air bubbles in settling bulb

Oscar Thompson · Jul 17, 2008

I have a 1939 B Allis with a belly mower which I have used for many years. Lately it doesn't run very long at a time (1/2 hour maybe) then sputters a little and quits. Each time that I use this tractor I notice that there is air bubbles accumulating in the settling bulb. Then the engine seems to "run out of gas." Any answers as to why air bubbles should accumulate in that bulb?

Lanse · Jul 17, 2008

could there be an air leak in there somewhere (hose, carb/manifold, etc). just running ideas here.

Oscar Thompson · Jul 17, 2008

I've just replaced the manifold, cleaned the carb, replaced the copperline from bulb to carb with a rubber hose, switched from ethanol based fuel to regular gas, and #$#$#..it still bubbles up in the settling bulb.

Lanse · Jul 17, 2008

still possible. Im assuming that if you replaced all that you would have used new gaskets, and replaced the sediment bowl gasket, or no??

Oscar Thompson · Jul 17, 2008

Yes, and if the settling bulb gasket is not tight it'll leak gas OUT, not air IN. ???

Drill · Jul 17, 2008

If you have air in the bulb you have more gas going out than coming in, check line from bulb to tank, line or valve coming out of tank, tank itself and cap for proper venting. Hope this helps.

Lanse · Jul 17, 2008

Hey, im trying to help you here!!

Like its been said, theres more going out then coming in. MAke sure the bowl opens all the way. Make sure that theres nothing blocking the drain of the gas tank. See if the bubbles dissipper when you remove the gas cap. If they do, drill a tiny hole in the gas cap.

Dan-IA · Jul 17, 2008

air leak / gas leak in sediment bowl gasket.

in a pinch you can make one out of the cardboard box from the last pair of shoes you bought at walmart for $20. BTDT.

Dan-IA · Jul 17, 2008

air leak / gas leak in sediment bowl gasket.

in a pinch you can make one out of the cardboard box from the last pair of shoes you bought at walmart for $20. BTDT.

old · Jul 17, 2008

Well first off its called a sediment bowl but any how sounds like the fuel line is to close to the engine or manifold and that is causing the gas to boil in the line and that will then cause bubbles in the sediment bowl. Also rubber fuel line is fine on cars and trucks but not good on tractors because of all the stuff a tractor goes through like tree limbs etc and that can/will pull that line off and can/does cause fires
Hobby farm

Oscar Thompson · Jul 17, 2008

Good thoughts. So I rerouted the gas line out away from the block, outside of the air cleaner, and it did no good. And by switching to a rubber fuel line -- yes, it does create a fire hazzard. Thanks. But it is something somebody suggested - just to try. Anyway, I am still looking to solve my ongoing problem.
When I disconnect the line from the carburetor the gas runs a nice solid flow through the 1/4 inch line. NO problem with flow from the gas tank.

Oscar Thompson · Jul 17, 2008

Yes, thanks for the reply.
I've even removed the fuel tank cap temporarily while running and it makes no difference. I've cleaned the mesh screen in the sediment bowl so it's in good shape. AND >>>>>>>>>>......????

rustyfarmall · Jul 17, 2008

Take a good look into the fuel tank. You've either got a foreign object floating around in there, or you have developed a rust problem. Possibly also the screen in the top of the sediment bowl is plugged up. How long has it been since you removed the glass bowl, and the screen, and gave them a thorough cleaning?

old · Jul 17, 2008

Start it up with the gas cap off and see if that helps or hurts. The tank vent could be clogged up and causing a vacuum in the tank. Oh you don't by chance have an in-line fuel filter on it do you?????????

Sid · Jul 17, 2008

What Old said.

Lanse · Jul 17, 2008

I think its time to move to ignition. Sounds like fuel isnt it. I just learned what a point was, so i cant help you here, but old will. Good luck to you.

Oscar Thompson · Jul 17, 2008

I use this tractor every week doing the mowing. I even drained the tank, through the fuel line, to watch the flow. And it drained completely at a steady flow. The sediment bowl and screen have been off many times recently, trying to figure out where the bubbles are coming from. They accumulate in the top of the sediment bowl while the engine is running and then it acts like not enough fuel is getting to the carb. Still stumped and feeling stupid.....

Oscar Thompson · Jul 17, 2008

No inline filter. Gas flows easily to the carb. Thanks for the thoughts.

Oscar Thompson · Jul 17, 2008

Thanks, been there -- done that. This '39 B has a magneto and I even replaced it with a rebuilt one. NO CHANGE.

Handyman · Jul 17, 2008

I have a Allis C that does that on occasion, take the fuel bowl off and look at where the fuel enters the bowl you will see the end of a tube with the end blocked off and a notch on each side of the plug, take a small stiff wire and poke it through there and you may find some rust or other debris coming out as you work the wire back and forth. this usually cures the problem for me.

Lanse · Jul 17, 2008

And i too am restoring a 1939 B. Not as fast as you are though

I dont know about mags at all. Or distributors. I have 2, one worked when i got it and one is being rebuilt. I would test for spark on that thing though. I've never done it ON the tractor, but on a mower, all you do is remove the plug HOLD THE CERAMIC PART OF THE PLUG ONLY and hold it to the head and have someone spin the enigne the same, and im guessing the Bs are the same. Be very, very careful. Dont do it near ANY gas, and DO NOT touch anything metal or else.

And dont listen to me. Wait for someone who knows what theyre doing to jump in here.

