Hi All,
My ‘41 9N with a new TSX33 carb has been acting up on me after I run the tractor for a while, quits, and will not start again until I drain the float bowl, bleed the fuel line by undoing it from the carb, drain the line out. I have undone the sediment bowl, checked screen and fuel flow so many times, I wore out the cork gasket and got a new one. Fuel flow seems to be good. I checked the vented tank cap and that’s ok. I even tried to start the tractor with the cap off, still no luck. I even blew out the lines with compressed air. But, when I put the lines back together, it fires right up, with little or no choke, and idles smoothly. Something is not allowing fuel to flow freely at times. I am figuring that the screen in the tank may have stuff blocking it maybe. But, fuel flows freely. Only after I run it for a half hour or so it sputters and quits.

I checked the spark with my spark tester, and although looks somewhat weak, I attribute that to having a 6 volt system. The spark is still there showing on my spark tester, even during the non starting episodes that happen.

Sounds like you have a bad condenser, internally cracked coil, or a bad ballast resistor. 6v system will produce as strong a spark as a 12v system if all components are up to par. Any of these components go bad you will have the same problem regardless of battery voltage.

Having the OEM 6V/POS GRN electrical system will not cause a weak spark. You have other issues. Check for fuel flow at carb the second it sputters and stops. Be careful working with a hot engine - don't remove the fuel around a hot motor. If okay, it's a wiring issue. You don't need to keep blowing out the fuel line. Already been asked, so do you open the Sediment Bulb TWO Full Turns? Did you clean the 3 screens? The Carb brass elbow fuel & screen inlet screen is often neglected and can be a possible cause if plugged. Don't assume just because you have a 6V battery it is wired correctly for the 6V/POS GRN system. Have you ever left you ignition key switch ON when shutting down the tractor? If so, and points were closed, chances are you melted some tar insulation in Coil and when engine gets hot/warmed, up you lose that insulation and it can cause shorting out and stopping the tractor.

Thank you toolpro for your information. I have cleaned the screen at the carb elbow, and the sediment bowl screen, which I replaced that and the cork gasket. The tank screen and undoing the sediment bowl from the tank, and checking the tank screen, I have not done as of yet. I have looked in the tank with a small light, and little gas in there, could not see any stuff in there.

I did undo the fuel line at the carb when it was not starting, and fuel did flow out the line.

Also, check your fuel tank cap to make sure it has a vent. There are some with no vent that can prevent air from entering to replace the fuel used.

My cap is vented. Also makes no difference even with the cap off.

Although it might be clogged, the gas tank has a vent in it. There is a dome at the other end of the tank, almost in line with the filler cap that has a vent hole in it.

When you open the valve on the sediment bowl, are you opening it all the way?

Yes. I have tried opening the sediment bowl valve all the way open. No change.

Edit:

The new carb is a rebuilt original TSX33. Not one of those Amazon Chinese pieces of junk. It has been working
flawlessly for a few months up until a week ago, when started having issues.

Thank you for any advice. 🙂

How hot is it where you are? Possible gas is boiling in the fuel line preventing it from getting to the carb.

Hottest it has been is near 90° . Most days in the low 80s.

Had it happen to me twice. First time had bought fuel during a cold spell. About 10 days later was pulling a drag to knock down weeds working tractor as hard as it would work. No clouds, bright sun, 85 degrees in December. Second time I had removed fan belt to take to store to get a new one. They did not have one. Was going to farm to mow and almost got there. Had forgotten to put belt back on. Tractor "ran out of gas" but tank was nearly full. As soon as engine died radiator cap vented alerting me to my error.

As JMOR said, the in tank screen does not do much. But that reminded me of another thing that used to happen randomly running out of gas when plenty of gas in tank. The previous owner must have had a little helper working on the tractor, as the gas tank rattled when I got the tractor. Pulled out rusty nails, bolts, nuts, washers, bottle caps, and a plastic soldier, and a die cast truck (hot wheels?) from the tank. Flushed out quite a bit of rust but could not get it all. Tractor used to run out of gas at random with plenty of fuel left in tank. I carried a rubber hose and a flair nut wrench in the tool box so when that happened I could take the fuel line loose at the carburetor and blow the (presumed rust) back into the tank. Never collected much rust in the sediment bowl however. One day when I had the tank off for another reason and was draining out the remaining gas from the fill hole, a piece of a candy wrapper came out into the pan. That was what was plugging the main at random. After that never had that problem again.

Sediment bowl in-tank screen is not much of a screen, as trash can come over the top and plug reserve passages and does no screening for non-reserve/normal flow. I have had to clear seeds and small fibers from down inside the area. Can't be sure applies to your problem, but maybe.

Thank you for the pictures. I may have to inspect the tank better. Tried looking with small light to see
any trash in there. No luck. I will keep it in mind.