Ford 640 carburetor trouble

Ford 640 carburetor trouble. I have a 1955 640 with a replacement carburetor from Stiener. It is a Marvel-Schlebler TXS 580 copy. The trouble is that the fuel flows through the carb and into the air cleaner tube. This backs up through the intake manifold and into the crankcase. What causes this and how do I fix it. This problem existed with the original carb wich prompted me to get the new carb. Thanks for any advise :!:

That is caused by one of a number of problems.
#1 bad float.
#2 float needle not closing as it should
#3 bent float so the float cannot move like it should
#4 needle seat not as tight as it needs to be so is leaking.
#5 dirt/rust in the needle seat cause the needle not to be able to shut off the gas

As young fella told you your float valve is not closing. This can be due to a few different things but most likely dirt in the valve. The dirt has to come from your gas tank. There is supposed to be a screen inside the tank to catch the dirt. Check the inside of your tank with a light on a flex tube. If no screen get a replacement outlet tap. The screen comes with it. If the tank has a lot of crud in it clean it by suctioning the gas out. Next go to your sediment bowl and check for a screen there. If no screen order one along with a couple of gaskets from this site. You can flush clean fuel through the carb to clean it by removing the drain plug on the bottom. While it is out thread in a 1/8 pipe X barbed adaptor with some vinyl tube on it to check the gas level in the float bowl. it should be 1/4 inch down from the mating surface. If it is more than 1/8 off you will need to remove the float bowl and adjust the float by bending the mounting tab.

Being it is a new carb, 99% chance it is trash coming down from the tank.

Like showcrop said, there should be screens in the tank, in the sediment bowl, and usually in the fitting at the carb. Some people add an inline filter. If you do, be sure it is a screen type, not paper. Paper is too restrictive for gravity flow systems.

If the tank is flaking rust, or contaminated, take it off, rinse it out with E85 gas.

If it is severely rusted, it's days are numbered. Might consider replacing it with a new tank.

Whatever solution you choose, the fuel valve should always be turned off when not in use. In severe cases gas will overflow into the crankcase. Might check to be sure that has not happened. Diluted oil can spin bearings!

(quoted from post at 15:53:38 09/02/20) Being it is a new carb, 99% chance it is trash coming down from the tank.

Like showcrop said, there should be screens in the tank, in the sediment bowl, and usually in the fitting at the carb. Some people add an inline filter. If you do, be sure it is a screen type, not paper. Paper is too restrictive for gravity flow systems.

If the tank is flaking rust, or contaminated, take it off, rinse it out with E85 gas.

If it is severely rusted, it's days are numbered. Might consider replacing it with a new tank.

Whatever solution you choose, the fuel valve should always be turned off when not in use. In severe cases gas will overflow into the crankcase. Might check to be sure that has not happened. Diluted oil can spin bearings!

Click to expand...

All of these suggestions are good, however, the tank was removed and cleaned during the examination of why my problem occurred. There is a screen in the tank which was removed and cleaned, the sediment bowl is new with a screen in place (no debris showing in the bowl). the carburetor is new (it may have manufacturing debris in it) and can not be returned if it has been opened up. The crankcase has been purged (3 times) by having the tank of gas run through it and being expelled all over my shop. complete oil/filter change after each episode. I will try several of the remedies suggested by you and other respondents before tearing it down once again

(quoted from post at 05:53:26 09/03/20)

(quoted from post at 15:53:38 09/02/20) Being it is a new carb, 99% chance it is trash coming down from the tank.

Like showcrop said, there should be screens in the tank, in the sediment bowl, and usually in the fitting at the carb. Some people add an inline filter. If you do, be sure it is a screen type, not paper. Paper is too restrictive for gravity flow systems.

If the tank is flaking rust, or contaminated, take it off, rinse it out with E85 gas.

If it is severely rusted, it's days are numbered. Might consider replacing it with a new tank.

Whatever solution you choose, the fuel valve should always be turned off when not in use. In severe cases gas will overflow into the crankcase. Might check to be sure that has not happened. Diluted oil can spin bearings!

Click to expand...

All of these suggestions are good, however, the tank was removed and cleaned during the examination of why my problem occurred. There is a screen in the tank which was removed and cleaned, the sediment bowl is new with a screen in place (no debris showing in the bowl). the carburetor is new (it may have manufacturing debris in it) and can not be returned if it has been opened up. The crankcase has been purged (3 times) by having the tank of gas run through it and being expelled all over my shop. complete oil/filter change after each episode. I will try several of the remedies suggested by you and other respondents before tearing it down once again

Click to expand...

Well, now that we know the story, It comes down to an internal problem in the carburetor, poorly adjusted, tab on the float bent, float out of line and rubbing on the side of the chamber etc. so I would send it back.