ford 8n carburator problem

I bought a 8N last year and it ran ok till you drove down a steep grade.It would suddenly just quit.I thought the float was sticking so I took the carb apart and it looked fine.(it was an aftermarket new carb.)I did this at least 4 times so I finally found a used marvel schebler carb.So I cleaned it,put a new kit in and set the float according to videos I watched.Now it also dies going down steep grade at low throttle speeds.Also on level ground at low throttle the engine will speed up a little then fall off continually till you open throttle up more.Can anyone tell me what the problem could be and how to fix it.I might also mention that when working such as mowing or pulling a disc it does ok with the throttle opened up more.When I cleaned the used marvel carb I sprayed with carb cleaner and blew it out with the air compressor.As far as I could tell all the parts were still in the used carb.In fact they had to take it off the other tractor when I bought it.

Thanks for any help or suggestions.

Did you perform a fuel flow test first to see if the carb is even getting fuel? The issue could be in the sediment bulb assembly. Get out your Essential Owner/Operator Manuals as there are detailed instructions on how to rebuild the carb. Videos don't always cover all the details, often done amateurish. Read the manuals. M/S is the preferred carb was used OEM, a Zenith is OK, but several aftermarket units are junk out of the box. Which Marvel-Schebler carb did you get? Since you've been thru so many carbs all resulting in the same problem that should be a clue something else is the root cause. A plugged vent hole -try removing gas cap and see if it changes. Carb not adjusted correctly -read manuals. Governor not working or needs rebuild, but that would be the last thing to check.

FORD 8N TRACTOR ESSENTIAL OWNERS MANUALS:

Tim Daley(MI)


Tim Daley(MI)

After I determined my fuel supply was okay and it was in my carb I checked for rebuilt kits. they ranged from 20 to 40 bucks. I checked on new carbs and found one shipped for 58 bucks. no brainer for me as I am not very good on rebuilding carbs. put the new on and boy did it start nd run good. I did put an inline fuel filter in it just before the carb. Put new carb on my 960 7 years ago. starts right up and runs good in any weather. good experiences for me anyway. good luck

FWIW: The basic fuel flow test determines whether the carb is getting sufficient fuel flow or not. I don't know what you mean by "...my fuel supply was okay...and it was in my carb..." -either the carb is getting fuel or it isn't. Do it like this: Engine cold, coffee can under carb, open drain plug on bottom then open the Sediment Bulb Valve 2 turns. Fuel flow out the drain should be 1 pint in 2 minutes. Any hesitation, starting & stopping, or a weak flow means blockage could be inside the carb. To be sure, replace drain plug, go to the fuel inlet line on the brass carb elbow on the carb, and loosen it with a 7/16" flare nut wrench, then gently pull the line off and away from the carb elbow so it is pointing down. Place the coffee can under it. Go to the Sediment Bulb and open the valve 2 Full Turns. Once again observe if fuel flow produces 1 pint in 2 minutes without hesitation. If it stutters or appears weak (flow should be about a pencil thick steady stream) then the blockage is in the Sediment Bulb. When performing either test, if weak or hesitation is observed, try removing the gas cap and see if it improves. If so, then the gas tank vent hole is plugged. It is a on the top center of the tank and the entire tank needs to be removed in order to get to it. It is about a 1-2 minute job to clear the vent, but a several hour job to get the tank off. If gas cap removal doesn't affect the flow, then problem may be in the two screens in the sediment bulb assembly. One screen is soldered on to the fuel inlet port on top of the assembly -the end that is up inside the tank. The second is on top of the glass bowl and gasket. The third screen is soldered onto the brass fuel inlet elbow. All three need to be removed and cleaned or replaced. The only part that gets bad in the sediment bulb is the valve stem. It also is a lot cheaper than buying a whole new assembly. If the screen on top of assembly or the brass elbow screen are missing, get new ones. There is no logical reason to add any other in-line fuel filter -there are three in the OEM system. It is also not advisable to use copper, plastic, aluminum, nylon, or rubber fuel lines -get the correct steel line from Bulb to Carb...they're made exact and pre-bent to fit perfectly. There are some here who will rebuild your original M/S carb; me and Royse for two examples. Just ask. I advise to never just take any new part out of the box and put it on. You got lucky this time.

Tim Daley(MI)