Fordson New Major gas running lean

[Fordsoll]

Hello, I have a Fordson New Major Gas tractor that will run too lean with no choke. I checked for air leaks using starting fluid, propane and carburetor cleaner and could not find any. I have boiled the carburetor and sprayed every passage out with carb clean and compressed air. My main issue is that the manual says to remove the metering jet I need a special tool, and I cannot get to the main jet without removing the metering nozzle first. This is a fixed jet carburetor so I can't adjust it at all.
I also confirmed that I have good fuel flow from the pump to the carb.

 

[DanielW]

I wouldn't worry about removing the jet - between spraying with carb cleaner, soaking, and poking through it with a very thin wire (stripping the plastic coating off a twist tie works well) you'll get that jet as clean as can be. I never remove the jets when doing a carb job anymore - I see no point. Every week it seems there's a posting here (usually on the Ford N forums) by some chap who's tried to remove a jet on his old carb and broken/stripped something trying to get it out. As long as you can poke a wire though and blow it out, it'll be just dandy. But I would make sure you can poke through it: If the gunk is really caked in there, boiling and blowing it out often isn't enough.

I had the same lean issue on one of may new gas majors. The gas majors weren't very popular compared to the diesels, but they are great tractors (I have three). My lean issue was fixed when I rebuilt the carb with new gaskets and ensured the carb halves were mating tightly (I put a piece of very fine sandpaper on a piece of glass and drew the mating surfaces over it a few times to flatten them out and clean them up).

Were you able to get new gaskets for your carb? If so, did you have to make them yourself? Rebuild parts for those carbs are pretty much impossible to come by (another reason why it's best not to risk wrecking a jet trying to remove it). I had a few gaskets kits for those carbs made; I drew the gaskets in CAD and had a local laser-cutting place make a few sets. Might still have one around if you're interested - I'll take a look. But they're not hard to make yourself if you need to.

What kind of adjustments have you done to the main jet to try and make the mixture richer/leaner? I can't remember what the nominal adjustment in the manual is, but I know I had to tweak mine to run properly. Have you checked the torque of your manifold nuts? The nuts holding the intake manifold on often work loose and cause it to suck air right at the block. I have better luck testing for leaks with oxygen than I do with propane/acetylene/starting fluid, and even then it's not always a perfect test. Often a slight leak will be present that's not detected with the old acetylene/propane/oxygen trick. Especially on an open engine like that with the rad fan blowing so much air by it constantly: the propane/starting-fluid/oxygen you're using to test probably gets mostly blown away before it gets a chance to be sucked into the leak.

 

[Majorman]

Manifold gaskets would be my first port of call if the carb has been cleaned. The early carb had an adjustable jet but they soon changed it to a fixed jet. When I had the problem on my petrol/kerosene version it was the manifold gaskets.

 

[Fordsoll]

I put new manifold gaskets on before I posted this and there wasn't much of a change. I had to make a new gasket for my carb, I had already resurfaced one side but didn't do the other because my piece of sandpaper was in the center of the glass and the bend for the intake got in the way. I will resurface the other side and see if it works. The carburetor is also leaking a little bit of gas from the gasket when I over prime it. I will also make a better gasket because at the time I didn't have the gasket material I wanted to use.

Unfortunately It has a fixed main jet but hopefully it won't be an issue once I have this sorted out.

 

[Fordsoll]

I made a new gasket and put some permatex aviation gasket sealer on (light amount). Still wants to run at half choke, I should note that it is missing the air cleaner assembly. Would it restrict it that much? I assume a clean air cleaner wouldn't restrict it like half choke would. I should also note that this thing has a chevy hei distributor on it unfortunately, Does anyone know where I can get something with points that fits this?

 

[560Dennis]

I had trouble With the idle circuit on the c Farmall , was plugged up not amount of carb cleaner was going to remove it ,it was a .04 hole , that needs a .04 drill to hand twist it .clean it out.
Not famil with what’s on the Fordson for carburetor.
The other thing I do is,I’ll mention ,I put a vacuum gage on the tractor to troubleshoot issues with the fuel and mech issues.
should have 18 to 21 inches of hg on gage with steady needle . If not then it will point out the problem With a troubled chart .
last thing is how the timing ?

