1966 farmall 140

I have 1966 Farmall 140 Tractor that will run if I spray either in the air breather but won't run as soon as I stop spraying either,I have rebuilt the carb but the tractor still won't start.

You need to disconnect the gas line at the carburetor and see if there's a full stream of gas from the tank. Hold a clean container and catch the gas. If there's just a trickle of gas there's dirt or rust blocking the gas flow.
If there's an inline filter you probably need to remove that if it's not for a gravity flow system.

Did you soak that carburetor in carb cleaner and clean all the jets? This is very important since this gas may have gummed up your carburetor inside and is blocking the gas flow to your engine.

Hold your hand over the throat of the carb and see if there's good suction on your hand while a helper make's an attempt to start the engine. If there's very little suction you may have a vacuum leak. You need good manifold vacuum to suck that fuel into the engine. Spray a little bit of that starting fluid around the intake manifold gasket between the engine and intake manifold while someone makes an attempt to start the engine. Be sure the ignition switch is in the on position and see if the engine fires. If it does your intake is leaking and may need tightening or replace the gasket. Hal
PS: Don't use too much of that starting fluid as you can damage the engine.

Not sure about the 140 but I've got a Super A that also has a screen in the elbow that connects the fuel line to the carb. You have to take the elbow off to see it. If you have an elbow, check it too. Mine would not run and it was completely plugged.

FWIW

slim

I forgot the screen it could be clogged. Hal

I remember WD40 used to be the spray of choice for vacuum tests, but now I'm thinking I heard somewhere that they changed the formula and it isn't flammable enough to be used for that anymore. Am I "misremembering?"

WD40 would be a lot less harmfull than ether- in fact, if you had deep enough pockets, you could have a kid run along beside you and spray it until the hay was all baled.

I don't think his legs would hold up. Hal

the screen was the problem with my cub lo-boy

Just talked to a friend who is a good mechanic about a issue with his 140,,,, like yours would not run with out some help,,, claimed he rebuilt the carb and it was clean,,, he said no matter what are how much choke he applied it would not wet the plugs,,,, I ask about the bowl gasket if it had been sucked in near the air intake,,, got a yes and he used the old gasket just tried to make the old one work,,, a new gasket fixed it

Float valve may be sticking shut, soft tip needle valves stick often.