Stumped with a '48 M problem

[P and R Pete]

Trying to help my father-in-law with his ’48 Farmall M.
Had been running fine or so he said, until yesterday when in trying to start it, it was a long time catching, and then ran rough, and only at idle, and it will stumble and try to die if the throttle is boosted. Even at idle, it would run for awhile, and then die as though the float bowl had run out of gas.
Some odd things, though. At times, when trying to start it, many drops of gas, and sometimes a stream of gas, would flow out of the drain hole at the bottom of the carb, as though it were getting flooded, and always there is gas flow when the drain tap is opened. We split the carb to check the float, and it is OK. We replaced the float pin and the piece that contains the seat, as the old pin was intermittently sticking. The new one does not stick at all. I wanted to spray the jets with carb cleaner, but the slotted-plug in-line with the main jet, though extremely stiff, would not back out when turned, as though it’s threads had been stripped, so I never took that out, and thus couldn’t blow out the jets from the bottom, (but maybe I’m wrong about the purpose of that plug). I did remove the main jet from above, and only that jet, and we sprayed all three jets with carb-cleaner and then compressed air, and all were open, though I can’t feel assured that there isn’t some piece of crud still floating around in there.
But I can’t help but wonder if the thing isn’t getting TOO much gas. There’s quite a bit of smoke coming out the pipe at start-up. And this odd symptom,- when it is running/stumbling, the three inches of intake manifold above the carb gets extremely cold, with moisture condensation running down that and onto the carb.
He may have other problems. The plugs were damp and black, and the inside of the cylinders looked damp, though I couldn’t tell if from gas or oil. Once we get it running, I’ll do a compression test. He’s only had this thing since Spring, and this is the first sign of trouble.
Anyone have any thoughts? I’m stumped.

 

[CNKS]

You will get a bunch of answers. My standard answer to questions such as yours is to disassemble the carb, and put the whole thing into true carb cleaner and let it set over night. Blow it out with compressed air and although you can't do this with all passages, when you blow air in it should come out somewhere. I never do anything to the jets, they might break anyway. Put in a new kit, preferably IH. Don't choke the tractor for more than a couple of revs when starting. If it does not start, gas will come out of the hole at the bottom for every IH gas engine. Be sure the float is at the correct height and that the needle does not catch in the seat. I think the starting numbers are 3 turns out for the main jet and 1.5 of so for the idle. Unless you have an electrical problem it will start. If you flood it, you have to wait a while. I think it is impossible to get too much gas unless you have to crank it a long time to get it to start--that happens very easily. In that case, yes it gets in the cylinders.

 

[Janicholson]

It might be Carb icing if the relative humidity is near 80 to 90% it will do that. The ice builds up on the discharge nozzle and venturi causing self choking to the carb.
Warm air or a cardboard over the side of the engine might allow the heat from the radiator to warm the carb. Jim

 

[mkirsch]

The tractor will behave the same way if it is getting way too much gas, or way too little. It will stumble and eventually stall.

The fact that the tractor was blowing (black?) smoke when it did run, and gas was running out of the carburetor indicates that it is getting too much fuel.

A float/needle/seat problem would cause the gas to run out.
Choking the carburetor too long would cause gas to run out.

The needle/seat may not be sealing up, and needs to be replaced. The float may be sticking, and needs to be adjusted. It can sometimes be difficult and frustrating to identify a sticking float because you can't see how the float interacts with the bowl, and you can't see it catching on the side. The float has to be aligned PERFECT or it will hang up on the side of the bowl and drive you nuts.

The amount of choke you need depends on the tractor. Some need none at all. Some need just a quick blip. Some need the choke set and left there until the tractor runs for 1-2 minutes. You need to get the feel for what the tractor wants/needs. Start with no choke at all and work your way up, instead of starting with lots of choke and wondering why the gas pours out and the tractor runs like garbage.