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Carb leaking on M

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JDZ

11-06-2007 08:39:56

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The other day, I shut off my Farmall M and walked away, like I always have. A few hours later, I noticed it was leaking a steady stream of gasoline out the bottom of the carburetor. I didn't have time to look at it then, so I shut the gas off at the sediment bowl. When I got back to it a couple days later, and turned the gas back on, nothing leaked. So I started the tractor, ran it for a few minutes, and shut it off again. This time, only a few drops dripped from the carb. It was coming out of the bottom of the carb. It looked like there was a plug missing there, because I could see something that looked like brass up inside. Is it simply a plug that goes there? Why was the tractor running fine if a plug is missing from the bottom of the carb? Any help would be appreciated.

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Dave H (MI)

11-06-2007 11:06:57

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 08:39:56

I gotta tell ya, stuff happens in that fuel delivery system and the next thing you know $$$ all over the floor and a fire hazard. I was told to shut off the fuel if I am leaving it for more than 10 minutes and that is what I do....religiously.

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Nat 2

11-06-2007 09:55:36

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Re: Carb leaking on M in reply to Ed Hotaling, 11-06-2007 08:39:56

Running the tractor out of gas probably caused a bit of crud to get sucked in from the bottom of the tank or the sediment bowl.

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JDZ

11-06-2007 09:52:47

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 08:39:56

So, when I look up at the bottom of the carb, if I see a brass looking disk with a hole in the middle, that is normal?

The drain thing makes more sense to me now. I didn't realize IH carbs had that feature. I am more familiar with John Deeres and always shut the gas off on them, because the needle and seats have a tendency to leak. But this M was never shut off before I got it, so I just never did it. I will now. Another thing I didn't mention before, is that I ran the tractor out of fuel earlier in the week. I suppose that is what caused the needle to hold open or the float to stick.

Thanks for helping out an IH newbie.

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Bob M

11-06-2007 10:59:07

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 09:52:47

That brass disk with the hole in the center is the filter button retainer. You should be able to pry it out with little effort. Then stuff a piece of felt, fine steel wool, fiberglass insulation or similar into the opening and press the brass disk back in. You should be set for another 50 years or so!

Running out of gas could indeed cause the float needle to not work properly. Could be a bit of junk got brought into the caburetor from the bottom of the tank along with the last few drops of gas. Or the float dropping lower than normal in the bowl as the gas was used up may have caused it to stick, or the needle to become cocked and seat itself improperly. When that happens sometimes a couple light raps on the float bowl with the wood hammer handle will get it working right again.

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Bob M

11-06-2007 09:21:21

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 08:39:56

The opening in the bottom of the air inlet is a drain to let accumulated gas out should the carb flood.

There's supposed be a small felt filter "button" retained by a stamped sheet metal washer pressed into the opening. With the filter button is missing it will let a small amount of unfiltered air into the carburetor when the engine is running - not a big deal unless you use the tractor a lot under dusty conditions.

Note that plugging the opening solid can result in filling the air cleaner and the engine cylinders with gas should the carb float fail!!

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RustyFarmall

11-06-2007 09:20:13

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 08:39:56

That plug in the bottom is there to allow condensation a way to exit. Gasoline will also exit through this hole if the carb floods. The brass thing you saw is a filter to prevent dirt and dust from getting in. There is supposed to be a small disk, sort of like a freeze plug, to hold the brass filter in. The disk is sort of an expansion fit deal, so it is possible that it could have just fallen out although that is not likely unless someone did not install it properly. The beginning of the fuel leakage problem is most likely just a small speck of rust that somehow found its way to the needle valve in the carb, and prevented the needle from fully stopping the flow of fuel. If you could somehow get that speck of rust out of there, your problems would be over, but there really is no good way to do that without disassembly of the carb. It is highly likely that once the carb is opened up, a few more problems will be revealed, so it might be best to do a total rebuild on it, or swap it out for a rebuilt unit. If you are not comfortable attempting it yourself, there are folks who can do it for you.

Do it right the first time and you will not have to worry about it again for a very long time.

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CENTAUR

11-06-2007 10:21:14

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Re: Carb leaking on M in reply to RustyFarmall, 11-06-2007 09:20:13

The way to simply clean small pieces of dirt from ANY needle and seat is to turn off or block the fuel off and start the engine and run at 1/2 half throttle till it stops running because of a lack of fuel. Bowl is now completely empty and the needle and seat will be flushed clean when you let the fuel run again as the float drops and allows the needle to drop away from its seat in the wide open position.This procedure often has to be done even if the carburetor is NEW or REBUILT. CENTAUR

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RustyFarmall

11-06-2007 13:30:07

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Re: Carb leaking on M in reply to CENTAUR, 11-06-2007 10:21:14

That tiny little speck of rust more often than not will embed itself into the viton tip of the needle valve, and cannot be simply flushed away.

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glennster

11-06-2007 09:12:02

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Re: Carb leaking on M in reply to JDZ, 11-06-2007 08:39:56

there is a drain on the bottom of the carb for just that purpose. get in the habit of Always shutting of the gas when you stop the tractor. usually a little bit of dirt will cause the float to stick and you get a streamer!!!. at 3 dollars a gallon, its a lot cheaper to turn the fuel off.

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