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Antique Gas Engine Discussion

Fuel, check valve problems


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  #1  
Old 03-25-2007, 06:40 PM
Dustin D Ehli Dustin D Ehli is offline
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Default Fuel, check valve problems

Hi all, on Saturday i tried to run my Fairbanks Z for the first time on the fuel tank, I have a new line and check valve from hit and miss. i cannot blow throught the check valve and i put gas in it and it is not leaking back but engine won't run correctly, It will fire a few times then it runs out of fuel and has to intake 3 or 4 times before it will fire again. Its runnin like a hit and miss and i don't like it. Is it possible that the ball is too heavy and then it has to intake a few times to lift it and get gas to fire. i was thinking it is too heavy and one intake stroke is not enought to lift it off of the seat and get gas.
Could i replace the steel ball with a rubber one or something that will lift easier???????
I am getting sick of filling the starting chamber and would appricate all comments on getting my engine running correctly off of the fuel tank
Thanks
Dustin
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Old 03-25-2007, 07:37 PM
Bill Sherlock Bill Sherlock is offline
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Default Re: Fuel, check valve problems

Dustin,

Is your fuel tank vented? Maybe the vent hole where ever it's located is plugged? Just a thought.

Bill
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  #3  
Old 03-25-2007, 07:40 PM
Dave T
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Default Re: Fuel, check valve problems

Hey Dustin
I have a 3hp FBM Z and I tried to run it last November and it would not run on the fuel tank, so I put it away.
Last week I hauled it outside and took the fuel line off the mixer and check valve out of the tank, the check valve was ok .
When I went to reconnect the line at the mixer I noticed the gasket was torn, so I made up a nice new one out of thicker material.
Bolted the line back to the mixer, put gas in the start chamber, got her running then switched over to the fuel tank and it ran for 40 minutes.
Hope this helps
Dave
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Old 03-25-2007, 08:30 PM
Donnie Devore Sr. Donnie Devore Sr. is offline
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Default Re: Fuel, check valve problems

dustin, your intake valve spring may be to strong to pull from the tank.weaken the intake tension however you need to by replacing the spring with a weaker one or by moving the carter key hold farther out. this will let more fuel in on each intake stroke. let us know how you come out, donnie
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  #5  
Old 03-25-2007, 08:54 PM
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Junkologist Junkologist is offline
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Default Re: Fuel, check valve problems

Dustin,
Make sure the governor isn't hunting and shutting down the throttle when the engine is missing. A governor that won't settle down will make an engine run the way you describe. Does it run smooth on the starting chamber?
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  #6  
Old 03-25-2007, 10:03 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Fuel, check valve problems

Be sure the spring on the air check valve is strong enough, this valve acts like a choke when working correctly. It's harder to pull fuel from the tank than the carb bowl.
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Old 03-26-2007, 08:43 AM
Dustin D Ehli Dustin D Ehli is offline
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Default Re: Fuel, check valve problems

Thanks for all the helpful hints guys, The air check valve disk and spring are brand new from hit and miss.
The governer does hunt a little bit when running on the tank and it does run smooth on the starting chamber.
Is there suppost to be a gasket between the carb and the fuel valve seat???
Neither of my FBM engines has one there and the other one runs perfect.
The tank is vented.
Im not going home until easter so i won't be able to try these wonderful hints until then but keep them coming.
Thanks
Dustin
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Old 03-26-2007, 10:15 AM
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Elden DuRand Elden DuRand is offline
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Default Re: Fuel, check valve problems

Dustin:

You gave a good hint as to the cause of the starving problem when you mentioned that your Z runs fine on the starting bowl. On the face of it, you have eliminated the intake valve spring, gaskets, air choke, etc.

The only fly in that ointment is that the fuel has to be drawn from a lower level when running off the tank. Since the engine has to draw the fuel from a lower level, a small air leak could make your engine do like it does.

How far below the engine is the fuel tank? If it's at the same height as usual for a Z, you can rule that out.

That leaves only a few things to ponder. Remove the tank needle and seat and make sure there is no junk in it or the fuel line and no leaks. Although it has been almost ruled out, you might want to make a new washer shaped paper gasket for the tank needle where it fits into the mixer. If that doesn't do it, check to make sure the throttle shaft isn't way loose.

An air leak anywhere could cause the problem. It could be from a warped flange, loose bolt or just about anything.

Have you tried using your hand to partially choke the engine to see if it will straighten out with a -little- more choke. If so, add a couple of washers to tighten the spring a little and see if you can get it to run equally well on both fuel sources. The spring choke spring tension can make a notable difference in running, especially between slow and fast speeds without having to adjust the needle valve.

Hope this helped.

