt systems not 12 volts system so a resister was added to drop the voltage to 6 volts.

The Ford N series with front mount distributor was a 6 volt system but he square can coil was more like a 3 volt coil so it had a theromister which as it ran the resistance of the ballast resister went up. That was so at start up the coil saw 6 volts but after it had run a while the coil was seeing closer to 3 volts

jwuertz · Oct 26, 2019

Thank you for that, So if I have a 12 volt system, is an additional resistor needed besides the one on the switch?

I am trying to piece an Lp 60 back together and wasn't sure.

old · Oct 26, 2019

It can depend on if it was a 6 volt system when new or a 12 volt. I think but not 100% sure it was a 12 volt system from the factory and if that is true you only need the resister that was there when new if of course it is still good

jwuertz · Oct 26, 2019

I think probably a 12v. It is a 54 JD 60 Lp.
Would the Lp models be different? There is one there But not sure ifit was added. thank you for your help!

old · Oct 26, 2019

Again not 100% sure a 60 was 6 or 12 volts when new. That does fall into the years where it could be either. But of course it could also be one that was converted to 12 volts and if that is so then yes the resister is likely to be needed

jwuertz · Oct 26, 2019

Thank you, I think I will do some more research. I have 2 tractors I can look at.
Hopefully that will shed some more light.

old · Oct 26, 2019

I have a 60 but it is parts only so I cannot look at it and know if 6 or 12 volts. One easy way to tell is the number of cell in the battery 3 is 6 volts 6 is 12 volts

jwuertz · Oct 27, 2019

Thank you Old, When I got this one, It did not have a batt, coil or dist.cap.
It did have 1 grnd. stap and bigger cable and an alternator. They said they were trying to get it to run also.
I did read in the parts book, a 6 v. coil was used for Lp models. It seems confusing, but will get there.

old · Oct 27, 2019

Since you say it has an alternator it is most likely to have been switched to 12 volts since 6 volt alternators are not common

jwuertz · Oct 27, 2019

I think it is 12 v. also.
I was reading in LP Gas Equipment SM 2015 that lp does require a 6 v. coil
Also additional resistor.

pneslund · Nov 11, 2019

An update, finally got the old 50 running. It took a new ignition switch, starter switch, and a rebuilt starter. I appreciated all the help!!! The tractor will probably outlast me!
Thanks

MODEL 50 JD not running

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