Farmall M Carb Troubles

[Chuck McDonald]

Good afternoon,

I have been working on a M Style Carburetor for a friend and am having some issues. The local CIH dealer supposedly rebuilt it, but I ended up putting a new float in it after they were done.....not impressed.

The original issue prior to rebuild (really just replace a few parts) was the needle would not seat and gas would just run out as you would expect. Tractor ran well, but just that issue.

After returning from IH, carb does not pour out gas when not operating, but when we try to start it, it is pushing way too much gas flooding out the motor. After 5-10 seconds of cranking with throttle at idle and choke not engaged, when you let off the starter, raw gas comes out the air intake for the carb.

I have replaced float, with new, known good float.

Also have screwed load jet as low as I dare.

Any ideas on where to start? Fuel level too high in carb?

Thanks and I apologize in advance if this is basic stuff....just has me stumped.

Chuck

 

[Charlie M]

The only way to get too much gas in the motor is to have too much sucked up by the motor and not start. That means either jets are too open, too much choke or gas is flooding over into the air intake. You said it doesn't leak gas any more then it isn't leaking as into the air intake. Maybe with a rebuilt carb you are choking it too much. If its warm where you are a M doesn't need much if any choke to start. Does the engine fire as maybe you have an ignition problem now.

 

[glennster]

here is something to check.. one of my m's ran awful rich. adjusting the main jet made no difference. finally took the carb apart and gave it a good look see. turns out at some point in the past, someone replaced the main load needle from something else. it was too short. turned all the way it, it was about 1/4 inch or so from contacting the seat. ordered a new one from your friendly case i-h dealer. kinda spendy, about 30 dollars or so, but it cured the problem.

 

[gab]

You say cranking at idle. My two tractors start right now cold but I always set the throttle at about a third, don't think they'd start good with the throttle closed.

 

[John M]

Did you set the float when you replaced it, or did you just stick it in there? Load screw wouldn't matter, except at high idle, minimum one turn out and max of 5 out. The idle mixture will cause it to run rich at idle, which you will have to adjust when its running. Also, those floats are known to hang up on the sides of the bowl, due to a worn pin, so I assume you changed that? I agree also you need to open the throttle 1.3 to 1/2 open.

 

[Ron in Nebr]

My 450 would do that too- crank 5-10 seconds, then dump gas when I quit cranking. What actually fixed it on mine was new plugs and wires. Now it starts on the first revolution, no where near 5 seconds of cranking required.

 

[Chuck McDonald]

(quoted from post at 22:33:33 01/31/17) Did you set the float when you replaced it, or did you just stick it in there? Load screw wouldn't matter, except at high idle, minimum one turn out and max of 5 out. The idle mixture will cause it to run rich at idle, which you will have to adjust when its running. Also, those floats are known to hang up on the sides of the bowl, due to a worn pin, so I assume you changed that? I agree also you need to open the throttle 1.3 to 1/2 open.

Thanks for all the replies so far.

I have had this carb on a known, well running (Read ignition is fine) tractor as I have been trying to determine its issue. We are for sure dealing with a carb issue.

The float pin looked new as I believe that IH replaced it when they were in there, but must have had a cheap kit that did not include a new float.

I have tried starting it with throttle in multiple positions. No difference, gas stream comes out of intake.

[b:5076ec7419]How high should the gas be in the carb bowl? I did not check that and feel thats where I am dorked up.[/b:5076ec7419]

Thanks!

Chuck

 

[J. David W]

From the top of the carb where it is split without the gasket it should be 1 5/32" to the top of the float/s. This is critical.

If IH rebuilt it and if they put a new needle valve in the problem could also be that they used the new needle valve that has the rubber tip and if they did not push it in to seat, the float will be higher letting more fuel in.

 

[J. David W]

I didn't ask but that dimension is for a Zenith carburetor.

 

[D Slater]

With throttle body manifold side down both sides of float should be 1-5/16 from gasket surface to top of float arms at the ends. That would be lowest part of float if installed on tractor. Can't remember for sure but think the 1-5/16 measurement is plus or minus 1/64 or 1/32. After putting carburetor back together make sure float doesn't drag on sides of bowl. Should hear float move free when turning carburetor upside down and back. Or use a spray can plastic tube through drain hole to move float up and down checking for drag. After installing a clear plastic tube with fitting and end raised above fuel level can be used to check fuel level in bowl. You can pretty well tell if needle and seat holds by turning fuel on with engine stopped for a time. If it doesn't start dripping fuel then the problem if in carburetor is somewhere else. Did they put a idle jet back in? Really unless the plugs are to wet or to fowled to fire and other ignition parts good the tractor should start right up at first, then start putting out black smoke and maybe die if to rich. No start condition after cranking results in some fuel drawn up falling back to carburetor throat and out drain or intake pipe.

