Another 300U electrical questions

Dave H (MI) · Apr 20, 2015

So, yesterday I am checking for spark before running out for some new plugs and one of the kids had a crisis and I forgot to turn the key switch off before running off to aid the victim. Pardon my sarcasm, but it was not a crisis and there was no real victim...but I digress. Then headed off to the store to buy the plugs. Stopped off at the farm to show the wife some equipment I picked up at auction Saturday. Had dinner. Hours later I discover my error. Battery is dead. So I left it to charge overnight. Today there is no spark. Yesterday there was spark. To make a long question a little longer...am I likely to have burned up my coil or some other part of the electrical system? It's raining off and on today and it's hard to get out there and check anything as it is tarped pretty good.

I am a little PO'd at myself.

John T · Apr 20, 2015

1) First thing Id look at is the points to see if they are badly burned or pitted or all carboned up. If so a good cleaning or light filing may cure them, but Id be looking for a new set of points.

2) The coil could have overheated and the LV primary opened up. Check for continuity from the little + and - terminals to see if there is around 2 to 4 ohms and NOT an open circuit. Likewise, if you turn the ignition ON and place a voltmeter or test lamp on the coil, with the points open (or just remove wire from coil down to distributor) there should be a light and voltage on BOTH the + and - terminals.

3) There could be a problem in the wiring from ign switch down to the coils input. See if a test lamp glows on the coils input when ign switch is turned on.

4) If it had an ignition ballast resistor it may have overheated and opened up.

If its none of the above, work through my Ignition Troubleshooting Procedure linked below to determine the cause of no spark.

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition Troubleshooting

old · Apr 20, 2015

Coil is probably find but the points will be burned but may still be able to file them and get by for a long time. Pull the distributor cap off and use a screw drive in the points area and if you get a spark off the screw drive but do not get one when you open the points they are burned and need cleaned

Dave H (MI) · Apr 20, 2015

Alrighty...much appreciated! I'll check it out when the weather moves thru.

CNKS · Apr 20, 2015

I did the same thing to my 300U, coil was hot, battery dead. Started easily when the battery was charged.

Dave H (MI) · Apr 20, 2015

If only!

87nassaublue · Apr 21, 2015

Yea, what the other guys said. Start with the points and go from there.

Another 300U electrical questions

Dave H (MI)

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John T

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old

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Dave H (MI)

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CNKS

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Dave H (MI)

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87nassaublue

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