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Farmall M problems still

T

tripleccattleco

New User
I posted last week about some problems I was having with
my M.The tractor would idle fine but when you started pulling
the throttle back it would die. The tractor would not rev up at
all. Several of you said the main jet was possibly dirty. I
soaked the carb in carb cleaner overnight and blew
everything out with the air compressor. I put it back on, this
time, it will idle just like before, with the choke closed. I
opened the choke very slightly and it reved up to about half
throttle, it will still not rev up with the throttle lever, if I open
the choke all the way it idles back down and runs a little
rougher. I did check the fuel level in the carb and it is at the
correct level. I would appreciate any advice I can get! I can
also be reached at 573-718-0261. I'm getting very frustrated
with this, the local guys all have newer tractors and aren't
much help. Thanks! Chris
 
I wasn't clear on one thing - is it running better while choked? or not?

If it does run better while choked, you're most likely not getting enough gas through the carb, into the engine.

Did you take the carb apart, or just soak it?

You need to pull it apart and clean out the passageways with a thin wire.
 
You may also have an ignition problem. Does is run any different if you add choke while speeding it up, if not it could be timing or spark?
 
What does this mean? You took the top and bottom apart and that's all? You need to take it ALL apart, every jet, screw and plate.
Buy the complete kit. It comes with instructions.
If you don't feel you can do it find someone who can. RustyFarmall on this forum is the master with M carbs.
 
There are few things harder to diagnose on line than what appear to be fuel system issues. I need to be certain of one issue. In your post above you indicate that it idles with the choke closed. In normal terms, closing the choke is a starting procedure that actually blocks the air intake richening the mix radically. If it runs after starting with the choke closed (rod pulled out toward the driver), there is something very wrong, the tractor should idle and run with the choke open. Rod pushed in!!
Help us on that issue first, as all answers depend on clarification. Jim
 
If it were me, I'd take the carb apart again, go through any passageways with a wire to clean them out completely.

Been a while since I've worked on a carb for an M, so can't tell you exactly what to look for. Maybe somebody else here can.

You also want to be sure you don't have a vacuum leak anywhere, bad carb gasket, manifold gasket, that kind of thing.

Make sure you've got a good strong spark with a spare plug too, but it really sounds like a carb problem to me.

If it runs good choked, that's a strong sign that it's getting plenty of gas into the carb, but not enough out of the carb to the engine.
 
It will run with the choke open but you have to leave the choke closed for 15 minutes or so before doing so or it will die as soon as you open the choke fully.
 
Again this is not clear (I am not being obnoxious), the choke is closed when the rod is out it should only run for 5 seconds with it closed (out), then start smoking black and making gasping sounds toward stopping.
If this is the way it is operating, Choke pulled out for 15 minutes, there may be a radical manifold leak into the engine where the intake runners are held to the head, or at the Carb to manifold gasket.
A spray of carb cleaner, or WD40, or an unlit propane torch with propane coming out moved around the manifold and carb when it idles will cause it to perk up instantly when the extra fuel is sucked into the leak. If there is a crack in the exhaust manifold internal to the intake manifold (not on the outside) these symptoms can occur.
If your description of the choke being pulled out and it running is correct, the fuel may not be getting to the carb through the strainer in the fitting on the carb inlet. (just one more easy check) Jim
 
Oh, and before doing anything, be sure the mixture screws are at least in the right ballpark.

again, it's been a while for me, so I'm sure somebody here can tell you where they should be -

I think the top one should be turned in all the way, then out 1 full turn?

The bottom in all the way, and out three turns?

Then adjust from there.

Don't take my word on # of turns out - wait for somebody who knows.
 
I understand that your not being obnoxious. That's the only way I can keep it running after its started (choke closed), after it has warmed up, I guess you could say,then you can open the choke. I will try that also, i'm willing to try anything.
 
