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farmall m cuts out when under a load- push clutch in and ...

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wallylucius

New User
ive got a farmall M - possibly mid 1940,s- it runs good for half hour or so then starts cutting out as if you were turning the key off and on - when i push the clutch in it will sit and idle just fine at whatever RPM,s im running- let the clutch out and itll start cutting out again- if i let it sit a few hours it runs fine for half hour or so then starts cutting out again- what the heck? anyone have any experience with this? i use it for food plots for wild life so only use it in suspring n summer and early fall-it sits in a shed all winter- any help is appreciated
 
Sounds like crud in the fuel supply components. Start with the bowl at the tank and work your way to the carb. Remove and clean each one. Also, there is a screen in the inlet on the carb. Make sure that is clean as well.

Also, when was the last time this was tuned up. Plugs, wires, points, condenser, etc.
 
Open the main jet adjustment screw near the bottom of the carburetor to see if this fixes the problem. Hal
 
If it runs fine for half an hour, it's probably not the carb... Though I say probably hesitantly as it very well could be.

Quickest test for the carb is to choke it a little while it's having difficulty. Half way should be enough - but play around with it. If it improves, then it probably IS the carb... (not getting enough gas through the carb - needs cleaning)

But if it doesn't help - I'd check the coil. That's what I'm guessing the problem is.

I've read janicholson's recommendations here of feeling the coil to see if it's hot. They all get hot, but according to him, almost too hot to touch. I've never felt one like that, but I trust his word.

You can also pull a plug wire while it's running and check the spart against the engine. Look for a good long blue spark. If it's weak, the coil's probably bad.

Let us know what you find.
 
sorry - meant to say when checking the spark - check it once before the problem as a reference - then check it while you're having the problem to see if there's a difference.
 
I did try pulling the choke and seemed to get some what better- kinda boggy as you would imagine when pulling the choke but better- didnt cut out- so was wondering bout that myself- i did put a new coil onit also with no improvement
 
Check to make sure the points gap is right. Had one act the exact same way once, rub block had wore out prematurely.(Cheap points Dad put in to get through a bind.) Would run fine for a few minutes, then start cutting out.
 
Take the Fuel cap off when it does it ifit perks right up the vent is plugged up. Also check the distributor shaft for bushing wear. The cam must not move more than .001" side to side (not in and out) in any direction, up down in out etc. Gap is .020"
Jim
 
I agree with Janicholson on the fuel cap. My A did the exact same thing you discribe and it turned out to be a clogged vent in the fuel cap.
 
Yea,if its not the cap vent,it might be the coil or ballast resistor???

My Super M was doing this a few weeks ago.When my ballast resistor was getting hot,it was "cutting out"the ignition.(I ohm ed it right when it quit.)I have seen MANY coils "break down" when they get warm,as well.You let them cool off and they will start working again,then drop back out when warmed up again.
 
(quoted from post at 23:11:13 09/28/11) ive got a farmall M - possibly mid 1940,s- it runs good for half hour or so then starts cutting out as if you were turning the key off and on - when i push the clutch in it will sit and idle just fine at whatever RPM,s im running- let the clutch out and itll start cutting out again- if i let it sit a few hours it runs fine for half hour or so then starts cutting out again- what the heck? anyone have any experience with this? i use it for food plots for wild life so only use it in suspring n summer and early fall-it sits in a shed all winter- any help is appreciated
Click to expand...

Pull the valve cover and check the clearance gap on the valves. I think you find the gap is way too narrow, and when the engine gets warmed up, the gap goes away altogether, and then the valves can no longer close completely, which will result in erratic running and loss of power. The book calls for 0.017" clearance gap with the engine hot, but if you set 'em at 0.020" cold, you will be in the ball park.
 
I would do as others have said - try the gas cap thing obviously - and definitely make sure the valves are adjusted... but it still sounds ignition related to me.

Just to be clear, it runs fine for half an hour first? Is that true? Runs strong under load?

If the above doesn't fix it - I'd definitely check the spark before and during the problem.

And I'd focus a little more on the ignition - clean the points, etc. Did you change the condednsor?

Sorry if you've already answer some of these questions - I have a very short attention span!
 
i did replace the coil and its still doing it- not sure where the ballast resistor is or what it does- but im goingnorth to the cabin again this weekend and will check all the things you all have told me about startingn with the fuel cap which ill check first - or last , whatever-will check fuel lines for being plugged and inlet screen on fuel line which is just b4 the carb i guess- didnt know that was there either- really appreciate all the advice-its sure a pain going to the cabin 133 miles and not having the tractor run so i dont get anything done- any other suggestions are certainly appreciated
 
MY suggestion to you is to put an electronic ignition on your m. you eliminate fouling plugs and many hard startups. also convert it to 12 volt alternator style system if this has not been done yet. it isnt very expensive and in my opinion is the best thing you can do for an old gasser like that.
tony
 
its been converted to 12 volt and alternator but not electronic ignition- how hard is the ignition to install and whats the cost?
 
