51 "M" hard start

mailman1

New User
I have a 51 gas "M" that has been getting harder to start regardless if it is hot or cold outside. I have it wired to 12Volt so it will spin it over aa good clip but doesn't seem to be getting gas up to the cly. If I prime the cly. with gas then when I turn it over it will start and run like there is no problem. I have had the exhaust manifold off a while back and noticed there was some pitting on the manifold ports, and was wondering if that could cause enough of a vacuum leak not to be able to draw gas up into the clys. Any help and or advise is welcome. Thanks
 
Do some simple trouble shooting.
#1 make sure you have a good blue/white spark that will jump a 1/4 inch gap at the center wire of the distributor cap and at all 4 plugs.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fill a pint jar in less then 3 minutes.
#3 when was the last time you serviced the air cleaner and dumped the mud and water out and fill with new oil?
#4 pull the air intake tube off the carb and hold you hand over the air intake of the carb and make sure you have a good suction there and also your hand gets gas on it while spinning it over. It may even try to start when you do that
 
Yep they fill up with caked grease on the inside of the upright stack, got to put a washer on the end of a rod with the bottom oil cup off, and push it out, but that's not the problem with it not starting good.
 
It sounds like either a vacuum leak or the
choke isn't closing fully or both. Like
what was suggested holding your hand over
the intake side of the carb while you crank
it over is a good place to start.

Another possibility could be burned points
if the 12 volt conversion wasn't done
right.
 

I took the bottom drain plug out and got no gas but the plug had a hole drilled through the center of it. Took the fuel line loose at the carb. and had plenty of gas although a year ago I replaced the sediment bulb as the original one was gone, just a fitting into the tank, so I took it loose to clean the crud out and replaced it and when I would tighten the bottom nut on the bowl tight it would not let the gas fill the bowl, I had to loosen the nut some in order to get the gas to flow. Cleaned the oil bath and replaced with new oil and will try hand over the carb air orifice in the morning while I crank it.
 
That plug with hole is not the carb drain plug. It is there for gas to drip out if carb is flooded. There is a small pipe plug on front bottom that drains carb.
The sediment will fill when you start to crank engine.
a251871.jpg
 
You need to take the fitting out where the fuel line goes in and clean the crud out of there. There should be a filter, but it could have been removed somewhere in it past. If that's OK, then either the float is stuck, or theres crud in the needle and seat.
 
If you did in fact take the drain plug out and had no gas then you have a carb problem and have either a sticking needle valve or float but when you prime it the vibration of the engine shakes things loos so it will then run.
 
Of all the M's , super M's, 400 and 450 in our area I have never seen a drain like that on carb. and can't find any listing for one. The only carb that used that drain was on the starting carb of MD,400D, and 450D.
 
That part number was used on a (046) carbureted carburetor for gasoline,distilate, kerosene engines. The carburetors for straight gasoline didn't use that valve. I grew up around the gasoline m's,super m ,400 and 450 in the 50's and own a 51 M and 58 450 and none of them had a drain cock like that they all used a pipe plug.
 
Thats true, but it could have been added to the others as well, maybe a regional thing. Most of the tractors around here were kerosene burners, and ours did during the gas shortage during the 70s, and most of them are still running.
 
(quoted from post at 19:08:42 12/28/17) He has this type of drain plug. It has a hole down the middle, and two small holes on the bottom of the threads.
Here.

That style came on the distillate/kerosene tractors. It allowed the carburetor to be drained of the distillate, so that gasoline could be introduced for purposes of starting. A cold tractor will not start on distillate.
 


Your right about the drain plug, my dad had a 42 tractor fuel M and it had the drain cock on it. Now I went to see about trying to start my M this morning and even though I had the charger on it last night it would barely turn over. I took the battery out and saw it was over 5 years old so that could be part of the problem but when I put my hand over the carb. when I did crank it felt like it wanted to suck my hand into the carb so I think that would mean that there is suction there, correct me if I'm wrong. Off to get a new battery.
 
#1 a weak battery can well be most if not all of your problem since a weak battery cannot you have poor spark.
#2 you say you had good suction at the carb but did your hand also get gas on it??
 

I put the new battery in the tractor, then I checked the other plug not the bottom one on the carb. and there was plenty of gas coming out when I took it loose. Tryed to start it but no go. I went ahead and primed the cly.and tryed again and then it fired once but didnt start but I held my hand over the carb. and got gas on my hand when I cranked it. Will give it another go in the morning after
I replace the hoses on the air pipe from the oil bath.
 
Carburetor diagram. Might help. Shows drain cock for kerosene motors. Farmall AM carburetor is the same as Farmall M.
SadFarmall
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I replaced the hoses from the carb. to the oil bath then primed 2 cyls. ande tryed to start it and it fired once so I primed all 4 and tryed again and about three revolutions and it fired right off and kept running. I backed it into the shop where I have heat and can work on it inside. It's supposed to get down to -25 below tommorro night. Everything seems to run fine it just won't start when it sits over several days and seems like it can't get gas to the cyls.
 
Probably not your problem, just giving a thought. I had a Ford flat 6 that would not start using the starter. You could pull it the length of the truck
and it would fire right off. Bored worn out cylinders, installed new Pistons/rings, ground valves,seats,and never had anymore problems. Pitted
valve seats can cause this. What's your compression readings?
 

I had put new pistons and sleeves along with having the head rebuilt prior to the harder starting so I don't think that's the problem, but this morning it was -15 below and the tractor was in the shop plugged in and the charger on and it would turn it over 100 mph but not a pop. There was gas coming out of the overflow plug on the bottom so I knew it was getting gas to the carb. I then gave it a small shot of starting fluid to the air breather and about 2 rpm it fired right off and kept running which tells me that for some reason it doesn't get gas to the cyls. when it sits for a period of time.
 
Pull the air cleaner tube off and hold your hand over the air intake while cranking it to start. You should get a real good suction when you do and it may even try to start. If the suction is poor then you have a compression problem or a leak in the manifold area so it is loosing vacuum which is needed to pull gas into the cylinders
 
When I put my hand over the intake of the carb it feels like it wants to pull my hand in and I get a splattering of gas on it so I know it seems to be plenty of suction :?:
 
In that case then it is just the fact it is so cold out. Yesterday I started up one of my tractor and to get it to run U had to hold my hand over the air intake and it finally tried to start. Had to do that number of times before it did start and even then it died a couple time and I had to do the hand trick again
 
Well over the last few days I have been working on seeing if I can get the M to start easier and I had some success so I left it in the shop without heat and tried it this morning and it wouldn't start. I took the air breather pipe off to see where the choke flap was positioned and when I moved the choke lever the flap stayed in the same position, come to find out the choke cam that is attached to the choke shaft spins on the shaft so it will not choke the engine when you pull on the lever. I tried to center punch the cam and the shaft but that doesn't work and I have thought about spot welding the cam and the shaft but would have to take the carb. off just wondering if I can buy the choke shaft and cam by it's self or would I have to buy the whole kit. At least I found out why I kept having a hard time trying to start it.
 

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