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Subject: 8n still sputtering...

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Jim    Posted 05-19-2018 at 20:04:58 [URL] [DELETE]        [Reply] [Email]  
  • 8n still sputtering...
  • For 6 weeks I've struggled trying to get my tractor running smooth again. I've put in 2 sets of points and condensors. New plugs. New coil. New battery. Each time, it runs good for about a minute and a half. Have to polish the points after the minute and to get it to run. Thought the new battery fixed it, but it still runs rough. Could I have a bad alternator? It's a GM internally regulated unit.

    steveVa    Posted 05-20-2018 at 15:34:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...
  • I would bypass the key switch just to make sure that is not the bad connection that makes it sputter.

    Jim    Posted 05-21-2018 at 07:49:05 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • Guys, thanks for all the input. I am soaking it all in. I'm going to try to set aside some time tonight with my meter and test leads. I will surely post back soon.

    Tony C    Posted 05-20-2018 at 12:16:03 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...

  • What do the points look like before you clean them? Look like a hot spot is forming, growing a fur coat or....?

    How bad were the points you took out initially and how did the new set look when you replaced them? Points are pretty basic. THey either have continuity closed and none open or they don't.Easily tested.

    I'm afraid to bring up the fuel system. Have you considered it may be fuel related. Engine stops for no apparent reason. You get off, find a card. Open the distributor and clean the points. In the interim enough fuel drains in to the carb get the machine running. Pretty basic question but does choking the engine when it starts to lose power help?

    A quick test of the power to the coil can be done by hooking a test lamp to the hot side of the coil and the battery ground. Ignition on light on, ya got power. If it goes out while the engine is running and the tractor dies there in lies the problem, but since it sputters and dies it may not be. Worth a test as it's easy and easy is good.

    If you have the blue plastic crimp on ends or worse Scotchlocs pay particular attention to them. Pull hard. One or another may only been hanging by a couple of strands especially if the wire is bent 90* from the connection. It may sound unnecessary but you have to start at the beginning with power supply

    The ignition switch may be bypassing current into the primary circuit. Not a full 12v but enough to overheat the points and/or the coil, when the engine is stopped with the points in the closed position.

    Does the battery discharge slowly? Not go totally dead but a little slow turning after a week of sitting? AN easy check for current draw is to hook a test light between the battery ground and ground. E.G. disconnect the ground strap and hook the light to the disconnected cable and the grounded (+ or-whichever side is grounded on your machine,) post on the battery. The light is now in series from the battery to ground. If you have current the light comes on even dimly there is a draw. Then disconnect the lead to the distributor. If the light goes out you have found a problem. Since you have a GM alternator disconnect it as I believe the exciter circuit is hot all the time.

    Or......Bypass the whole primary circuit and go directly to the battery (or a remote) for power. If the machine runs OK you know the problem is in the the primary circuit. Switch, the boars' net of wiring around the amp meter ign switch, ballast resistor, etc.

    Is the coil wired correctly and of the correct polarity?? It's 12v Neg ground I assume, and wiring a negative ground coil is pretty intuitive, but double Check it.

    It may be difficult but if you can get your hands on a known to be good distributor and coil, install them. If one or the other solves the problem go through the distributor or replace the coil.. You may have to completely disassemble it to look for problems as suggested by others here.

    BTW if you do disassemble the distributor free the advance weights if they are seized. You will be amazed at how much better your machine will run and how smoothly it picks up from idle to full throttle, no load and pulling.

    If any or none of the above help you may have to disassemble the distributor and check for loose connections, a chafed wire, a small screw or washer dancing around inside or????. That copper strip giz which can cause problems.

    Bruce (VA)    Posted 05-19-2018 at 20:35:27 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...

  • 6v or 12v?

    Front or side distributor?

    And no, your alternator isn't part of the ignition circuit, so that's not your problem.

    Jim    Posted 05-19-2018 at 20:44:16 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • 12 volts. Side mount distributor.