Take care - Elden
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Old 03-26-2007, 10:37 AM
Dustin D Ehli Dustin D Ehli is offline
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Default Re: Fuel, check valve problems

Thanks Elden, yes i tried to choke the intake with no success. the fuel tank is in the subbase under the engine so it is probably a 6 inch lift up to the mixer vs a vertually straight shot from the starting chamber.
I will try a gasket around it and try to tighten up the spring on the carb compensating plate.
Again i ask, is it possible that the ball is too heavy in the checkvalve so it takes a few intake strokes to lift enough fuel to fire????
Thanks again to all
Dustin
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  #10  
Old 03-26-2007, 10:43 AM
Dustin D Ehli Dustin D Ehli is offline
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Default Re: Fuel, check valve problems

How far should the carb compensating disk be pulled in on the intake stroke?? Mine sometimes goes in almost an inch. Is this way too much? maybe i need to tighten up this to create more vacum to draw the fuel up better??
Just Ideas and like i said, i don't get to try all these great ideas until easter weekend.
Dustin
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Old 03-26-2007, 10:48 AM
KidDynamo KidDynamo is offline
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Default Re: Fuel, check valve problems

An easy thing to try might be to fill the starting chamber with fuel, but leave the starting needle closed and try to run it from the main fuel tank.

If the engine then runs better from the main fuel tank, you may find a problem with the starting side fuel assembly and that an empty starting bowl allows an air leak into the main fuel system.

Perhaps this simple test could shed some light.........
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Old 03-26-2007, 10:51 AM
Dustin D Ehli Dustin D Ehli is offline
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Default Re: Fuel, check valve problems

The starting chamber was filled when i was jacking around with it but i can try it again
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Old 03-26-2007, 11:17 AM
Patrick McNallen Patrick McNallen is offline
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Default Re: Fuel, check valve problems

The check ball is probably not your problem. Dirt, or any minor air leak, or a need to adjust the intake valve or carb disc spring is more likely. Don't overlook the possibility of some kind of ignition problem. What are you using for fuel? Pump gas is a poor fuel for old engines. The best fuel currently available is "camp gas". If you insist on using the foul, stinking, alcohol-adulterated pump gas, make sure that it is absolutely fresh. If the gasoline in your tank is even a few weeks old, get it all out of there and put in some FRESH gas. If you put the engine away for even a month, remove ALL of the pump gas from the entire fuel system.
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  #14  
Old 03-26-2007, 06:34 PM
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Bill Geyer Bill Geyer is offline
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Default Re: Fuel, check valve problems

Dustin, regarding the ball in the fuel line check valve, the ones I work on at the light plant have a very light coil spring to ensure the ball returns to the seat. One time I had the problem you are having and the line was cracked where it is soldered to the mixture adjustment part that is held into the mixer by the 1/4 inch bolt. It didn't have a gasket. The crack was almost impossible to see.
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Old 03-26-2007, 07:20 PM
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Elden DuRand Elden DuRand is offline
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Default Re: Fuel, check valve problems

Quote:
Originally Posted by Dustin D Ehli View Post
Thanks Elden, yes i tried to choke the intake with no success. the fuel tank is in the subbase under the engine so it is probably a 6 inch lift up to the mixer vs a vertually straight shot from the starting chamber.
I will try a gasket around it and try to tighten up the spring on the carb compensating plate.
Again i ask, is it possible that the ball is too heavy in the checkvalve so it takes a few intake strokes to lift enough fuel to fire????
Thanks again to all
Dustin
Dustin:

Yes, the check ball -could- be too heavy. Most of them are around 3/16". Most of the time, the weight of the check ball has little or nothing to do with the running of the engine.

In a later post you said that the compensating choke plate moves about an inch. I think this is much too far, even under full throttle. After trying everything else, try adding tension to the spring.

Take care - Elden
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Old 03-26-2007, 09:37 PM
Patrick McNallen Patrick McNallen is offline
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Default Re: Fuel, check valve problems

Isn't it normal for the plate in the FB carb to make a buzzing or rattling noise on the intake stroke when cranking the engine?
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Old 03-26-2007, 10:32 PM
OldironJeff OldironJeff is offline
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Default Re: Fuel, check valve problems

Dustin,I once bought a check valve and tube from Hit&Miss and it would'nt
draw fuel.I took it of and checking I noticed a hunk of solder blocking the tube I heated it with a torch "removed of course"and it cleared.
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  #18  
Old 03-27-2007, 02:29 AM
eddie bedwell eddie bedwell is offline
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Default Re: Fuel, check valve problems

Hi Dustin,
my 2 cents worth,
had an engine once and it had a similar problem, found that the check ball was actually too big in diameter. This effectively blocked the fuel passage in the check valve body as it was a neat fit in the bore of same. Put in a lesser dia. ball and hey presto!, the fuel could then get past the ball.
Regards Eddie B.
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Old 03-27-2007, 08:41 AM
Dustin D Ehli Dustin D Ehli is offline
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Default Re: Fuel, check valve problems

THANKS THANKS guys, i have already made sure the ball does not seal on the upstroke so the gas can get past it.
One thing i forgot to mention is that when it is running like i explained, the needle valve does nothing to adjust how it runs, it won't flood out even if i have the valve almost all the way out..
Dustin
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Old 03-27-2007, 10:01 AM
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Elden DuRand Elden DuRand is offline
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Default Re: Fuel, check valve problems

Quote:
Originally Posted by Dustin D Ehli View Post
THANKS THANKS guys, i have already made sure the ball does not seal on the upstroke so the gas can get past it.
One thing i forgot to mention is that when it is running like i explained, the needle valve does nothing to adjust how it runs, it won't flood out even if i have the valve almost all the way out..
Dustin
Dustin:

That leads me to believe that you have a blocked fuel line or jet.

Take care - Elden
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