 

[Fordsoll]

I rewired the tractor because the old wiring was very bad, and I also did some work on the distributor and as I was setting tdc I noticed that the spark plug is half the length of what it should be. I ordered new correct spark plugs for it and between the rewiring, distributor work, and the spark plugs it should run great.

 

[BobsOld52]

I know the problem. I have a 1952 "petrol" version that I just rebuilt the motor and when rebuilding the carb noticed that there was a brass tube, shown in the Owners Manual only, not in the parts book, called the High Speed Air Bleed Tube. It did not fit well in the carb and came out easily. Long story short, in the winter especially, the engine needed a lot of choke to run OK, so I decided to check the float level etc and discovered to my dismay at the tube was not there... I was able to fabricate one by getting some 1/8" brass tubing from a model shop, bending it and drilling a small 1/16" hole in top. I soldered a small collet onto the tube and it is now a tight fit in the carb body. The engine now works better than ever, no choke needed at all. See the attached photos. Hopefully this is your problem. Cheers, Bob

 

[BobsOld52]

I made a new gasket and put some permatex aviation gasket sealer on (light amount). Still wants to run at half choke, I should note that it is missing the air cleaner assembly. Would it restrict it that much? I assume a clean air cleaner wouldn't restrict it like half choke would. I should also note that this thing has a chevy hei distributor on it unfortunately, Does anyone know where I can get something with points that fits this?

There are some Lucas distributors that will fit it. There is a fellow in Engand called "The Distributor Doctor" and he knows all about these distributors and what is equivalent. The original distributor is a Lucas DM4

 

[Fordsoll]

I seperated the top and bottom half of the carburetor and there were no brass tubes that I could see. Should the brass tube be obvious? or is it in a hole.

 

[Fordsoll]

Is the brass tube supposed to come out of the hole in the first picture? Its the hole labeled high speed air bleed in the manual but it doesn't mention a tube. Does it just stick straight up into the carb opening?

 

[BobsOld52]

I was unable to attach pictures in my first post. The image is from the Owners Manual, not the parts book, and the other photo is the one I made. The tractor serial number is 1229358, so an early one from 1952. Hopefully this works now...

 

[BobsOld52]

The pictures do not seem to be getting attached, trying again...it seems I cannot attach pictures?

 

[BobsOld52]

Lower file size images hopefully works...
I noticed in your carburator that you do not have a screwed in "jet" in the body of the carb, just like mine, on the right side of the tube, in the photo of my home-made tube. The newer carb version in the parts diagram you showed has a jet threaded into the carb body where my carb has the tube inserted. The Owners Manual image I shared shows the adjustable main jet, which I do not have, but I certainly did have the bleed tube. Hopefully this solves your problem.

 

[BobsOld52]

In your parts book image, it is referred to as the "High speed air bleed"

 

[Fordsoll]

Thank you for that, unfortunately I have tried the fix and the engine still needs choke. I realized that when I start the tractor, the governor immediately closes the throttle, and the engine still runs at high rpm. Obviously I have a major vacuum leak. I pulled the fan pulley and used propane again and it only runs good if I put the propane into the carburetor opening, so no leaks from the outside. I'm thinking that maybe I have a bad intake valve, so I will run a compression check, then pull the valve cover to see if any valves are bent.

One other thing is that between the head and block, I see ugly red rtv silicon, obviously someone has done some hack work on this tractor unfortunately. I may have to pull the head.

 

[BobsOld52]

Too bad the high speed tube did not work. I would be interested to know what the compression is certainly. You could also try a vacuum gauge on the line to the distributor vacuum advance. Good luck, let us know what you discover.

 

[BobsOld52]

You might also want to check float level. It should be 16mm from the top of the carb to the gas level.