Tue Sep 11, 2012 6:25 pm
My Farmall Cub starts and runs fine for about five or six minutes and then just dies as if I had tuned the switch off. No sputtering or any other symptoms, so I don't think it's in the fuel system. I live in Oregon, so we have 10% ethanol, but that has not been a problem in the past. I'm wondering if the problem could be in either the ignition coil or the magnito. Has anyone else out there had this problem? and what did you do to fix it? Any help would be greatly appreciated. Thanks!
Tue Sep 11, 2012 6:48 pm
Welcome to the forum! A little more information would help us diagnose.... You mention a magneto and an ignition coil...is this tractor one that has a mag but has been converted to external coil?
How long after it stalls out does it take before it will restart?
Mike in Gibsonia, PA
Tue Sep 11, 2012 6:52 pm
G'day to you
You haven't mentioned if you have an internal or an external coil. If the coil is external, touch it when the Cub dies. Bet it is probably hot. If so then the external coil may be breaking down. BTDT more times than I care to remember which is why I have gotten replacement internal coils for my mags. They are a little on the pricey side - about $60.00US but well worth the investment. Check the coil either internal or external for good spark as well. You should probably check the points and condenser. Points might be burned a bit, possibly the condenser may be bad as well. Parts breakdown is below.
Tue Sep 11, 2012 7:15 pm
Coils can die when they heat up after running awhile doesn't matter internal or external, mag or distributor. Partially plugged fuel lines can too.
I would clean the fuel filter and the intake screen in the Carb, then make sure the float moves freely. So far the cost may be a new carb gasket. If that doesn't do it I would change the coil. Basically I am cheap but I will bite the bullet and do what is next in line. Why change the coil with out further tests?
They don't last forever and I will have to change one some day. If this doesn't fix the problem t least I will have one on the shelf for the Sunday afternoon i Plan to take the Grand kids for a ride and the tractor dies. I also believe in keeping a spare condensor, points and distributor cap on the shelf too. As cheap as I am preventive maintenance as expressed in spare parts is helpful in keeping Grandpa from being embarrassed. I know my Mantra is KISS, keep it simple stupid
Wed Sep 12, 2012 3:58 am
How quickly will it re-start. Turn the switch off and on, re-start, could be in the switch or some type of short, if you have to wait a few minutes, could be starving for fuel, have to wait for about 30 minutes, could be the coil getting hot.
Wed Sep 12, 2012 11:00 am
Thanks! for all of the replies, they are all excellent ideas and thoughts to consider. I did disassemble the carburator, cleaned the screen and checked the float. All seemed to be okay. Blew through the fuel line and replaced the leaking sediment bowl assembly, and that too seemed to be okay. I also put my hand over the air cleaner intake while cranking and it drew a good strong vacuum, so I think that's okay. I did check the spark coming out of the coil wire and looked to be very strong. The coil is the internal type that sits on top of the magnito assembly, so I think I will replace that anyway along with the points and condenser. I don't want to end up stranded in a parade either. It will take a few weeks to get that done, but I will repost at that time and let know how I made out. Thanks again!
Wed Sep 12, 2012 11:58 am
When my Cubs run out of gas (and they do when I park them, I run the carb dry), or if I forget to fill the tank - they just shut off, no sputtering, etc. It acts like an electrical fault. You might want to pull the main jet out of the carb and check for a consistent fuel flow over time, if you find nothing wrong with the electrics.
Wed Sep 12, 2012 12:07 pm
I doubt it is the coil; in my experience, it takes longer than a few minutes for a dying coil to get to the point of failure. Feel the coil right after she shuts down; if it is not super hot (as in almost too hot to touch), the coil is not the problem.
Have you checked fuel flow? With the valve under the tank open, hold a cup or other something to catch fuel under the carb bowl, and remove the plug at the bottom of the bowl. You should get a steady stream of fuel. If the bowl drains, but no further fuel comes out, the problem is at the float/needle or somewhere upstream from there.
Wed Sep 12, 2012 1:22 pm
Check the fuel cap vent. Could be plugged. Symptoms sound like what happened to my cub.
Wed Sep 12, 2012 1:38 pm
My recently acquired third Cub would do the same thing. After several occurrences, I realized that it always happened when going uphill. I suspected a fuel problem and discovered that the sediment bowl was only 1/3 turn open. When I would place too much demand for fuel the engine would die. I could coast back to level ground and get it restarted right away. The fuel is an aftermarket valve of some kind with a knurled knob and it wasn't possible to tell how far the valve was opened. Once I removed the knob and turned the valve stem with a wrench about two times the problem disappeared. Be sure your fuel shutoff valve is fully open. Cost = $0.
Wed Sep 12, 2012 2:43 pm
I had a coil fail on the cub a few years back. It would run 5, 10, even 15 minutes and then would shut down like you turned off the switch. I drove around with my ohmmeter until it quit, then checked the coil resistance - it was open. Hasn't died since I put a new coil on it.
Wed Sep 12, 2012 9:12 pm
I would think that if you have a good strong spark from the internal coil then that is not your problem.
danyhulp wrote: I did check the spark coming out of the coil wire and looked to be very strong. The coil is the internal type that sits on top of the magnito assembly, so I think I will replace that anyway along with the points and condenser.
Before you change out anything, try this. Take the carburetor apart. Check the longitudinal orifice -- the little one on the end of the main jet. Then you should check the needle and cage. Hold the cage up to an open/clear window, door or look at it outside - see if it looks a little cloudy when looking through the cage. If so... then you need to clean the cage, varnish may be your problem. It sounds like fuel starvation, intermittent albeit, but probably fuel starvation due to varnish or maybe a bit of dirt in the small orifice in the jet.
Good advice is to investigate until all avenues have been exhausted then replace a suspect part one at a time and start with the least expensive such as points and condenser. I don't think it is the coil.
Thu Oct 11, 2012 11:01 am
To all of you that replied to my "just dies" question, I'm sorry that I have not gotten back to you sooner. I just wanted to let you know, I did replace the coil and that seems to have solved the problem. I took it out to he field and spent about six hours mowing weeds with no problems at all. I hope to do a better job of staying in touch. Thanks again! Danyhulp.
Thu Oct 11, 2012 1:28 pm
Hey glad we could help. Sorry it was the most expensive fix of all the possibilities but all the other things mentioned could have caused a failure like the one you experienced. One possibility not mentioned is the metal tip falling off the end of the rotor. I have had that happen on my Low Boy and on the neighbors C (it uses the same rotor)., The rivet that holds it gives up the ghost. No way to beat success though.
Thu Oct 11, 2012 2:50 pm
For anyone's future reference, check for spark AFTER the tractor dies, not when it's cold first thing in the morning.
I would bet you dollars to donuts that Danyhulp checked the spark on a COLD engine, and didn't try it immediately after the engine quit. If he had, he would have found a weak or nonexistent spark.
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