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Subject: Gas Flow

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Jack-Iowa    Posted 11-29-2020 at 18:27:37 [URL] [DELETE]        [Reply] [No Email]  
  • Gas Flow
  • I know this has been posted many times but I've never saved it and now cannot find it in the archives.

    What is the quantity of gasoline to be caught within what period from the drain plug on the bottom of the carb?

    Would this be the same or approximately so for a 700 series?

    Thanks, Jack

    JMOR    Posted 11-30-2020 at 11:59:23 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Gas Flow
  • Jack, I'm probably the person responsible for the 'flow thru carb' number of one pint in two minutes. It is a safe round compromise number. Many years experience have me running around 8 hours on 10 gallons (usually mowing w/ bush hog) and that & a calculator yields 2.67 OZ/minute or a pint in 6 minutes. HOWEVER, the Nebraska tractor test on an N-tractor shows 2.7 gallons per hour, which is 5.76 OZ/minute or a pint in 2.77 minutes. I personally have never seen such high consumption (10 gal in 3.7 hours as in Nebraska), but they are the testers and were measuring at highest work load the tractor could pull, so I have, for over a decade, suggested that a "pint in 2 minutes,or less" is a good test, based on experience operating, Nebraska test, and the fact that my two 8Ns will easily meet the pint in 2 minutes or less with a clean fuel system. So, ...if flow meets that pint in 2 minutes, you will be safely home! :)

    Jack-Iowa    Posted 11-30-2020 at 21:46:44 [URL] [DELETE]        [Reply] [Email]  
  • Re: Gas Flow
  • Thanks JMOR! I've now saved it for posterity.

    If my memory is correct the 9N and 2N tank holds 8 gallons. Back in the '40's we figured 8 hours on a tank of gas. Thank goodness they had a reserve tank on them!


    Tim Daley(MI)    Posted 12-01-2020 at 07:06:21 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Gas Flow
  • No, the Ford Tractors hold 10 gallons total. All the Manuals state this. The Sediment Bulb has a MAIN and a 1 gallon RESERVE function. Open 2 Turns for MAIN, FULL OPEN for the 1 Gallon Reserve. Supposedly. That is the way the valve and screened fuel inlet up inside were designed to function. I don't even muck with the Mason jar and stopwatch anymore. When I do a fuel flow test on a guys' carb, I simply test the fuel line first, then if it passes, test the drain plug. Either way, if flow sputters, stops and goes, or quits, you have your answer. Fuel obstruction is upstream at tank or sediment bulb or downstream at the carb. I figured JMOR or Bruce(VA) devised the 1 Pint/2 Minute Rule. Fuel system has THREE filters engineered into system. There is no need to add any more external modern type filters. They serve relatively no practical purpose and only get in the way and become a hazard, in my opinion, but it's your tractor and your money.


    Tim Daley(MI)

    Tim Daley(MI)    Posted 11-30-2020 at 07:00:45 [URL] [DELETE]        [Reply] [Email]  
  • Fuel Flow on gravity fed M/S carbs is not based on volume or size of carb. Fuel flow is the same.

    The Marvel-Schebler Fuel Flow Test on the N-Tractors has been detailed many times in posts, but I can't recall if I have ever actually read the procedure in any Ford or M/S manual as gospel documentation. Most simply say to remove fuel line from carb inlet and observe fuel flow. Any weak stream or hesitation indicates an obstruction upstream. FWIW & FYI: What has been posted and I'll again post here so the archives can be added:

    Find a 1-Pint Mason Jar and place in a coffee can, then position can under the carb. Loosen the 7/16" hex flare nut on the fuel line at the carb brass inlet elbow and gently slide the fuel line off to the side so it points down into the can. Open the Fuel Sediment Bulb Valve 2 Full Turns. Observe the fuel flow is a steady stream and you fill the can with 1 pint in 2 minutes. Any sputtering, hesitation, or failure to fill gas in the Mason Jar indicates the problem is upstream on the Sediment Bulb or in the gas tank itself. If Test passes, connect the fuel line and repeat using the carb drain plug in bottom. This is a NPT plug, tapered pipe thread; it's not a standard thread size, so do not try to use anything other than that to chase threads or replace. Often you see the hex head on the plug all rounded off from guys using pliers, vise gripes, channel locks, or simply the wrong size wrench to remove. Get the right tool. If Fuel Test passes, reset the drain plug, leave it alone, and move on -it's electrical. 99.8% of all non-starting issues are due to electrical. Many fuel issues are due to clogged systems starting with the fuel tank. 75 years of use can collect a lot of sediment, rust, and dirt. The fuel tank also has a vent on the top of it with a very small, 1/32" diameter or so air hole. If this vent gets plugged up it hinders proper fuel flow. Since the tank is not easily accessible, it's fastened to the bottom of the hood and it along with several other parts must be removed along with it so chances are the gas tank hardly ever, if not never, got flushed and vent passage cleared.

    Tim Daley(MI)

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