# Ford 850 only runs full choke



## Joe850 (Feb 19, 2017)

Hey all, new to the forums and new tractor owner here. Got a puzzle that I'm leaning towards carb, but wanted to get some expert opinions! 

I recently purchased a 850 with loader from an old man who was a tractor collector. He recently fell on bad health and didn't have time to tinker anymore, so was thinning his collection. He said it had been sitting for a year and ran when parked before he started having health issues, but left gas in carb etc.

I was able to crank it over, appeared to have good compression, the price was right so I took a gamble on it. Got it home and found it to have no spark. Points where corroded and coil was bad. Did a complete tune up with 12v coil and replaced wiring to coil etc. 
Started getting a healthy consistent spark then. Was able to get to run on a squirt of starting fluid for a few seconds.

Next, I noticed no fuel was getting into carb so I rebuild it(was getting to it fine, fresh gas) . Was heavily rusted inside and float needle was stuck. Cleaned all passages really good and replaced throttle shaft. Was getting gas in carb, but still wouldn't fire. Did a vacuum test with some propane and noticed leak around throttle blade arm. Forgot to replace seal there. After that it would run, but only on full choke. Took carb apart again to see if passages where block, but all seemed fine. 

*Tractor dies if even a hint of choke is removed, idle screw makes no difference.

-Here is what all has been done so far:

*Points - new gapped to .025

*Plugs - new gapped to .025

*Coil, rotor, cap and condenser new

*Rebuild carb TSX-977

*New intake/exhaust gasket

*Compression test. Wet/dry all cylinders 100-110

*Fresh Gas

I pulled the plugs during the compression test and they looked new.

I almost certain I am dealing with an air/fuel delivery problem, but not sure what it could be besides carb? 

I'm not certain this is the carb that came with tractor, I could not find any jets for the power circuit and doesn't look like most the other carbs I've seen online for the 850.
It's a Marvel-Schebler TSX-977 according to tag. 

There was a slotted brass screw plug next to the main drain plug on the bottom of the carb that I did not remove due to it being siezed. I assumed it was a secodary bowl drain, but could it have something to do with power circuit? Passages seemed clear in carb....

Thanks in advance for the help. I'm at my wits end, and dying to put this thing to work =)

-Joe


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## sixbales (May 18, 2011)

Howdy Joe, 

Welcome to the tractor forum.

There are three fuel screens in your fuel system before gas gets to the carburetor: 

1. There is a cylindrical shaped screen attached to the fuel shutoff valve. Sits up inside the tank.
2. There is a screen in the top of the sediment bowl.
3. There is a screen in the inlet elbow to the carburetor. 

Are you getting a good rush flow of fuel to the carburetor? Disconnect the fuel line at the carb inlet. A trickle flow is not good enough. Also check the screen attached to the inlet elbow to the carb.

Since you have no adjustable jets on the carburetor, you must have a fixed jet system, and the main jet is plugged. The brass plug in the bottom of the bowl must be a jet.


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## sixbales (May 18, 2011)

I checked with the guys at the YT forum. *JMOR* posted the following: "The small plug is simply plugging a hole that was necessary to drill a casting passage during manufacturing. Nothing to access there."

So, don't remove it.


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## Joe850 (Feb 19, 2017)

Thanks for the reply. 

I called the Ford/NH dealer this morning and he ran the numbers for my carb. Said it wasn't original one, but does show to be for a 172 motor, so should work.

The fuel shutoff was leaking so I removed it and replaced oring. I know that screen is clear.

The elbow screen and sediment bowl have been removed by PO and brazed in a nipple with rubber hose and inline filter. The fuel flow seems adequate to the carb. But I will try that as well.

The other thing in the back of my mind was float. I did not measure it, but eyeballed it. It was level and looked to be approx 1/4 away from top. It definitely is not flooding, but how sensitive is float adjustment and could it cause my symptoms?











sixbales said:


> Howdy Joe,
> 
> Welcome to the tractor forum.
> 
> ...


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## sixbales (May 18, 2011)

Just a few thoughts:

On a Holley carburetor, that 1/4" measurement has to be very close (within 1/32") from the gasket to the top of the floats. 

The inline filter may be for use with a fuel pump, requiring some pressure to efficiently pass gasoline?

The rubber hose may be degraded internally, obstructing flow?

Try pulling the square-headed plug from the bottom of the carburetor bowl and using a glass container, check how much gas you get over a one minute period. I would be particularly concerned of it dwindling down to a trickle flow.

Did you propane check your intake manifold.....may be loose or gasket leaking?


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## Joe850 (Feb 19, 2017)

Going to pickup some new 3/8 fuel line and the least restrictive filter I can find on my way home from work today and try that first. If that doesn't work I'll pulled carb and check float.

I replaced intake gasket, not because of intake leak but exhaust. 3/6 nuts where loose. Just to rule that out and it needed it anyway. Made no difference in performance.

Thanks for the tips. Will keep you posted. Hopefully have time to mess with it this evening.


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## Joe850 (Feb 19, 2017)

Picked up some new fuel line and a high flow glass/wire mesh type filter so I could watch gas flow. Flowing like a champ. Definitely no issue with supply. Still having same problem.

Tore into carb again and measure floats, they about 1/8 lower than they where supposed to be (so much for eyeballing). Checked center primary again while I had it apart, still clear.

Put it all back together and same problem. Only runs on full choke, even at idle. Take choke away even about an 1/4 ich and starts to sputter. Otherwise sounds like a champ. I can move throttle up, but when it gets past about 1/4 it starts to cut out. I assuming it is moving from idle circuit to primary.

I found the breakdown for parts on New Holland's website. Correct carb shows to be B6NN9510A with an adjustable primary screw and non-fixed tube. 

What I'm trying to figure out is if the primary is too large, wouldn't it be running rich? Doesn't smell rich and plugs show no signs of it. It is running lean best I can tell.

Any thoughts on what direction to go besides swapping carb? Wish I had a spare to swap it out for.


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## Joe850 (Feb 19, 2017)

Well, did some further digging and I believe the carb (tsx-977) that is on there is for more industrial applications, they where used on the larger 192ci motors for Sullair compressors etc. I bit the bullet and bought a used tsx-706 which is what it calls for, this carb has an adjustable main. Will let you know how it goes.


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## Joe850 (Feb 19, 2017)

Well, after ordering the new carb I decided I couldn't leave the old one alone and attempted to get that plug out for piece of mind. I was able to get it out with a pipe wrench fairly easily and low and behold there was a clogged jet in there. Cleaned it out and it runs as I would expect it to. Needs to be tuned, but otherwise good.

I'm most surprised about the lack of information I was able to find on this carb.... hopefully I can cancel order of new carb or I will have an extra carb lol. 

Much appreciative of your help, Sixbales. Hopefully, someone else will come across this and it will help them too =)


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