Check your fuel supply as well at the tank,You COULD have a restriction a t the sediment bowl or tank,(happened to me MORE than once untill I cleaned the tank out !!!!) Pull the lie loose at the carb,open the petcock,and see if it flows freely.)But yet,could still be a carb issue,as well?Hard to tell without being right there with ya.
 
Forgot to mention,

Also check inlet screen on carb fitting when you have fuel line loose at carb.This is a common issue,as well.
 
I'm wondering here if the carb hasn't been apart before you got the tractor?? If the person who worked on it previously hadn't put the venturi air horn or something similar back in when working on it, that could cause all sorts of problems. The best thing at this point would be putting a known good carb on & see if it performed correctly. If the same symptoms were evident, it would have to be problems with holes in the manifold or intake gaskets not sealing, or------. Not the carb.
 
That only works if you have another M with a known-working carb on it sitting around... Or, I suppose you can buy a rebuilt carburetor but that's a big chunk of change, and they usually get banged around during shipment and need to be taken apart and fixed before you can use them.

The easiest thing now is to try the propane trick and look for a manifold leak. You should not notice a change in how the tractor runs as you run the unlit torch around the manifold. Don't worry, you will NOT "blow up." The engine fan blows the excess propane away before it can build up to explosive levels.

Next, disconnect the fuel line from the carburetor and check for fuel flow. It should run a full strong stream of gasoline out of the fuel line.

If both those tests pass, you need to take the carburetor apart, do a REAL cleaning, and install a carburetor kit in it.
 
You can check for manifold leaks by spraying WD-40, carb cleaner, propane, or something like that along the gasket area. Plain motor oil will work, as it is thick enough to partially plug any leaks. Even if the material is non-flammable it will change the air fuel mix as it is pulled into the crack. DO NOT use ether.
 
Thanks everyone, for all of your help, I will try all of the ideas you have brought to my attention. If you happen to have any more ideas don’t hesitate to tell me! I really appreciate the help! Thanks Chris!
 
How close to the SD/ND/MN border? Could maybe if not to far come and take the carb down and help you with it if. I'm not too far from Fergus Falls Mn.

Rick
 
just for giggles, when you had the carburetor apart, was the venturi still in there? it is a sleeve looking deal that fits in the center of the lower fuel bowl and slides up inside the upper body of the carb. if you go to the case ih website and look up parts for the m, it is part number 42 on the exploded view. it is possible it fell out when you had the carb apart and you didnt notice it.
 
couple other thoughts, check for a good blue spark at the plugs, if you have a spare spark plug, just hook it to one of the plug wires and lay it on the engine, start tractor and observe spark. next, pull the distributor cap and wiggle the rotor side to side to check the bearings for excessive wear. if all that checks out, i'd look at the fuel delivery to eliminate that. on the bottom of the fuel bowl is a drain plug for the carb. pull that out, go to the hardware store and get a brass barb fitting that you can screw in to the carb bowl and connect some clear fuel line to. about a foot of fuel line will be good. put the fitting in the bowl, hook up the clear fuel line and route the other end vertically above the carb. it will act as a "sight glass" to show you the fuel level in the bowl. turn the fuel on and see where the level goes along the body of the carb. make a note of it. next, start the tractor and let it run, watch the level and see if it drops. throttle the tractor up and down and see what happens. the level should stay pretty much the same. if it drops, you know you have a problem between the needle and seat in the carb and the fuel tank. if it holds the correct level, the problem is between the fuel bowl and combustion chamber.
 
Hold your hand over the throat of the carburetor while a helper cranks over the engine using the starter. If there's weak suction it means you have low intake manifold vacuum. Could be just a gasket leaking. Worn sleeves and valves not seating will cause it too. Hal
 
Ok you should have a drain on the carb bowl. May be a wing nut looking thing ot a plug that screws out. Take a clean container, open the drain and watch the fuel flow. It should be a steady stream and should run that way all the time. Let it run for a minute or 2 to be sure. If it's not a steady stream then you have a blockage BEFORE OR AT the needle and seat. If you have good flow then something is plugged in the primary circut of the carb.

Rick
 
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