Farmall 400 that only runs when starter switch is fully engaged.

   / Farmall 400 that only runs when starter switch is fully engaged. #1  

Dale Barrick

New member
Joined
Feb 1, 2016
Messages
6
Location
Hampton
Tractor
Farmall 400
Can someone tell me what I should look for? My 400 only runs if I have the starter switch fully engaged as if I'm trying to start it. As soon as I let off on the ignition, the engine stops. I replaced the ignition switch but this has not cured the problem. I checked the battery connections but this didn't fix it either.
Do I have a short somewhere or maybe a grounding issue? Could it be in the regulator or starter solenoid?
Any help on what to try next would be appreciated!
 
   / Farmall 400 that only runs when starter switch is fully engaged. #2  
Is this an issue that started, or did you acquire the tractor like this?
 
   / Farmall 400 that only runs when starter switch is fully engaged. #3  
I'm guessing on this.

When the ignition switch is in the start position the solenoid on the starter sends a full 12 volts to the coil for starting. When the key is in the run position the power to the coil goes through a resistor that lowers the voltage to about 8 volts once the tractor is running. This makes the points last longer.

So turn your key on and check with a test light to see if you have power to the resistor. If you have power there then check for power after the resister. If there is power before the resister but not after then the resister needs to be replaced. If there is no power before the resister then there is a problem in the wiring between the resister and the key.

I had this problem on a 300 that I fixed up. Turned out to be a poor connection in the wire terminal by the key.

If you need to move the tractor you can bypass the ignition switch by running a jumper wire from the positive on the battery to the positive terminal of the coil. The tractor will not turn off until the jumper wire is removed. Do not run the tractor for a long time like this or the coil will get too hot.

Hope this helps.
 
   / Farmall 400 that only runs when starter switch is fully engaged.
  • Thread Starter
#4  
I've owned this 400 for about 25 years and it's always been a reliable machine. It just started a couple of days ago.
 
   / Farmall 400 that only runs when starter switch is fully engaged.
  • Thread Starter
#5  
Great! I'll go check it out this morning and let you know what I find! I was able to move it to the machine shed so at least its out of the elements.
 
   / Farmall 400 that only runs when starter switch is fully engaged. #6  
Also called a ballast resistor. I agree with this being the culprit.
Jim
 
   / Farmall 400 that only runs when starter switch is fully engaged.
  • Thread Starter
#7  
I replaced the ballast resistor and the starting issue is now resolved! Thanks for everyone's assistance. The new resistor was not an exact replacement so I had to make a simple bracket to attach it. I also replaced some of the wiring and connectors while I was at it.

I have another issue that started recently. The 400 runs great while it idles and for the first 10 minutes but then I have to run the engine with the choke engaged in order to get enough fuel to keep it running. I've drained and cleaned the sediment bowl and fuel lines as well as drained the carburetor. It is also running rich as I see flames coming from the exhaust. I'm ready to purchase a rebuild kit and go through the carburetor.

Any ideas on how to correct this issue?
 
   / Farmall 400 that only runs when starter switch is fully engaged. #8  
Remove the elbow where the fuel line attaches to the carb. There is a fine mesh screen, or should be attached to it. Sounds like it may be partially plugged. Spray it with carb. cleaner from the outside, and flush sediment out. Ought to be good to go.
 
   / Farmall 400 that only runs when starter switch is fully engaged. #9  
yup, could be tank vacume, dirty tap, elbow, etc.

check those as mentioned.
 
   / Farmall 400 that only runs when starter switch is fully engaged.
  • Thread Starter
#10  
Okay guys, I'll go get a can of carb cleaner tomorrow and get cracking.
Thanks again! I'll keep you posted on the results.
 
 
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