carb has me stumped - Farmall BN

jCarroll · Jan 18, 2023

Carb is a MS fixed jet.
Tractor runs for 3-5 minutes and stops being gas starved.
Wait five minutes and it'll start and run for another 5 minutes.
I put a tube on the drain plug and gas level was an good inch below bowl gasket.
I expected it to be half-an-inch higher.
Removed carb bowl and float seats .125 higher than spec. This makes me think gas level ought to be too high, instead of being too low.
What am I missing?
What should my next test be?

TIA

RogerinIowa · Jan 18, 2023

What was flow rate out of drain plug location?

Charlie M · Jan 18, 2023

I'd make sure the float is set to the correct height and if that doesn't fix it I'd be looking at a problem between the carb and gas tank. There may be a screen going into the carb, there should be a screen in the sediment bowl and its possible something is floating around in the tank and partially plugging the outlet.

rustred · Jan 18, 2023

U need to check your fuel flows, coming out of tank after sediment bowl. Then at the end of the line before carb, then running through the carb out the bottom. As for the float setting turn the top half upside down and eye the float up if its sitting level. Float level means float level. So float sitting higher than spec. Means its too low. Because you are measuring from the top half upside down to the bottom of the float. The gas should be like 3/4 the way to the top of bowl when installed and needle closes. Do these checks report back.

flying belgian · Jan 18, 2023

Vent holes in gas cap.

stoughtonfarmboy · Jan 18, 2023

I second the idea of blockage. Years ago my Farmall Cub would run for awhile then die. Wait a few minutes and it would run and then die. Turns out there was a big horse fly in the gas line.

Ken

used red MN · Jan 18, 2023

Post by Charlie M ..screen going in the carb.. Filter screen elbow key 50 on attached. Or as others have probably mentioned, something plugged in the sediment bowl under the tank. Also debris plugging the in let to the sediment bowl in the gas tank. Look in there with a good flashlight.
CNHI Farmall BN parts diagrams

grandpa Love · Jan 18, 2023

100 percent sure it's running out of gas?? Could be a coil giving up or the condenser. Are you sure it's fuel starved?

grandpa Love · Jan 18, 2023

As soon as it dies, jump off, remove plug out of the bottom of the carb..... Got gas in there?? If so ain't running out of gas.

Janicholson · Jan 18, 2023

Two issues: The float is measured when the carb (without bowl) is upside down. If too high when upside down it will be too low when right side up.
Second: fuel flow can be compromised at the tank outlet, the valve orifice at the sediment bowl, the screen in the sediment bowl, the screen in the fitting at the carb inlet, and finally at the needle itself. Flow out the carb drain should be steady and make 1/2 quart per minute or so. It will be fast for 2 seconds, then steady for at least one minute of sampling. Jim

wore out · Jan 18, 2023

Install a ''hose barb'' in the bowl drain and attach a piece of clear plastic hose looped upward and safely secure it to avoid a gasoline leak.

Now you can observe the static fuel level and if and how much it drops when the engine is acting up.

jCarroll · Jan 18, 2023

This is how I determined the gas was an inch lower than I thought it ought to be.
But I checked it static - not running.

jCarroll · Jan 18, 2023

Have the new black, tall IH cap.

jCarroll · Jan 18, 2023

Too low. And too low out of the sediment bowl. No obvious dirt.
Draining the tank to remove sediment bowl and go step by step to carb.

It's looking more like a fuel delivery problem than a carb problem.

Why don't I start with the easy obvious stuff ???

Curt Cooke · Jan 18, 2023

Wild shot. The bowl in the carburetor must vent. There must be passage between the bowl and the top half of the carb. If you've replaced the gasket between the top half and bottom half of carb, beware that the gasket could be plugging that passage. When you get a kit it comes with more than one gasket and if the wrong gasket is used, that passage may be blocked. It's a good sized hole, can't miss it.

Leroy · Jan 18, 2023

Remove cap and try as it may just be a bad cap.

gbs · Jan 18, 2023

i had a chip of paint above the needle valve seat do the same thing

redtom · Jan 18, 2023

That screen in sediment bowl is fine enough that a few drops of water will spread over it and block it off. All I can offer is start at the beginning, flow from sediment bowl, take bowl out of tank and drain tank completely. Catch gas in jar and check for water. Dry tank out and start over. I've found lady bugs jammed inside sediment bowl fittings.

rustred · Jan 18, 2023

Before you remove the sediment bowl from tank, just remove the bowl and check it where the gas flows out. I have even seen many just get corroded from that aluminum pot metal. Poke it out with a nail and some air. Then turn the gas on and it should be flowing good. But your choice if u want to remove the whole thing to give it the once over.

gene bender · Jan 19, 2023

drain the gas tank and the remove the sediment assy blow it out as something is stopping the gas flow to the carb you probably will find the trouble there when draining the tank. When tractor stops have you removed the drain plug on the carb it will be dry thats why the engine stopped wait and see when gas will start flowing it probably will be just a small amount.

carb has me stumped - Farmall BN

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