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Discussion Starter · #1 ·
I thought the purpose of a Fuel Shut-Off Valve between the fuel tank and carburetor was to be able to run the carburetor dry so it doesn't gum up with bad gas.

It never occurred to me how necessary the vented gas cap is for engine operation. As soon as the shutoff valve is closed, the engine dies within 1-2 seconds. Fuel remains in the carburetor bowl as well as the fuel filter, but the engine won't run any longer because the fuel system is non-vented with the valve closed.

So maybe I have this all wrong, and the shutoff valve is intended to stop the flow of gas from the tank so the carburetor and fuel filter can be drained and serviced manually ?

By the way, is this fuel filter too big? This was all they had in stock.

 

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It doesn't need a vented cap to run only to allow the fuel to flow. I have had trouble with fuel filters like those getting the fuel through them. May be that it causes a vapor lock that stops the engine. My only suggestion is to remove the filter.
 

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Discussion Starter · #6 ·
Hmmmmm, battery, key switch ........


I'd find a smaller filter, reroute the hoses for better drainage and maybe add another petcock/valve to vent the line if you want to run it dry.
We don't use the tiller often enough to keep the battery charged. Thus, the electric start is of no benefit. That battery is the original and has been dead for 25 years. :)

Should the fuel filter be positioned vertically to drain better?
 

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Discussion Starter · #7 ·
It doesn't need a vented cap to run only to allow the fuel to flow. I have had trouble with fuel filters like those getting the fuel through them. May be that it causes a vapor lock that stops the engine. My only suggestion is to remove the filter.
Interesting. Would you recommend another type of fuel filter?

I only expect to use the tiller 1-2 times per year. With these types of filters, if fuel remains in them when winterizing the engine, will the pleated paper absorb the gas and gum up as the gas ages? If yes, maybe a different filter design is prudent with a quick disconnect of some sort?
 

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Even the smaller paper filters foil up if stored over the winter with fuel in them. Changes to an awful dirty brown color, too. I change filters before season use, usually in the spring. But this year, I've replaced 2 or 3 complete fuel systems so far, between filters, valves, and now failing fuel hoses.
With 13 machines, it seems as though all I do is maintenance.

Yup, I'd get a smaller filter for that size engine, the next time you change it out.
 

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I think that when you shut the valve off, it is like putting your finger on the end of a straw and pulling the straw out of the glass. The soda stays in the straw, and likewise the fuel stays in the line and filter.
 

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I have no proof,but I put a cut-off between tank & filter and when it quits;it takes more than a few sec.to be restarted.So my thought is that it burns what fuel is in line & filter.Also when eng.is running there's always so little gas "seen" in filter,that I can't really say it's dry when it quits,but it does act like it.
 

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Rather than for running the carburetor dry (although I have used the shutoff for that, too), I use it to keep the tank from draining if the float valve in the bowl malfunctions.

Bill
 

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The shutoff on my B&S Vanguard is the only way I can shut down the engine. Manufacturer does that to prevent gas from getting into the crankcase and diluting oil when the motor is transported. On my ATV I was also told to use the shut off when transporting for the same reason.
 

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I put shut-offs on about everything I work on anymore. And have got into the habit of shutting them off before killing the engine,,and I have never had a immediate response to shutting the gas off. Although I do not try to run the bowl empty,,they all have run fine with gas off.

I can't think of a good reason for a immediate response to shutting the gas off. It just shouldn't happen.
Only thing I can think is the float is adjusted just right to where the bowl is not completely full and any interruption in gas flow makes a difference.

The filter shouldnt matter either,,,if the bowl is full,,it should still run till it is empty,,before needing any more gas from line or filter.

No solid answer here,but makes you go Hmmmmmm????:dunno:
 

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That filter is likely designed for a fuel system on a car that uses a fuel pump--they dont always let enough fuel flow thru by gravity alone,to keep a small engine's carb filled up sufficiently,and it'll make it tend to die under a load ...they sell ones that look the same,but have larger pores in the filter so gravity alone will be sufficient to let gas go thru them OK...some use paper elements,others are sintered bronze,or a fine mesh screen instead...if you had a fuel pump that one would be fine though...

I have shut offs on most of my engines,and after I close one with the engine running,it takes several minutes for it to finally stall and run out of gas,they use up every drop in the bowl..(and if I didn't run them dry,I'd find a puddle under the carb come morning too!--I dont know how the gas can get "used up" when I'd think it should be airlocked,but somehow it still manages to either flow,or get sucked into the carb,perhaps by engine vacuum??..
 

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A fuel shutoff is quite handy in preventing hydrolocking the motor when in storage, as well as preventing the fuel from draining through the carb all over the place when you least want it to.

Hydrolocking can happen when the needle valve in the carb does not shut off the fuel flow all the way, and the fuel finds its way through the carb and into an open valve in the intake, and down into the crankcase. The crankcase eventually fills up if there was enough fuel in the tank to do the job but either way, the oil is contaminated by fuel, and the crankcase is waaay too full with the oil/ fuel mix. Sometimes the motor will crank over, sometimes not. Either way, it's not a great scenario , thus the use of a petcock or shutoff valve.. Running the motor on contaminated fuel is sure a good way to toast a motor.

If storing a unit like you have ( I do have one like it ) I just shut the fuel off , drop the bowl and drain the line too. Re-assemble, and it's good to go for the next time to run it.
 

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That one would be fine if it was mounted vertically to get the air out and let it fill up.
I had a '65 Chevy once with a 230 ci (I think) inline 6 that had a fuel filter just like that except one end was at 90 degrees. Unfortunately, I don't remember which end :(
You could just add a 90 fitting to that one.
 

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Discussion Starter · #18 ·
Thanks, everyone. I'll look for a smaller fuel filter better suited for this engine. Would everyone agree regardless of the filter used it should be mounted vertically using a couple of 90 degree elbows, or is that not as important?
 

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I don't think a smaller filter mounted horizontally will present a problem - it doesn't on mine! But look at the gas level in your picture - how much of the filter media is actually doing any filtering? Most of it is wasted. There is a nice advantage to the bigger filter - the bigger surface area means less resistance to flow as it starts to get dirty, and also it won't clog as easily. By placing the larger filter so that the entire media is wetted, you'll benefit from both of those.
 

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I don't think a smaller filter mounted horizontally will present a problem - it doesn't on mine! But look at the gas level in your picture - how much of the filter media is actually doing any filtering? Most of it is wasted. There is a nice advantage to the bigger filter - the bigger surface area means less resistance to flow as it starts to get dirty, and also it won't clog as easily. By placing the larger filter so that the entire media is wetted, you'll benefit from both of those.
I donot believe that to be any problem at all. The machine it is mounted on will shurely "shake rattle and roll" when in wok so the fuel will be splashing around lilke crazy and pass through any area it contacts with.

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