Starting Problem with a 300

Siefring Red Farmer · Mar 28, 2010

I have a 300 that will start most times, but not always. When it won"t start, I disconnect the center wire to the ignition coil and crank it over. As it cranks, I cause it arc to the coil and then it will immediately start. Why is this and how do I fix it. I have converted to 12v and have an electronic ignition installed, though it did this before the conversion.

Janicholson · Mar 28, 2010

Interesting. You are lucky it is still working.
But the reason it fires is important.
Most electronic ignitions will fail promptly, or arc the inside of the coil when allowed to operate with no path for spark to go. (pulling the wire out!)
Reason is that the process you describe raises the spark voltage to about 25000 volts or more. As the wire gets into contact this serious voltage will jump the spark plug gaps with more energy and ignite the fuel and air starting the tractor.
Fix it by putting in new plugs gapped to .045" and it will be fine. I like Autolite, or Motorcraft plugs. Jim

Anonymous-0 · Mar 29, 2010

I would have to look at my manual....045 is way too much. Most IH systems back then were around .030 or so.
If you have a strong battery...check and insure the cables are good. Look for corrision under the outer coating near the terminal. If all that is good...sounds like a weak coil.

rustyfarmall · Mar 29, 2010

(quoted from post at 10:53:25 03/29/10) I would have to look at my manual....045 is way too much. Most IH systems back then were around .030 or so.
If you have a strong battery...check and insure the cables are good. Look for corrision under the outer coating near the terminal. If all that is good...sounds like a weak coil.

The specified gap is 0.025", but by increasing the gap to 0.045", the voltage will need to rise in the coil, thus resulting in a hotter spark which will aid in starting, but I can't help but wonder if there isn't something else ailing with that engine. Maybe the compression is way low?

Anonymous-0 · Mar 29, 2010

Sounds lazy...but the way I always did it...if it acted that way, I would ask dad to give me a tow. If it started in a few feet...usally something was dragging the start voltage down.
Those 300 starters were not the best with.

Janicholson · Mar 29, 2010

With electronic switching (as in post) there should be no issue with .045 (a hot coil might help, but the existing coil is working (if the wire is pulled out!)

Starting Problem with a 300

Siefring Red Farmer

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Janicholson

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Anonymous-0

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rustyfarmall

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Anonymous-0

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