Oscar Thompson · Jul 17, 2008

Thanks, I'll check that out tomorrow !! That's one item that I haven't checked yet.

Oscar Thompson · Jul 17, 2008

Thanks, and have fun with the restoration. What year is your B?

DickL · Jul 17, 2008

When a tractor will run for a 1/2 hour before having a fuel flow problem the first place I look is the gas cap. It takes about that long to pull a vacuum on the tank enough to stop gas flow.

Oscar Thompson · Jul 17, 2008

Thanks, I've even removed the cap when it starts to do some sputtering. NO relief -- just makes me sputter some more...

Frank A · Jul 17, 2008

Just wondering,are you having any back pressure like from bad valves or timing? Don't know if it would matter just a thought.

Oscar Thompson · Jul 17, 2008

I've been wondering if this could be a possibility. It wouldn't hurt to do a valve job, I'm sure. Maybe this is the best answer yet. Thanks. And I'll recheck the timing of the mag, too.

Lanse · Jul 17, 2008

same as yours L-)

Is your 39 still orignal with the crank, mag, and no lights or starter???

dave guest · Jul 17, 2008

If it was my Cub or A, I would blow out lines and filter, bowl, all of it. Are you using more than one filter. Can be problem. Are you using in line filter? All of them won't work. How a bout stuck needle in carb, has it been apart? My Cub has been without filter for over ten years, won;t run with any I have tried.

Anonymous-0 · Jul 17, 2008

I would drain the tank and remove the sediment bowl assy look for some foreign stuff in the inlet. Dont worry about the rubber hose as ive got one tractor thats had one for a fuel line forgoing on 25 pluss yrs. It was on the tractor when i bought it and have never changed it. This tractor lived at 10,000 ft elevation for 8yrs while i had a job in COLO. It runs on ethanol and just works starts in the winter as its my snow removal tractor. Starts on 6v everytime at below zero or whenever i need it.

Janicholson · Jul 17, 2008

Find an old gas tank from a lawn mower, or other machine. Hook you rubber line to that and see if it will restart, and run. If so, junk in the tank/outlet. If it makes no difference, the rubber line may have a bad spot in it and swell shut. If that is no relief, I again suggest as others have, it might be a weak coil on the mag, getting hot, and failing to work (two can be mediocre). JimN

olddog · Jul 18, 2008

Sure they're air bubbles???
Water is heavier than gas.

El Toro · Jul 18, 2008

When it quits running pull off one of the sparkplug wires and see if it has fire to the plug. You need to do this asap before the engine cools. You may have a bad condenser or coil. Hal

Oscar Thompson · Jul 18, 2008

Yes, it is the same original '39. Thanks for the picture. It looks very familiar. I have a belly mower on mine so I use it all summer for yard mowing. Great little tractor.
I'm wondering if my carburetion problem could be coming from possibly worn intake valves allowing hot gases to escape backwards into the carburetor thus vaporizing the gas in the carburetor? I have not overhauled the engine yet. This senario has also been discussed by one of the responders last night. Otherwise I have tried just about everything that has been mentioned.
Ordinarily one pull on the crank and it's running. So it's very easy to start. Let me know how you are coming with your project. Thanks.

Oscar Thompson · Jul 18, 2008

Ya, they float in the top of the settling bowl. Then I drain the bowl, let it refill with gas and close it up tight, again and again....

Oscar Thompson · Jul 18, 2008

Thanks, I have even replaced the magneto, thinking that it may be weak, but to no avail. Still plenty of spark, anytime.

Oscar Thompson · Jul 18, 2008

Thanks for the thoughts. I have drained the tank, put on new hose from bowl to carb, cleaned the screen in the settling bowl, checked the flow through the line to carb, etc...
So what else should I check??

Oscar Thompson · Jul 18, 2008

I drained the tank, and checked the screen and bowl (many times by now) and still have a nice full flow through the line right up to the carb. I had the carb off a couple of times to clean it -- to no avail.
This '39 has a magneto and is very easy to start (one pull). Ordinarily use it all summer with the mower.

Oscar Thompson · Jul 18, 2008

I don't use an inline filter, but the flow is great right up to the carb. I had the carb off a couple of times and cleaned it, too. But????

Oscar Thompson · Jul 18, 2008

Thanks, but if the gasket was not tight then gas leaks out, not air in??
I have drained the air off that bowl numerous times, sealed it up, and within half hour there are bubbles floating in the top of that bowl again, and eventually the engine sputters and dies. UGH

Oscar Thompson · Jul 18, 2008

Thanks, I have checked, tightened, removed, cleaned, @#$#@#@#$, all to no avail. But do you suppose the gas is vaporizing and pushing backwards into the line from the carb///???

El Toro · Jul 18, 2008

You need to place your hand over the throat of the carburetor when it quits to see if there's good suction on your hand while someone cranks the engine. Hal

Waltmo · Jul 18, 2008

Check for leaks in exhaust system, may blow hot gases onto carburator. You may want to temporarlly insulate the carburator from heat with a peice of thin metal like stove pipe to keep heat away from it. Also what kind of gasket do you have between the carburator. Does it insulate it from conducting heat from other parts of the motor?
HTH WaltMo
P.S. A split rubber hose over the metal gas lines may help keep the heat off them.

bill mart · Jul 18, 2008

lot of people call them a sediment bulbs.Deere parts manuals have described them as fuel filters. bill m.

Oscar Thompson · Jul 18, 2008

My apologies for not calling it a sediment bowl.

air bubbles in settling bulb

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