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Super M Dies After Start-Up


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My dependable Super M - until very recently - dies after about 3 minutes after starting.  It starts easily, runs smoothly and then dies as if quickly fuel starved.  I converted it from 6 volts to 12 volts a couple decades ago so it has an external resistor.  I’ve drained and replaced the fuel, then used an auxiliary fuel tank incase the fuel tank is dirty & then replaced the coil with a new coil with an internal resistor (removed the exterior resistor) and it still starts easily, runs strong & smoothly and after 3 minutes simply dies.  What am I missing?  Thanks!

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Does it die all of a sudden or does it spit some pops while dying? If it dies all of a sudden, I would say it's fuel related rather than ignition related. If it dies with some popping, it will probably still be fuel related, but we had a cracked distributor cap causing issues on our F20. Once the engine got warm, it would start to run bad and it often died too. A tiny crack in the distributor cap somewhere caused this, crack expansion caused the spark to sometimes not get to the cables.
Normally, if its ignition related, the tractor wouldn't even start well I would think.

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Thank Farmall 1466.  The tractor dies, regardless of throttle setting, almost as quick as if the ignition switch was pushed in (turned off).  No popping or stuttering - dies stops running.  Every time between 3 minutes & 3 minutes 15 seconds.

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Have you checked the carburetor for contaminants ? The main jet may be plugging up , Sounds like you've done about everything electrical 

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Does it start back up within five minutes or do you have to wait a few hours for it to start 

 

Try turning the fuel off, pulling the bowl off the carb, turn the fuel on and play with the float to see if the needle valve is letting enough fuel in or if it is sticking (put a cool whip bowl on the frame rail to catch the fuel)

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Right when it dies, shut off the fuel and then see if there is fuel in the carburetor.  On a 450 I had some sort of crud got lodged right at the screen where the line goes into the carburetor and was just enough to restrict the fuel to the point that the engine used up the fuel in the carb. It would quit just like you said then start back up as fuel seeped back in and then the same thing.  For spark; invest in a spark tester so you can easily see if the ignition is working. If you have spark  unless there is a mechanical issue, then add fuel and air and it should run.

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I thinking the screen maybe plugged going into the carb on the fuel line. Also, your float could be sticking partially closed, letting enough fuel in to run and not have enough to keep running.

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All of your ideas are very appreciated.  We’re trying to finish planting SBs so I am not being as timely in getting to your suggestions as you are in helping me.  I can not find any debris, gunk or dirt in the fuel tank, lines or in the carb.  The tractor starts up very easily runs good, responds to the throttle just fine and then after 2-3.5 minutes it simply dies as if pushing in the ignition switch.  It will restart again after about 60-75 seconds and goes through the same drill.  But it won’t restart any faster then 60 seconds in case that gives you experts any useful info.

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I still think something is restricting fuel getting into the carb bowl.

Had tractor few years ago that would intermittently starve for fuel, then start back after a minute or so.  Turns out it was a fuel can flex nozzle in the tank.  When it floated by the fuel outlet, suction would pull it down onto the outlet, cutting off the flow of fuel.  When the engine died, the suction of the fuel pump would be gone, and it would float away.

Have a Super M.  When the inline fuel filter gets stopped up, it will start fine over and over, but only run for 4 or 5 minutes,  then die.  Let it sit, fuel will continue to trickle through the filter.  It'll start back, run a few minutes til the bowl is empty again, then quit.  So I really think fuel restriction of some sort.

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While float is out, pull the needle, then take a small piece of soft wood, like pine, and polish the needle seat by rotating the piece of wood around and around.

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you need to find out if its a gas problem or an electrical problem then be a lot easier to diagnose. your running out of gas as it seams. just because you changed the fuel tanks dont mean much. better check the filter in the carburator along with a carb cleaning. also when it stops remove the carb drain plug to see if any gas runs out. if next to nothing comes out you have found it!

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Thanks again for all the help!  When I converted this SM back in the 70s from 6V to 12V I included an external ballast resistor between the ignition switch & the coil.  Today I removed the external resistor & replaced the coil with an internal resistor.  Tractor still dies after a couple minutes of smooth running.  As a couple of you have said I’ll go back to the carb & remove it & more thoroughly check it out including a good cleaning.  Thanks to all of you.

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Add a fitting to the drain on the carburetor bottom and curl a clear hose up along the side of the carb so you can see the fuel level while it runs. This would narrow down the fuel or electrical possibilities 

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Thanks for all the help.  Hard to imagine what it was like working on IH equipment prior to RP forum.  Finished planting beans this early evening so attacked the SM.  Sure enough with a little bit of ether we can keep it running after it tries to stop running.  We’ll next re-hit the fuel system hard.  Thanks to all.

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On 5/14/2021 at 9:06 AM, SuperWD9 said:

Does it start back up within five minutes or do you have to wait a few hours for it to start 

 

Try turning the fuel off, pulling the bowl off the carb, turn the fuel on and play with the float to see if the needle valve is letting enough fuel in or if it is sticking (put a cool whip bowl on the frame rail to catch the fuel)

Easier to make a water level & screw it in the bottom of the carb bowel where the drain plug is. Then you can watch the gas level as the tractor is running

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I have had several tractors of this vintage do the same thing. W4, cub and a couple of "H"s. The most common cure was to remove the sediment bowl fitting from the bottom of the fuel tank and clean out the hole that feeds the bowl. The fixture is made out of some kind of pot metal and turns into a thick paste and closes the opening.

Hugh

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  • 4 weeks later...

Thanks to everyone that pitched in to help out.  Turns out the carb float was somewhat loose and at different vibrations or angles it would either stick on the carb housing in the down position or in the up position and giving two different symptoms.   Fixed and running good for two days now.  Thanks again!

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