Super A Erratic when warmed up

steve706 · Sep 11, 2017

My Super A (12 volt conversion) starts to run extremely rough after running for 15-20 minutes to the point of surging or shutting down. Sometimes it sounds like a miss with hesitation or borderline backfire. Starts up and runs perfectly, no problems at all until a certain time is hit, then downhill from there.
I have gone through previous threads and still can't figure out issue, am guessing it is something obvious I am overlooking.
Points, condenser are good
Fuel flow to carb is good
All electrical wiring is good
Ignition coil was replaced in spring
Ballast resistor good
Spark plug wires good

Any ideas would be gladly appreciated,

parisspringstom · Sep 11, 2017

I am always suspicious of condensors and would change it out with another one. They can be faulty even when bought new.

gene bender · Sep 11, 2017

I would fins an old condenser and try that onebefore getting a new one

old · Sep 11, 2017

Stop guessing and do some simple trouble shooting. Fire it up and run it till the problem start then trouble shoot it.
#1 check that you have a good blue white spark the jumps a 1/4 inch gap or more at the coil wire and at the plug wires. If the spark is weak try a hot wire from the ignition side of the battery to the ignition side of the coil. If it run right that way the problem is from the coil back if it does not help it is the coil or condenser or wires breaking down.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fil la pint jar in under 3 minutes. Yes catch the gas to look for water and dirt.

steve706 · Sep 11, 2017

I have already done everything you have said, not guessing, that's how I know all the parts I listed are good.

steve706 · Sep 11, 2017

Already tried a condenser off another Super A, no luck, problem still the same.

MikeJM · Sep 11, 2017

Like old asked, how long does the fuel run well to the carb? Have you check the gas cap? Sometimes the vent gets clogged and it'll start and run fine, few minutes in and it loosing power and carrying on.

old · Sep 11, 2017

You could also have a problem like I had on my BA which is the front half of a B and the back half of an A. But any how it would run fine then all at once died and then wait 5 minutes and it would start up again and work fine for a while. I found it had some leaves in the gas tank and it would suck the leaves down and died then when the carb did not need gas the leaves would float up again and it would run till it happened again

steve706 · Sep 11, 2017

Fuel runs in continuous steady stream, drained a gallon with no interruption in flow. Gas cap is good, been switched out already,no difference.
Good ideas though.

old · Sep 11, 2017

Is that gas flow out of the carb drain plug or the fuel line?? What about the air cleaner?? When was the last time it was checked and the mud and water dumped out of it and good oil put in??

Janicholson · Sep 11, 2017

Was it running good between now and spring? New coils can be bad. Was the old coil replaced because of this problem? Feel the coil when the issue happens, if it is way hot that is the problem, new or not. Jim

Charlie M · Sep 11, 2017

Maybe a leak in the manifold or the gasket at the manifold for the carb. Is it old manifold. If you give it a little choke does it run better?

mite-help · Sep 11, 2017

what old said about the leaves---had one like this, passed all the fuel flow tests, [at the moment it was checked only way I found was to hook up a different fuel supply-[large lawnmower plastic tank]

steve706 · Sep 11, 2017

Have done drain from both carb and fuel line, both steady. No water in air filter cup, oil is still clean as well.

steve706 · Sep 11, 2017

Happened in the past on the rare occasion and the last coil was changed because it went bad. Already took one off another tractor that is good and still occurred.

Steve@Advance · Sep 11, 2017

A couple things to check...

The new coil. Take the wires off the terminals, check across them with an ohm meter.

If you get around 3 ohms, that coil is designed to run on a 12v system without a resistor.

If you get 1,5 ohms, that coil needs a 1.5 ohm resistor in series with the + terminal.

Regardless what the coil may say on the can, best to check it. If it needs a resistor, it will overheat the coil and burn the points. If it doesn't need a resistor, and there is one in the circuit, you will have very weak spark.

Another thing to check is side play in the distributor shaft. If any play, the points will not stay set, and can change with varying RPM and temperature. Once points are run out of adjustment, that can be arced and will not make good connection. The quality of today's points is bad. Might consider a Pertronix conversion.

Hobo,NC · Sep 11, 2017

Try straight wiring it (bypass the ignition switch) Cost pert near nuttin to try... On one of my farmalls it drove me crazy shutting off pop'N ETC I just happen to be looking at the voltmeter and it shut off the voltmeter jumped :idea: Dagumm cheap switch :evil: was the culprit..

Gene Davis (Ga.) · Sep 11, 2017

Working on a 3 yd Libeherr track hoe some years ago and had a problem like that. When it stopped I finally got to it and took loose the fuel line to the transfer pump and it had no fuel. Started taking it apart and when we emptied the fuel tank there was an acorn stuck in the fuel outlet. Maybe it fell in when someone was refueling it?

Janicholson · Sep 11, 2017

Try to move the distributor shaft sideways and up and down. If it is able to move visibly, it is too loose. .001" is about all that can be tolerated. If worn, the timing and point gap change radically. Jim

Anguspg · Sep 12, 2017

when it starts running erratically , have a timing light hooked up and observe the timing mark to see if it's moving off its marks.

Super A Erratic when warmed up

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