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Farmall B-carb

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Dave H (MI)

09-12-2007 10:12:33

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Still trying to get my mind around a few things so I can solve my starting issues. Tractor was inside last night so I thought my starting troubles would be at an end but they are not. Hit the starter this AM and, once again, it cranked and cranked but no sign of any ignition. Then a pop and some white smoke, followed by a increasing pops and eventually a start with lots of white smoke. Liquid sprays out from around the base of the muffler onto the hood. I ran a finger thru it and it is gas, not water. It dries quick so I don't think there is water in it anymore....but why would gas not fire in the presence of spark unless maybe, two much gas?

My own logic (and others) tells me to check to see if there is spark but of course there is because it runs. I just timed the engine a while back and got it starting great, rebuilt the carb and it starts like described. Why would there be no spark for 20 seconds and then suddenly spark? This is the puzzle I cannot get around.

OR...it was mentioned the float was set too high. Is it possible that this puts too much gas in the mix and overwhelms the spark making it not fire? Then one happens to catch and the engine slowly evens out while blowing the excess gas (the liquid) and vapors (the smoke) out the exhaust?

Can't work on it today but I am thinking about it a lot. Either of those two ideas make any sense?
The spark idea seems like a long shot to me but the presence of liquid gas in the exhaust seems to me like I may be drowning my spark. Am I starting to make sense?

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Dave H (MI)

09-12-2007 18:42:14

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

Thanks all so much for all the help. I will pick up a clear hose and fitting when I am out tomorrow and start doing some investigating. I will also check out the float. It was taking in gas when I did the rebuild but possibly I damaged it and it now is gas soaked. Anyhow, I will check and get back to you with what I find. Thanks again!

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Brownie450

09-12-2007 17:16:18

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

Is the float dry[ as in no gas inside of it]?

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Owen Aaland

09-12-2007 15:55:20

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

One other way you could be getting too much fuel into the intake is if the gasket is leaking on the main metering tube or the tube itself is damaged. If the gasket is leaking it will allow fuel to get in below the venturi even if the float level is correct.

To check the float level while the carb is assembled on the tractor, get a hose barb fitting that will screw into the hole for the drain plug. (I think it is 1/8 inch NPT) Use a piece of clear hose to connect to the fitting and run it up along the side of the carb. When you turn on the fuel you should see it rise up to the same level as it is inside the carb. I do not know what the correct height should be but it must be below the bottom hole in the metering tube.

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teddy52food

09-12-2007 11:51:10

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

Shut the gas valve off at the sediment bulb when you stop it. Let it set overnight. Then try it with the gas still off. It should start ,then turn it on. I think your needle & seat is leaking and loading up the air cleaner.

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Dave H (MI)

09-12-2007 14:16:54

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Re: Farmall B-carb in reply to teddy52food, 09-12-2007 11:51:10

Teddy, take a look at what I wrote to Jim below and let me know if you can add more. I wanted to tell you that the gas is shutoff every time I stop the tractor. USUALLY, I forget to turn it back on before I try to start it. Tractor has never started with the gas line shut off and I have cranked her pretty good before the light came on and I turned on the gas.

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teddy52food

09-12-2007 18:18:47

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 14:16:54

Have you tryed using the choke with the gas shut off? It may need a full choke for one or two compressions with the switch off. then open the choke, turn on the ign & hit the starter. It should pop right off. Did you check the float & make sure there is no gas in it? If the float is heavy with gas ,the fuel level will be too high before the needle can shut it off. Take the drain plug out of the bottom and put a barb & clear line on. Loop the line upwards, turn on the gas & see where it levels out. If it slowly rises ,the needle is leaking. Keep us posted OK?

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Janicholson

09-12-2007 11:45:21

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

Dave have you been shutting off the fuel at the tank when it is stopped. I indicated the necessity of this in an earlier post. The needle and seat in the float bowl are not seating perfectly and allowing about 20 drops of fuel to leak past in an hour. This fills up the float bowl and starts leaking fuel into the venturi area. When you start it this fuel is sucked into the engine flooding it dramatically. You are getting spark, it is just submerged in liquid gasoline. As you crank it the fuel eventually blows out the stack, and it will begin to chug to life. Very hard on rings, and not good for oil dilution and other parts.
The fix will be a combination of a new needle and seat, Or using fine auto body buffing compound and spending some time polishing the needle into the seat to clean it up (3 or 4 minutes of twisting it into the seat by hand should do the trick, AND!!!!! !! shutting off the fuel when stopped for more than 10 minutes.
This is the real issue with starting, not the idle issue Best of luck, JimN

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Dave H (MI)

09-12-2007 14:14:13

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Re: Farmall B-carb in reply to Janicholson, 09-12-2007 11:45:21

Hi Jim, I understand what you are saying BUT I have been religiously following the instruction regarding shutting off the gas. I do it every time I am done with the tractor. Not that I am the greatest about following instructions, but when you combine it with $3.20 gas dripping out my motivation level spikes. The gas IS shut off. I turn it on immediately before I try starting it and get this result. The needle AND the seat are brand new and newly installed. Does this or would this change anything you said above or is the gas still dripping sufficiently to flood the venturi area? Trying to word this carefully because I am not arguing or challenging, just want to make sure you understand the facts. Given that I am turning the gas on immediately before I try a start, is the float the more likely culprit or no? Thanks for your patience! I am learning a ton from all your input.

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Janicholson

09-12-2007 18:51:08

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 14:14:13

No grief here!!
There is a distinct possibility that the fuel is not actually shutting off to the last drop. Many valves have been found to be not seating, thus the drops per hour thing is still relevant. The shutoff valve (is supposed to) shut the fuel before the sediment bowl. Thus if the glass bowl is removed, the leaking valve will be detected. The needle and seat often leak in a rebuild (they haven't "mated" yet, though living together. I believe this is your issue. If you have left it for some time this evening, pull the rubber intake hose off if the inlet and see if there is gas in there running l;oose. If so, I am correct. Unless your carb is producing its own refined petroleum. Best of luck with this, I do not think there are many stones left to turn over in the fuel system. Jim

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RustyFarmall

09-12-2007 11:19:22

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Re: Farmall B-carb in reply to Dave H (MI), 09-12-2007 10:12:33

An overly rich fuel mix will definately kill the spark. I think you need to open up that carb again.

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Dave H (MI)

09-12-2007 11:30:19

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Re: Farmall B-carb in reply to RustyFarmall, 09-12-2007 11:19:22

Yup...I was just reading the part in the manual about float operation and I think there is something there that needs a look.

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