Petrol leak at carb.

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Model T Ford Forum: Forum 2012: Petrol leak at carb.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Ian Dean on Wednesday, July 25, 2012 - 11:48 am:

Hi folks from sunny France. I have acquired 1923 T with a utility body. It was barn stored for 15 years. I have cleaned out the fuel tank, fuel lines and carb., and the engine now runs. I do have a problem though...... Turn on the fuel tap and there is no fuel leak, start the engine, shut the choke and let it idle. All OK.Shut off the engine and petrol starts to pour out of the carb (a Ford NH type)from a small hole opposite the choke stop screw (on the side nearest the engine).

Any ideas for a cure please. Thank you.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, July 25, 2012 - 11:59 am:

Sounds like the float needle. When the valve is off at the tank, no fuel will flow in the line toward the carb, but when the valve is open, the fuel flows toward the carburetor. It might be just a slow drip inside the carburetor and not noticed while you are driving or running the engine, but when you shut off the engine, the gas keeps on flowing until you turn off the valve at the tank.

Turn off the gas at the tank. First thing to check is take off the carburetor bowl by unscrewing the brass bolt at the bottom, then remove the brass pin holding the float in place. Now remove the float and the needle valve should drop out. There might be some dirt in the needle jet. Remove the dirt and replace the needle. The needle should move up and down freely without sticking. Now check the float. It should be lightweight. It is hollow and full of air. If it is full of gas due to a leak, the float must be replaced. Check by floating it on water or other liquid. If it sinks, replace it. If the float is good put it back in place and put the bowl back on and try again. If it still leaks, you will need to replace the needle and seat.

Note, some of the newer fuels become sticky as they evaporate, and if the car is parked a long time, the float and or needle will stick. That could be the problem. You might need to disassemble the carburetor and thoroughly clean it. and replace the gaskets.

Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Wednesday, July 25, 2012 - 12:13 pm:

Two things to start with. Make sure your needle valve seal between the needle valve and seat is good and tight. If you can hear air getting by the seal between the needle valve and seat while lightly holding it closed and sucking on the fuel inlet, then you need a new needle valve and seat. Also, be sure your float is adjusted to 15/64" to 1/4" from the machined flange to the top of the float, opposite the hinge. Jim Patrick




Top of pagePrevious messageNext messageBottom of page Link to this message  By Ian Dean on Wednesday, July 25, 2012 - 12:14 pm:

Thank you very much for that helpful and speedy reply. I had stripped down the carb and removed the needle valve for cleaning. I checked that the float floated on water - it did - the cone shaped valve that dropped out looked clean, I buffed up lightly and re-assembled. With new gasket and goo.

Question: Is the seat itself removable to clean or renew?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Wednesday, July 25, 2012 - 12:25 pm:

Yes the float needle valve seat is removable using a standard screwdriver wide enough to fit into the opposing grooves on each side of the seat. Has to be in case the seat is bad you'll need to buy a new seat and needle valve which arrive in a matching set. Attached is an illustration on how to make a float adjustment gauge. Jim Patrick





Top of pagePrevious messageNext messageBottom of page Link to this message  By Ian Dean on Wednesday, July 25, 2012 - 12:26 pm:

I have answered my own question! I find that the English Ford T Register sell replacement valves and seats. I also see from the drawing sent by Jim Patrick, that the seat comes out.

Thanks once again, I will let you know how it goes!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Wednesday, July 25, 2012 - 12:35 pm:

PS. The cone shaped valve that dropped out is the float needle valve to which we are referring. There is another very long needle valve (choke adjustment valve) which adjusts the spray of fuel going into the intake. This remains slightly open so the seat for this is not as important as the seat for the "cone shaped valve" and seat. Be careful when buffing sanding or cleaning these needle valves as they are very precise and if you change the pitch of the needle, it can ruin the needle valve.

Whenever the float bowl has filled up to the proper level with petrol, the float rises and shuts the float valve off by pressing the float valve against the seat. If the seal is not good, petrol will continue to flow through the closed valve and onto the ground. In addition to a good float valve seal, that is why the float adjustment level is also so important. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By John B Joyce on Wednesday, July 25, 2012 - 12:50 pm:

Those seats are often frozen in place and it's easy to booger up the slot with a screwdriver. Heat up the seat area with a propane torch and let cool. should come out easily then. There's a gasket under the spray needle seat you'll need to replace if you use heat . Good luck. John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Wednesday, July 25, 2012 - 12:58 pm:

Sometimes that seat is so stuck that it won't budge when you try to turn it out. Attempts to get it out just chew up the slot. When it's stuck that tight, apply the "heat wrench." Just heat that part of the carburetor body until it starts to turn red, then let it cool. After that the seat will turn out easily.


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