Farmall M, Super M, 400, 450 & 560 Tractors, 1939-1963
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I can not for the life of me get this thing to run or even hint that its trying to fire. It ran just over a month ago and yesterday when I tried to start it it would try to fire a few times then die and now wont even try. Here is what I have done:
drained gas tank, cleaned sediment bowl and put fresh gas in.
took carburetor off and cleaned it out
pulled plugs and checked gap electrode etc.
double checked wiring to be proper sequence.
checked rotor and dist. cap seems ok
checked for fuel delivery to carb...YES
checked for spark at plugs.....YES
Has suction at air intake on carb when cranking
I have always had a carb problem on this tractor ( leaks gas from carb pretty bad) so I would just shut the valve off when not in use. but it has always fired right up.
I am getting a crb kit and going to go through it
Any thoughts as to what my problem could be here??
Any thoughts as to where to go from here?
dripping carb sounds like flooding. This a 6volt system? Is is cold out? Do you have any idea what the condition of the valves are? I know cold weather and crappy valves and lash/gap can make it nearly impossible to start.
An easy thing to start with, and even if it not the problem still good to do anyway, is make sure the valves are gapped correctly. They should be 0.017 inches (hot). So since you'll have to adjust them cold I'd go with 0.019.
Also, do a compression test.
I believe you should have about 125-130 psi in each cylinder. Poor compression will indicate a bad seal with the valves which will make starting hard. My Super A had awful valves but ran in warmer (32F+) weather. When it got cold it wouldn't start. That could explain why it ran before and now it doesn't, if in fact it has gotten cold for you.
It is quite warm upper 50's yesterday. When it ran a month ago it was probably low 20's at night and 30's in the day. What exactly is the process for adjusting the valves?
Also, yes it is 6volt system. I did try taking the plugs out, squirt some starter fluid in, put the plugs back in and tried to start which it did fire for about 3 seconds. but I could not duplicate that process again.
Adjusting valves is easy.
Get a feeler gauge. Take the valve cover off. Bring piston 1 to top dead center on the Compression stroke. Take the sparkplug out when you do this and stick your finger over the hole, you'll feel the air move past your finger. Basically both valves are closed and the air that would normally be compressed is moving out the open plug hole.
With piston 1 in TDC adjust valves 1, 2, 3, and 5. Adjust the jamnut/screw until the feeler fits snuggly between the rocker and top of valve spring, not too tight, but not too loose.
To adjust valves 4, 6, 7, and 8 do the exact same process I stated above, but with piston 4 instead of 1.
Valves and pistons/cylinders are numbered 1-4/1-8 from the front (radiator) to the back.
This might be hard to do by yourself because the tractor is so large, its easy if you have a friend and a hand crank.
Do a compression test first. It could save you some time. If it has good spark then it should fire right up. I just got done with a fresh rebuild on a 47 M. It fired right up first time. If it doesn't seem to want to fire when cranking you may just need a tune up. I had a VAC Case that looked to good spark but wasn't hot enough. I replaced the coil a it fired right up with just a bump of the starter. These old tractors can be stubborn at time and the fix is usually something pretty simple. You may just need to be pull start it once also
ok so I adjusted the valves and no change what so ever. I am fairly confident that I did it correctly. It is rather difficult to find TDC by yourself on this tractor, so to find TDC of Piston #1 I used the notch on the crank pulley and the timing mark? I could reach spark plug hole #4 with a finger on one hand and with the other hit the starter and I cranked slowly a few times until I got a good feel of when the compressed air would be at its highest point. Compression seemed great even though i didnt throw a guage on it. Blew my finger right out of the hole like a gun. When I checked it a while ago it was very consistent at around 85-90psi if memory serves.
So now what. I am stumped!! It jsust seems strange that out of nowhere it just wont start. Could the coil be worn it where it is giving spark but perhaps not enough?? I would think that even a little spark would have the engine at least trying to fire??
I adjusted the points to .020 as well....
If it fired for a few seconds on ether, it sounds like a fuel problem. When you pulled the plugs, were they wet? Dry?
Know Your Cub, And Your Cub Will Know You.
Also, just watched a youtube video on adjusting the valves on a regular M and they bring each cylinderto TDC and then adjust the two valves for that cylinder accordingly. Just want to make sure I did that task properly. I dont want to creat more issues while trying to identify another.
Any tips on rebuilding this carb is welcomed with open arms. It seems pretty straight forward in that it seems to be mainly gaskets and one new main metering screw. However, experience is priceless so I would like to hear from those who know best.
Thanks a bunch.
You can use either sequence for adjusting the valves. The one cylinder at a time method in the youtube video works for any engine as long as you follow the firing order sequence. The 1,2,3,5 then 4,6,7,8 sequence Mike described takes advantage of knowing which other valves are completely closed when #1 and #4 are each at TDC on compression. It works for all US built IH 4-cylinder engines.
The carburetor is straightforward, with no particular traps. You need to be careful with the linkage when reinstalling it. Look carefully at the connection from the governor to the throttle plate when you pull it off, so you are sure to get it engaged properly at installation.
It seems that you have checked over all the usual suspects on your starting problem. One question comes to mind, you say you have spark at the plugs, but is it a good big, fat, blue spark? A weak spark when checking may be no spark in the cylinder under compression. You say you checked the ignition points gap, but I didn't see where you had filed or otherwise cleaned them. If you don't have a good spark, go back and file the points. Use a metal point file. If you don't have a file, burnish them with a piece of kraft paper (paper bag or cardboard). Then reset the gap and see what you have.
I assume it was this video? http://www.youtube.com/watch?v=vxi9zDwZ3Rg
You can do it either way. The way I explained it is much easier because you get half of the valves done. Also, if I'm not mistaken, the way I explained it is the way IH explains it in the service manuals.
EDIT: Dammit Jim, beat me to it haha.
Thanks Jim and Havoc, I do have spark but it isnt what I would call a good spark I will check it again. It is a 6volt system still. I am going to pull the carb off (again)tonight and clean it thoroughly and make sure all orfices are clear etc and maybe even paint it or polish it up before the kit arrives. I did take an emery cloth to the points as well as the contacts in the distributor cap and rotor.
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