Wally before you go crazy changing things out, make a short list of what has been suggested around valve lash, fuel supply components, etc. Make sure what you already have is working and clean.

Then you can start replacing things. These old girls are actually pretty forgiving if they have air, fuel, and good spark.
 
If it has a ballast resistor,it would be installed in the + power wire running to the coil.Somewhere between the ignition switch and the coil hotwire.(Should be a white "block"looking thing about 3 inches long.)
 
thats what i was thinking of doing is making alist- the fuel cap and carb inlet screen sounds like a great place to start and mabe file the points a bit and readjust- wish i had a pic of a carb so id know which needles are which so i could adjust those as its possible someone stopped by and messed with those also
 
Did you try opening this screw? Hal
a50402.jpg
 
i did change the plugs and new wires also- i will have to change the condenser i guess and will drain out the carb and see if that works- also clean the scren on the carb if its got one and do the gas cap thing also- will see how its going- as im going to the cabin today- will let you all know how it goes
 
That screw is not a drain!!! it is an adjustment for full throttle load control fuel enrichment. Turning it outward "Lefty Loosy" 1/2 turn at a time will richen the mix of fuel to air at high power/load. Try it. Jim
 
seriously? its not a drain? well, i turned it out and it did drain the carburetor- the holes in it were packed with dirt so i cleandit all out- sooooo--- how many turns out should i start with when trying to adjust it? it was stuck tight so i turned it in tight- should i start by tightening it and then backing it out a half turn? what do the other two screws- or needles? do and which is which? one has to be the idle setting i assume
 
actually after looking at that carburetor pic and the pic i took of mine- its a bit different type carburetor- i got a couple numbers off the side of the carb body-0 they are6513D as far as i can see after cleaning all the gunk off it- do those numbers mean nything to anyone?
I also found that my fuel line from the sediment bowl to the carb( rubber fuel line) has a weak spot and is seeping a very minor bit of gas out so im going to replace it also and ill be replacing the ballast resistor also as ive located one for it
 
I also removed the sediment bowl- i as draining the carb and noticed a lot of jelly like and also flaky dirt in it- i also cleaned the fuel filter going into the carb- now have to get the fuel line replaced b4 i can test drive it- another weekend shot and more money-- does anyone think i should just pull the steering wheel and drive a new tractor under it????
 
That screw is likely the whole issue. It will drain the carb because it is in gasoline. The screw adjusts the fine tuning of the power jet. If it is shut it will not have full power and run very badly. The initial setting is 3 to 4 complete turns out.
From there adjust in until it starts to act like it did, then turn it out one turn. in heavy real work, it should be turned out till the muffler gasses are just a little black, then turned in till they clear up. Rubber hose is not as good as fuel injection hose with reinforcement for pressure. It has no pressure, but the fuel is under gravity feed and if it breaks or leaks seriously it will burn the tractor. The best is the original Steel line. Best of luck, it will be great. Jim
 
I experienced those exact same symptoms you are describing a year ago. Very frustrating. Cleaned carb up real good, put carb kit in her, and symptoms disappeared.
 
thanx for all the help uve given me- and to all the othersalso- well i will have to give that a try after i get the fuel line bought and installed- probly going back up to the cabin next weekend to have another talk with the tractor- and a lil bow hunting if all goes well- ill keep you posted on how it turns out
 
did it bog down like f;looding or not enuff gas or did it just plain cut out- like someone turning on and off the switch real fast?thats what mines doing- its as if the spark to the plugs is being shut off and on every couple seconds
 
They are about 5 bucks.
I didnt know if the tractor was a 12 volt system or not?

WARNING: they come in different levels of resistance.We need to know if your coil is 6 or a 12 volt coil? If you DO NOT know which coil you have,take an ohm meter,touch it to the + and - on the coil with NO wires hooked to it,and hold it them there for a few seconds.

If the reading is around 1.2 ohms it would be considerd a 6 volt.If it is about 1.5 ohmns,it would be considered a 12 volt.A good resistor is NAPA part # ICR13 is aproximately 1.8 ohms and should work out to reduce either of those coils to the reccomended 2.7 to 3.3 TOTAL ohm requirement/resistance to keep from burning up your new points.(this comes from the discussion forum on here"recomendations for 12 volt conversion")
 
it is a 12 volt system so im guessing the 12 volt resistor- there is a guy in Henderso who specializes in old tractors and i will probably run down there to get one-someone also seems to have "borrowed" my oil filler cap so will need another
 
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