Super A Quits When Hot

Super a quits when hot.
Runs fine until it quits.
12v
Already:
Changed coils (thrice)
Points, condensor, plug wires, spark plugs.
Serviced air filter (oil).
New inline fuel filter.
Service fuel bowl (removed screen)
Flushed radiator.
Cleaned outside fins of radiator.
Fresh fuel.
Charged battery.
Checked primary voltage...ok.
Removed Zenith carb, disassembled and cleaned Ino kit).

Strange thing is it starts and runs great...until it is hot and working.
Then it does a couple of quick burps and quits like you shut the key off.
5 minutes laster it starts fine.
My gut says coil, but after the third I was slapping myself not to go there any more <g>
Really scratching my head.
Need sane mine to offer suggestions.
Thanks ahead of time from hot SE Geaorgia.
JeffR


It runs gr

Sure does sound like coil. HAve your replacements all been either straight 12v coils or 12v requiring a ballast resistor?

Aslo wondering if, with the inline filter, you might have some unconventional routing of your fuel line that might be making for a vapor lock?

Remove the inline filter and replace with a piece of gas line tubing and see what happens.

Does it have a external resistor by the coil, or a coil with a internal resistor? A 12 volt system MUST have a resistor. Also, get rid of the in-line fuel filter, they can cause problems and you don't need one. The sediment bowl and carb screen filter good enough.

Sounds like vapor lock to me. Check your fuel line routing for getting to close to the engine or especially the exhaust. While you're at it, check the fuel tank to be sure it is clean and not full of trash that might be getting sucked over the fuel pick-up regularly.

When it quits pull one of the plug wires & check for fire to your plug, do this asap before it cools. If there's no fire replace the condenser.
If it keeps quitting you need to make sure battery voltage is still getting to the coil. Use a test lite or volt meter & with the points open you should have voltage on both small terminals on the coil. If you have fire to your plugs you have a fuel problem. Look in the tank with a good flashlite to see if any rust or dirt is covering the outlet. Pull the gas line at the carburetor and see if there's a full stream of gas there. If that looks ok check behind the tube fitting where your gas connects and see if there's screen behind it that may be full of crud blocking the fuel flow. Hal

Jeff: Heave the inline filter over the nearest cliff. Restore the gas line and sediment bowl with screen to factory specs.

There is one other item, if the problem is fire to the plugs. Your distributor shaft could be worn and needs rebuilding. If this is the case tractor will usually stop when you hit a bump or other type of jolt. It doesn't have to be hot on this one. It happened to my 130 about 20 years ago, I'd get jolts when plowing snow or hitting a pothole on a gravel road, bingo she would stop, but fire right up immediately.

And put the screen back in the sediment bowl.

The ignition switch can go bad and when warmed up fail to conduct!
Hot wire from the bat to the coil (or ballast resistor if it has one) and see if it keeps running.
The other suggestions are also on target! JimN

Just thinking of causes of over-heating--is the fan belt in good shape---is the fan turning easily-bearing not dragging? You said that the radiator fins are free of dirt & air moves freely through the radiator? Maybe a radiator hose has a piece of the inside rubber coming loose & blocking coolant flow? Is the timing set correctly? How about the valve lash---set to specs?

We never had a SA--does it have a water pump? Possibly a bad bearing in the pump--impeller came loose from the pump shaft?

Solved it.....
But here's what I did first (after all the stuff in the first post)...

Put a voltmeter on the supply side of the coil.
Ran the tractor until it did it's hiccup/quit thing.
Stared at the voltmeter looking for a dropoff.
Stayed at 12 volts the whole time.
(Had a jumper wire ready to try to see if it might be a bad ignition switch, as suggested above).
Finally told myself (for the eleventeenth time) that it is not electrical and went over to the fuel side again.
The only thing I had not tried was rebuilding the carb (no kit in hand)...
But I had already taken the Zenith apart and cleaned it thoroughly (without adjusting anything other than the idle mixture screw)...
Looked up the float setting for a Zenith in my Allis Chalmers service manual (because I have none for a Farmall)...
Set the float just a tick higher than it had been.
Fired her up and went out with it.
Ran the cultivator more than a mile with no problem at all.
Am going to get a carb kit and install it for good measure.
My supposition is a combination of a slightly low fuel bowl level coupled with the crummy gas we are being sold these days.
Thanks for the ideas. I really was scratching my head, and that says a lot.
Thanks all!
Jeff

Lets think about valves hanging up when the engine gets hot. Maybe you should try a small amount of top oil or other upper cylinder lube--diesel fuel?