450 won't stay running

ChasK · Nov 8, 2013

My farmall 450 is a 12 volt negative ground system.
The alternator has a light. I've never had any problems
the past years. After sitting for a month I tried to start it.
It will only stay running if i hold the starter button down.
What am i needing to look at?

Anonymous-0 · Nov 8, 2013

Jump across the little white resistor on top of your coil and see if it keeps running.

ss55 · Nov 8, 2013

I agree with Grand Prairie Waterloo, it sounds like low coil voltage after the starter button is released. A bad coil resistor is the most likely problem. Low battery voltage and corroded connections might also contribute to the problem. Either way, I would fully charge the battery if it has been sitting a month in cold weather.

old · Nov 8, 2013

There is a number of things that could be wrong.
What I would do is hot wire it. Hook a wire to the ignition side of the ballast resister and start it. If it stays running that way you problem is from there back to the battery as in bad wire or bad switch. If it does not stay running then it is from there forward.
Next thing to do is check for a good blue/white spark that jumps a 1/4 inch gap. If you have that then
Pull the carb drain plug and make sure you have a good steady flow of gas for say 3 minutes. Catch the gas to look for water dirt etc

ChasK · Nov 8, 2013

I got a chance to look at it in the daylight this afternoon.
Turns out there was a wire off the resistor.

Thanks to you guys I knew right where to start looking.
Guess I'll get some rock hauled up now!!

Thanks again!

jimg.allentown · Nov 8, 2013

This is how it works on paper:
Due to voltage drop while cranking the engine, the voltage to the coil also drops. This causes a weak spark that may not be sufficient to start the engine. To remedy this, we use a lower voltage coil that will provide a nioe hot spark at cranking voltage. Once the engine starts, and the starter load on the battery is removed, voltage rises. To accomodate this, a resistor is used to drop the voltage back to the cranking voltage AT THE COIL.
To accomplish this, the start button or key switch has a circuit that BYPASSES the resistor during cranking.
So, when you are holding down the starter button, the resistor is bypassed and you have spark to start the engine. When you release the button, the circuit is broken, and the engine stalls because the resistor is probably burned out causing the broken circuit.
Surprisingly, these resistors take a lot of stress while in operation, and are a relatively common failure, but not as common as I would have expected.

450 won't stay running

ChasK

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Anonymous-0

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ss55

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old

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ChasK

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jimg.allentown

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