IH 300U engine flooding Out

Does anyone have a problem with their 300U engine flooding out? I have a 300U that starts up just fine and will continue running until I shut the engine off or stall out. Then it will not start up again unless I let it sit for at least 15 minutes. If I keep cranking the engine before that time it will not start. I can see gasoline pouring out the drain hole underneath the carburetor, which I believe is caused by the engine is flooding out. I have to let it sit for 15 minutes or more to let the gasoline evaporate out of the engine. But what puzzles me is I don't understand why this would even happen. Is it possible my engine creates a vacuum when I shut it off which then sucks up gasoline and floods the engine?

Anyone have a similar problem? Or better yet...figure out how to fix it?

Could be a few things.
#1 air cleaner needs to be serviced badly
#2 Gas tank vent clogged so it builds up pressure in the tank which pushes to much gas into the carb.
#3 Main jet set to rich
And probably a couple other things like say you have some dirt/rust in the carb which does not let the float needle seat like it should

Yep.
I have been using a 300U for around 25 years, and after about 5 years my solution was to install a new fuel filter bowl and cutoff at the tank. That way EVERY SINGLE TIME I am ready to turn the tractor off, I just turn off the fuel and then the ignition after the engine dies from lack of fuel. I am a competent mechanic, and I about wore that carburetor out taking it off and replacing bits and pieces.
There is an additional caution that may or may not apply to you, for those that are playing along at home-
IH had a gas cap issue that is adequately discussed elsewhere, I won't belabor it here. The nature of the problem (inadequate venting) led to tanks being under pressure, such that removal of a cap in a hot tractor full of fuel could lead to a sudden gush of liquid fuel being expelled from the tank, the hazard of which you can imagine. Whenever I hear about a flooding problem, I am reminded of this, and the fact that a needle can only hold back so much pressure. Always worth a check. jt

Those old tractors will leak gas from the carb if you crank them much and they don't start. When you shut off the tractor and leave the gas turned on does it leak from carb anyway. If so then you have a carb problem, if not then the problem is somewhere else.

If it runs fine until you kill it or shut it off, does it crank over with good speed when trying to start it . Those tractors are notorious for slow cranking speed when engine is warmed up good. That is why so many are converted to a 12 volt system. Low voltage from excess current draw during hot cranking may be your problem. As far as gasoline coming out of drip plug, that is what the drip plug is for, to drain gasoline that has not been drawn up into engine during cranking. Slow cranking speed will cause the gasoline to be drawn from carb nozzle but not make it's way up into engie. . Now, on the other hand, if it starts dripping gasoline after shutting down and before you try to restart that is a fuel problem with needle & seat , or float or even possibly pressure in tank, which I doubt as when running the pressure in tank is lowered as the gasoline leaves, thus the need for a vented cap.

I did, i.e. exactly as you describe it. The tractor was used for snow plowing only for many years before I got it. Owner was no mechanic, hired someone to change oil or spark plugs as needed. Tank had lots of rust in it. I flushed it many times with a couple gallons of gas, letting the crude settle to the bottom between each flush. I recaptured the gas at the sediment bowl for re-flushing. Lines and carb were tank cleaned. There is a screen just as the fuel lines enter the carb. Once all clean, problem ended.
But I still dump and clean the sediment bowl once or twice a year.

I did convert my tractor over to a 12V system and a new battery with 700 cranking amps, so its not the slow start of turning the motor over.

I appreciate the comment on removing the carburetor on and off till it was almost worn out. I have done that too. I replace the parts with a new carburetor kit, cleaned the fuel line, tank and bowl. I have not replaced the bowl yet or take the tank off, because I'm just too lazy to go through all that work. Plus, gas flows into the bowl quite fast, even after it stalled or was shut off.

I loosen the gas cap to see if I would have a pressure lock. Still same problem.

The carburetor does not leak while running, nor does the bowl leak either. All good ideas and I'll try playing with your ideas this weekend...barring no rain.

Thanks

But, does the carburetor leak out of drip plug when shut off before you try restarting it. If not and it was running fine before you shut it off , forget fuel and start thinking ignition. Do you have a six volt coil with a external resistor or a straight 12 volt coil that does not use a resistor. Do you have a by pass system from starter solenoid to ignition coil. Is coil running hot.

We had one when I was a kid. You are not cussing
it enough while cranking it over! Seriously the guy a
few posts below is right, if not a sunny 70 degree
day they start hard. Get the vented gas cap for it.

Long ago on my 300U found the float not set correctly. It must be dead level with the top of the carb held upside down. Also look into the tiny spring that was sold to keep the floats from bouncing. My Cub carb has it and that might help too. Check the floats though.

All good suggestions. Yes...I have converted it to a 12V system. I do have an external resister attached to the coil for the conversion. Yes..I will get a vented gas cap. However, even if I loosen my original gas cap...(how much more vented can you get)...same problem occurs.

Gas does not drip out of the carburetor once I start it. It only occurs after I shut the engine off and try starting it again after it cranks over a few times. I do have a 700 amp battery, so cranking amps should not the problem.

Yesterday I did clean out the fuel line and fuel filter. I did not connect the fuel line back into the carburetor, but opened the fuel filter bowl valve to see if I got any flow. Gas fully flowed out of the line, so no problem with gas tank, gas filter bowl or gas line.

I'm thinking if I had an ignition problem, or a coil issue, it would have to be caused by heat. I can start the engine, then shut it off and it will not start again, so I'm thinking there's not enough time to be caused by heat. Or, once it's running it will stay running until I shut it off, so again, I don't think its heat related.

The only thing left that I can think of is something to do with the carburetor that some of the reply's mention. I'll check it over the weekend, but I'm leaning to the last reply as a root cause for the problem. I'm pretty sure my carburetor does not have a spring for the float. Don't recall having to deal with one when I replaced the parts on it from a kit, but it is worth checking it again.

Thanks for all the help and any other ideas are surely welcomed.

Get a six volt optima red-top battery. It will then have to practically slow down to idle when starting.
I put one in my 300RC and have had no starting issues hot or cold since.
Re-set the float in the carb to factory specs. Check the float for pin holes or leaks. Check the hinge pin it rides on.
Check the needle & seat if the needle has a rubber tip, replace it with a complete metal needle & matching seat.

And the problems keep mounting...LOL.

Okay...last week it appeared the battery died...I guess after all that cranking. After re-charging it the motor still won't turn over. I was wondering what is wrong now???????. Found out my starter got stuck and after I loosened it and reset it it still didn't work. Then playing with the brushes I notice one was not making contact. It was pretty worn out. Okay...no problem right? Well now I'm looking for brushes. Case/IH doesn't sell individual brushes...no...they will sell a re-built starter for $311...with trade-in of the old starter of course. I also think the solenoid is shot as well. That sweet little piece is about $30 from external link parts.

So now I'm looking at electric motor shops to see if I can get a replacement or similar brush. Even thinking about just buying a carbon graphite rod and making the part myself. As for the solenoid, I'm hoping I can find a cheaper one. I really need to test it first. I noticed that it was marked as a 6V solenoid, but when I checked the voltage across it it read 12V, so I'm thinking I fried it after all that cranking. Problems...problems...problems...life is fun!