JD 420 Stops Running ..Sometimes

Emmo

Member
I have an old JD 420 (1950's), 2 cyl, 6 volt system. All I use it for is to bush hog around the barn and lanes and to plow and disk a small garden. This summer it has started dying after using for usually 30-45 minutes. It doesn't always do this, it's very random. It does seem to happen usually after running for some time. Sometimes it dies and I have to re-start and sometimes it will start to die (just like the key was turned off) and if I shove in the clutch it will start running as normal. When it dies completely, it usually will start right back up, one time I had to wait 5 minutes before it re-started. This past weekend I bush hogged on Saturday for 45 minutes and it had ran fine and then started to die. I shoved in the clutch and turned the key off and right back on and it started running OK. I was done bush hogging so I took it to the barn. Sunday I started to disk the garden and after just 10 minutes or so of running and disking it started to die. I did like Saturday and shoved in the clutch and switched the key off an on. I did this several times and for a minutes or so it just set there running, but missing. Finally it began running ok, so once again I took it to the barn. When this first started happening, I thought it might be fuel related. I cleaned the carb and sediment bowl, but didn't see any difference. I'm no mechanic, but would appreciate any thoughts or suggestions you can offer. Thanks
 
My MT was doing something like that and missing a few years ago. It was missing more than it was trying to stall out. I did a rebuild on the ignition system. Cap, rotor, condenser, points, coil, solid core plug wires, new plugs. I cannot say exactly what part fixed the issue but the tune-up fixed the issue and tractor ran great. I also used a timing light to adjust the distributor and got the timing dead on. It was a few hours work. It almost took as long to source all the parts. Cost about $250.

Maybe someone else will chime in as to how the clutch plays in but the missing leads me to believe its an ignition issue myself.
 
Thanks hotflash and rla, the missing only occurred the one time and that was Sunday. Always before, it was just like the key was turned off. However, almost any reaction by me would keep it running, shovel in the clutch, switch on and off the key or pump the throttle. This has happened maybe 10-15 times or so this spring/summer and I think it only died by twice. The other times it would either start to die and then catch and take off on its own or I would do something which may or may not have had any impact. Thanks again.
 
Agree with both [b:654c4848f0]rla[/b:654c4848f0] and [b:654c4848f0]hotflashjr[/b:654c4848f0] about replacing the condenser.

We have 3 tractors that have had issues with failed condensers.

All have "acted" as you described above, but engaging the clutch never helped them.

Start by changing the condenser.

While you have the distributor cap off, check the two contacts/terminals for wear.

Take a look at the photo below.

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The distributor cap shown above came off another MT that died as if the ignition had been turned OFF.

Replaced the condenser, but still would not start.

No spark at the plug, so "swapped" spark plug wires with another tractor and still would not start.

Replaced the distributor cap and it started and still runs great two years later.

Hope this helps.
 
I had the ignition switch go bad on my 430....time didn't matter though, would cut out completely at random.
 
my money is on the ignition switch. I had a 420 that would die randomly like you shot it.

As I recall you can jump a wire from the lug on the starter straight to the coil and bypass the ign switch. i ran mine like that for a while until the new ign switch came in.

Condensers, i don't know. I never change one for grins, they seem to be either good or bad. I remember a new bad one that frustrated me.
 
Thanks everyone for all the input. I think I'll start out by cleaning the connections on the switch panel, checking the inside of the distributor cap and changing the condenser. I'll see if those help.

This tractor is getting pretty old (1956), though it's not quite as old as I am. It belonged to my dad and as long as I can remember, he had a John Deere 420. I suppose it's got a home on the ole farm as long as I do, even if it is starting to get a little ornery! Thanks again everyone, your help and advice is very much appreciated.
 
another vote for the ignition switch.
My 420 does that, completely random, I know what it is, so I just reach down and wiggle the switch, or click it to another position.
......I probably should fix it...I'll get to it.....
 
A quick update, I changed out the condenser, points and plug wires this morning. The points looked very worn and were barely opening. Tractor started, though it was much harder to start than before. Once it started it ran good until I hooked to the disk and made a round in the garden. It started the dying and missing routine. I unhooked the disk and took it back to the shade for more tinkering. To get it back to my work spot I had to keep turning the key off and on. I tried to take out the switch, but the nut was frozen. I'll take some penetrating oil over tomorrow and see if I can get a better look at the switch. Maybe I can figure which wires to connect to pass the switch. That would identify the switch as the problem or rule it out.
 

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