    Bruce (VA)    Posted 05-20-2018 at 05:02:42 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • Are you using a 12 volt coil or a 6v coil w/ a resistor? (see tip # 30)

    Confirm that you have voltage to the coil. Battery voltage, points open. About half that if the points are closed.

    Do you have battery voltage across the points when they are open? (with the points open, put one probe on one side of the points & the other probe on the opposite side of the points) Verify the gap on the points at .025. Then, dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. (I always spray my feeler gauge blade off w/ contact cleaner.) Make sure you have voltage across the points, as in past the insulator on the side of the distributor. As Kevin said, that is a very common failure point on sidemounts, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. If you find the short there, the Master Parts catalog lists everything you need on page 154. You can make the strip and you could also make the insulators as well. But, somethings are just easier & in the long run cheaper to buy. Get the strip, 12209, screw 350032-S, 12233 bushing & 12234 insulator & just replace it all.

    K.LaRue-VA    Posted 05-19-2018 at 21:20:45 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...
  • Had similar problems. They didn't go away until I did away with that infernal collection of junk that transfers the coil wire to the points. Ran a new coil wire thru a grommet connected directly to the points, and it's been running fine ever since.

    Jim    Posted 05-21-2018 at 19:02:56 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • I checked everything you guys suggested and still no luck. Everything checks good. I replaced the key switch with a known good one and like EVERYTHING I've replaced so far, it seems to make it run good for about a minute and a half and then it starts running bad again. I've never been so frustrated with a machine. I've ran and restored old pickups for 45 years and never had anything I couldnt figure out in a day or two. This makes 2 months. The only thing left to do is to rewire it.

    Tony C    Posted 05-22-2018 at 08:49:19 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...
  • Good morning Jim,

    You never mentioned the fuel system. Did you choke it when it was dying? What was the result? Did you check the fuel system, tank to venturi? HAve you tried spraying starting fluid in the carb when it starts to die?

    It's been my experience generally that when an engine slowly loses power and dies it's a fuel delivery problem. Electrical, it shuts off like the key has been turned off, which in effect it has. I only mention this as you say it sputters and dies. If you haven't gone through the fuel system as thoroughly as you went through the electrical system you haven't done everything.


    Jim    Posted 05-22-2018 at 11:19:23 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • Great point. I actually started with the fuel supply 6 weeks ago. Choking does keep it running a milisecond longer. It seldom dies...just runs roughly. Can't give it anygas...it just bogs down and sputters.

    Tony C.    Posted 05-22-2018 at 12:27:25 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...
  • Good gas, correct? How far did you go with the fuel system? Disassemble and clean out the carb and adjust it correctly. Possibly a chunk of dirt under the main jet? Needle valve? Or float sticking?

    Bogging and dying upon acceleration can be caused by fuel shortage. Too much air too quick vs. amount of fuel, you get the idea. Picking up slowly and if you have to tickle it, advance weights frozen. Usually that only makes it just a little lazy picking up the rpm and maybe not getting full power.


    Jim    Posted 05-23-2018 at 08:48:34 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n still sputtering...
  • I took the carb apart...twice...cleaned it with carb cleaner and air pressure. I also took the fuel shutoff valve off and blew it out. Strange thing though...it idled faster than normal and I didn't change the idle stop screw setting. It's going to be a couple of weeks before I can get back to it, bUT I think I'm going to put one of the good kits in the carb.

    Tony C    Posted 05-23-2018 at 11:17:03 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n still sputtering...
  • IIRC you have replaced the condenser ......twice. Gotta believe that isn't the problem.

    Still a puzzle wrapped in an enignma. When you disassemble the carb pay attention to the float height adjustment. Gasket on. ....and for any binding however slight in the float pivot and shaft. Float height .260" factory. Most set it at .250 above the gasket. It's not a six barrel Holley so .010" probably isn't that critical. This may be redundant as it seems like you have had your fingers in these and more complicated carbs in the past.

    A couple of years ago I stumbled on Kevin LaRues' article on myfordtractor IIRC detailing rebuilding the MS carb. Enough information to cause sensory overload but excellent information. He covers it all. Lots of pictures too.

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