 

[riverbend]

I had an odd problem with the choke on my H once. The outside lever was not tight on the shaft. I had to braze it in the correct position. it still works fine.

Having said that, most of my 'carb' problems are ignition related.

Greg

 

[Chuck McDonald]

(quoted from post at 00:14:04 02/01/17) From the top of the carb where it is split without the gasket it should be 1 5/32" to the top of the float/s. This is critical.

If IH rebuilt it and if they put a new needle valve in the problem could also be that [b:8291cf42f7]they used the new needle valve that has the rubber tip and if they did not push it in to seat, the float will be higher letting more fuel in.[/b:8291cf42f7]

Right there is the problem I think.....it is the new, rubber tipped type.....level of fuel running too high is my guess now for sure....

Will try some stuff tomorrow and let you guys know the results!

Thanks again for all the help....

Chuck

 

[rustyfarmall]

(quoted from post at 19:00:55 01/31/17)

(quoted from post at 00:14:04 02/01/17) From the top of the carb where it is split without the gasket it should be 1 5/32" to the top of the float/s. This is critical.

If IH rebuilt it and if they put a new needle valve in the problem could also be that [b:a139f46abe]they used the new needle valve that has the rubber tip and if they did not push it in to seat, the float will be higher letting more fuel in.[/b:a139f46abe]

Right there is the problem I think.....it is the new, rubber tipped type.....level of fuel running too high is my guess now for sure....

Will try some stuff tomorrow and let you guys know the results!

Thanks again for all the help....

Chuck

The rubber tipped float valve has nothing to do with it, and besides that, the rubber tipped is the only one available. I've rebuilt MANY Farmall H and M carbs using that rubber tipped valve. Never had an issue with any of them.

 

[gab]

You can replace the carb. drain plug with a barbed fitting and a clear hose fastened higher than the carb. Think it's supposed to be 5/8 of an inch below the gasket. Might of been Pete23 that posted that a year or two ago.

 

[rustyfarmall]

Specified float height is not just a suggestion.

 

[J. David W]

It does if it was not seated to take the shape of the seat. If not the float will be too high.
I bought a kit and did not use this because of the rubber, went back and used the old all metal one and made sure the float was set at the correct height from the Service Manual, 1 5/32".

 

[rustyfarmall]

(quoted from post at 15:43:54 02/01/17) It does if it was not seated to take the shape of the seat. If not the float will be too high.
I bought a kit and did not use this because of the rubber, went back and used the old all metal one and made sure the float was set at the correct height from the Service Manual, 1 5/32".

If you took the time to look at the old, all steel needle valve, you would notice that it most likely has a prominent groove worn into it. That groove is where it will begin leaking. Rubber tipped valves do not wear out, they just get dirty.

Seating the needle into the seat is a myth and should never be attempted. If the needle doesn't fit, hammering on it will not fix it.

 

[J. David W]

I've owned this tractor since 2002 and haven't done much to it as to maintenance. I finally put lights on it and wanted to look at the carburetor and starter. It was running fine, but I took the carb off and opened it up per the Service Manual, I replaced the metering valve and seat even though mine were fine. I put some of the parts and put the new seat in and then put the new valve in, and when putting the float on saw that the float was way too high, way above what the specifications stated. I was not going to bend the leaf of the float that much so I just used my old valve and seat. The measurements were right at their specifications.
I don't know how you can just put the metering valve in as the rubber tip will hold the valve too high, I had read that you have to push it in to form the seal (nobody said anything about a hammer). My metering valve did not have a ring and I don't know how you would get a groove in one unless you were using dirty gas all the time. You are talking steel valve against a brass seat.

My problem on leakage was that I ordered the wrong gasket kit as the supplier did not mention carburetor models just that it would fit lettered models. WRONG, you need to know you carburetor number. Mine was on a round disc.

 

[slim51015]

Sounds like water in the gas or bad gas. I own a 300 and had this problem alot. Drain a couple quarts from carburetor drain then try it.

 

[D Slater]

M carburetor is a IH model E12 and float setting is 1-5/16, that should leave fuel level 9/16 below throttle body gasket surface if checking with a clear hose from carburetor drain plug. Don't know what manual you are looking at.

 

[J. David W]

(quoted from post at 08:26:37 02/03/17) M carburetor is a IH model E12 and float setting is 1-5/16, that should leave fuel level 9/16 below throttle body gasket surface if checking with a clear hose from carburetor drain plug. Don't know what manual you are looking at.

Sorry about that, I was thinking of the dimensions for the smaller tractors, A, B, BN.