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Subject: Help - 1951 8N Not Catching

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Keelan    Posted 06-14-2021 at 09:13:06 [URL] [DELETE]        [Reply] [Email]  
  • Help - 1951 8N Not Catching
  • Hello!

    I was tasked this spring with getting the 1951 8N my grandfather purchased back in '56 up and running. Its been temperamental to start for at least a decade, and this spring it appears to have given up.

    A little background:

    We use this tractor mostly for brush hogging, hauling logs, and pulling around a small trailer for property maintenance during the summer months. Its kept in a shed all year, so in general is in fairly good condition.

    My father has been looking after the tractor since my grandfather passed away, and while he's fairly handy, he's not overly mechanically inclined and his maintenance has mostly extended to greasing the fittings, changing the oil, and replacing the odd part (spark plugs/distributor cap, etc).

    My background is in mechanical engineering, but my professional career veered off into the commercial lighting industry, so while I'm well grounded in electrical/mechanical principals, my knowledge on engines and specifically those from the 1950's is lacking.

    So here's what I can tell you:

    The tractor is still a 6V positive ground system, and over the years it takes a lot of cranking by the starter motor to get the engine to catch. Especially when its cold out (10-15C), its pretty easy to kill the battery without the engine ever firing up. Recently it also seems that the spark plugs foul with carbon deposits fairly quickly.

    This spring when getting it up and running, I finally managed to get the engine to catch, but it was struggling to develop power. I let it run for a while, and then managed to drive it around a bit to see if I could work something through its system, however it eventually sputtered out and died. I was unable to get it running again.

    So here's what I've done to date:

    Checked the carburetor and air filter to see if there was anything interfering with supply to the engine (possibly too rich resulting in the carbon fouling). Nothing seems amiss, and fuel is getting into the carburetor from the tank (flow does not seem impeded). I also purchased a new battery and spark plugs.

    Still was unable to get it to start.

    I had a mechanic come to take a look at it over the weekend (older fellow, been working on tractors for at least 5 decades), and here's the result of about 3 hours:

    Getting a spark
    Checked the timing (looks accurate)
    Getting compression
    Replaced the spark plug wires
    Replaced the points

    We eventually pulled out the ignition coil, and it was listed as a 6/12V unit (for 12V use w/ external resistor). This didn't sit right with my mechanic, so he suggested we replace it. In speaking with my parts supplier, it seems like this is fairly common these days, and while I'll replace it anyways, it doesn't sound like this is the likely source of the problem.

    So here's where I need some guidance. I'm not sure what other diagnostics I should perform, and neither my mechanic nor I can seem to figure out what the fault is that is causing the engine to not catch. I'm up to work on it again in a few weeks, so any/all suggestions of things to check would be welcome.

    Thanks in advance!

    TheOldHokie    Posted 06-17-2021 at 09:58:19 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Help - 1951 8N Not Catching
  • I am always suspicious of the fuel in situations like this. How long has it been sitting in that tank?

    You have spark so that points to fuel or compression.

    A couple judicious squirts of fresh fuel in the carb intake will generally get a fuel starved engine to start and run for a second or two. Might want to clean the plugs before trying to make sure any water or other crud has been removed.

    TOH

    Steve Dabrowski    Posted 06-16-2021 at 19:16:39 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Help - 1951 8N Not Catching
  • You might try taking the carburetor off and completely cleaning it, remove the jets and all pieces that come out, give it a good scrubbing with carb cleaner and clean all the passages for both the main intake jet and the idle ckts. Put all back together with good gaskets, a new needle valve, etc. when back together set the main needle 1-1/2 turn open and the idle about 1/2 turn. My emphasis is on clean-it is hard to see if the passages that contribute to starting are working so they must be clean.

    There are a couple of good guides to cleaning in the How To's here as well as a manual for the carburetors themselves that are woth reading to understand the importance of the various areas of the units.

    Other area is vacuum leaks, make sure the manifold gaskets are good and seal the intake as well as the gasket for the carburetor to flange.

    Just sounds like a fuel system issue.

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