Farmall only runs with choke closed

R Weld

Member
I bought a Farmall M recently that needed carb work. It starts, and will idle, but only with the choke closed. It will not idle up as high my Dads M and stalls when trying to rev up the engine. I'm thinking I need a rebuilt carb...someone told me to replace the governor as well??? Anybody have any insight? Thanks
 
Check your fuel flow at carb.If that is good check screen in carb.Don't touch governor that is not your problem.Check these first and post back.Scott
 
I cleaned the sediment bowl, put an inline filter in, blew the screen out. The screen had a few particles in it, but not much. I did all of that prior to starting it.
 
Carb rebuild sounds like a good idea. At least a good soaking in cleaner. Also check the gas tank for rust or whatever.

That fuel filter might cause more problems than it fixes on a gravity feed system.
 
Any chance the carburetor has been apart recently? Those symptoms sounds just like how they act when the venturi is installed upside down.
 
The carb was taken apart by the owner to check the floats and give it an "overall cleaning"...ensuring that the floats weren't stuck. I haven't touched the carb, other than to check the screen. I've never attempted much carb work, other than to set an idle or hook up a choke. I have rebuilt gas engines, but just never did any serious carb work. The idea of attempting a rebuild makes me a little hesitant. lol. I'd almost rather buy a rebuilt carb from external_link or some other vendor.
 
It's clearly not getting enough gas for the proper gas/air ratio.

First be sure the problem isn't too much air. Make sure there are no leaks in the manifold - rust holes, or bad gaskets, or even the carb itself. (with the engine idling - an unlit propane torch held near the suspected areas can highlight a leak)

Assuming it's all tight...

The fact that it won't idle unless it's choked means it's not getting enough gas through the carb, but IS getting enough TO the carb to idle.

It dies when you rev it, so it's possible it's not getting enough gas TO the carb for high rpm's but I'd take that as a separate problem for now.

You know there's a problem IN the carb, and fixing that may very likely solve both low and high rev problems.

Cleaning the insides of the carb is important - but not all that helpful if you don't get the very small passageways. I'm guessing you missed something when you cleaned it.

You didn't mention the mixture screws... I'm assuming you've tried adjusting them. If not, do that before doing anything else.
 
don't fear the carb!

Take this opportunity to dig into it.

Your tractor's dead anyways, you're not going to make it any worse. So it's a perfect opportunity to learn.

Carbs don't get all that much more basic than the M's.

There's very little in there to worry about.

Learn now and the knowledge will pay off more than you can imagine (the next 10 times you have trouble).

Once you do it, you'll be able to field strip it, clean it, and have it back in working order in less than half an hour, without even driving back to the barn.
 
don't mean to sound silly, but are you sure you have nice fresh gas?
i got a 300 U that ran like your. always had to dump 3-4 or more sediment bowls of fuel before she'ld rev up. Then I found a crack on the top of the gas tank from somebody brazing the filler in.
2 fingers of roofing tar on the 6 inch crack and I have no more trouble. This ethanol gas will burn when you dump it out, like kerosene; but it wont go 'POOF' like gas. Dump it out in clean can, replace with nice fresh. If that dont work, you still have the gas and out only time
 
(quoted from post at 16:23:36 08/11/14) I bought a Farmall M recently that needed carb work. It starts, and will idle, but only with the choke closed. It will not idle up as high my Dads M and stalls when trying to rev up the engine. I'm thinking I need a rebuilt carb...someone told me to replace the governor as well??? Anybody have any insight? Thanks

There is a fine mesh screen in the fuel inlet fitting on the carb. That screen is probably full of crud. The fitting is made of brass, and takes a 5/8" wrench. Remove it, clean the screen with aerosol carb cleaner and compressed air. If the screen is missing, then someone before you took it out because it was plugged up. If that has happened, you will need to take the carb apart and clean it thoroughly.
 
Is there a plastic or brass venturi in the carb? This has to go big end up, it sounds like yours is missing or upside down. Don't waste the $$$$$$ for a new carb - Let us know here -
 

The venturi is made of pot metal. It is impossible to install it upside down. It physically will not fit that way without something getting broken in the process.

Now if we were talking about a Marvel-Schebler on an 8n Ford, yes, that venturi will fit either way.
 

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