Fuel check valve

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Vietti

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I've built a few hit and miss engines and because the carb was pretty low compared to the fuel tank never needed or used a check valve.

My current engine is a model of the Fairbanks Morse model N. The carb is in the head and is 3-4 inches vertically above the fuel tank. It needs a check valve. I've made the one according to the plan but it occasionally leaks back a little and the engine has to hit a few times to get fuel back up on the needle, I can see the fuel drop thru the clear fuel tubing.

It is the classic one way valve with a 1/8" ss ball sitting on a seat with a hole. Tried truing up the seat and a bigger, heavier ball. Have struck the ball with a drift to seat it and still the fuel sometimes drains back. It doesn't help that the engine only fires every 4 seconds or so. I've gone so far as to use a viton tipped needle valve in the housing instead of a ball but no joy.

Any ideas to fix the situation would be appreciated!
 

Dragondark

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Vietti I use something similar in my mason jar bubble carbs. I've found that if there is *anything* remotely able to get jammed in between the ball and the seat it will. I still can't figure out how half of the stuff that gets in the seat of the check ball does it since it's only sucking vapor and not liquid fuel.

I second Green on the spring, very light pressure to assist gravity and not fight the ball lifting.
 
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After hitting the steel ball did you replace it, or use the same ball in the valve? Perhaps the ball has been damaged sufficiently to prevent a perfect seal.
Have you thought of using a Viton ball? The rubbery material will slightly deform and should make a good (better?) seal.
Viton balls are frequently used by the steam engine boys in their check valves for exactly that reason.

Dave
The Emerald Isle
 

minh-thanh

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A little bit of my experience with ball valves: Make it really tight, and if it's really tight you just need a spring with very little force to hold the ball in the closed position or add another ball to hold it with weight
 

Jasonb

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I've done a couple of engines with foot valves, just a small parted off circular disc with a small flat filed on one edge and that drops down onto a flat seat and is lifted by the carbs suction. The R&V horizontal that I did has one and lifts the fuel about 3"

The PM Research NR valve that I bought for the Ball hopper Monitor also worked OK as well as looking the part.
 

rickhann

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I had the same problem with my Upshur engine. I had heard of others using capillary action to restrict the flow. The fuel mixer has a .031" hole that is further restricted by the needle valve. I simply placed an additional restrictor .031" in the fuel line at the bottom of the fuel tank. My thinking was that during operation, the fuel in the line would not be able to drain back into the fuel tank fast enough to starve the engine. Worked great. To start it, I just choke the mixer to get fuel into the line. Once the engine starts, fuel draining back is not a problem. No moving parts. Rick
 

Basil

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I’ve had good luck with this setup in a few different applications. 👍
 

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chrsbrbnk

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In a sortof related problem is the check vlv on steam engine oilers seem to be really prone to getting debris in them. I'd like to see some really decent check vlv designs for different fluids and pressures.
 

Vietti

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I don't usually gush but---I tried Basil's fix of two balls , one large one quite small and it seems to be working great! No back flow, even when the engine sits for a while there is very little back flow. The engine now hits first time, every time. I wish all problems were so easy to fix!
 

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