[screwdriver]

I have a 420 with the Onan B48G engine. When the tractor sits for a few days it will not start. It does not seem to be getting fuel. I thought maybe the fuel was draining back into the tank so I tried closing the fuel shut off but that didn't help It has a new carburetor so I don't think I have a problem with it. I can try to crank until it should have time to pump fuel from the tank, still nothing.. Pour a little fuel in the carb and it fires right up A couple times of doing that and it will continue to run just fine
My thought is it is draining out of the bowl but where is it going, not in the oil and I don't see any leaks. What is happening and what can I do to fix it Would a primer ball fix the problem
Thanks Jerrel

 

[shadetree]

Why not install an electric fuel pump?

 

[screwdriver]

That would be one way of solving the problem but I would like to fix the problem. I don't think John Deere meant for us to install a primer bulb or electric pump when these tractors got hard to start
Thanks Jerrel

 

[knottyrope]

fuel pump might be worn a lil bit so it wont make a check seal. Also in the tank is a check valve too. if the shutoff leaks a lil it too can affect it as well. or install a bulb to prime it

 

[tomd999]

Hiya,

Since you describe sounds like the float bowl is empty after a couple days, the fuel is going somewhere. Either it's evaporating into the air through the bowl vent or it's leaking out either via the idle circuit or a porous casting. Since 2 days is a very short time for roughly 4 oz of fuel to evaporate through a 1/4" vent opening, I would say it's draining out. Check the throttle plate and shaft ends after it's shut off for wetness. Look on the engine under the bowl for a clean spot where fuel has been dripping. Ethanol will corrode the zinc casting and eventually make a small hole at the lowest point. The idle circuit also has an air bleed that keeps it from siphoning the fuel out of the bowl as the circuit outlet is below the fuel level in the bowl. If that bleed (normally found in the top casting) is blocked, the fuel would go into the engine when it's off.

Tom

 

[screwdriver]

Thanks Tom for your ideas I think if the fuel is draining back into the tank there should be enough fuel in the bowl to crank and run a few seconds. In this case it may hit once or twice. I have checked the oil but do not detect any fuel, can fuel drain from the bowl into the engine or is the carburetor designed so that can't happen Probably will be next week before I get a chance to work on it again
Thanks Jerrel

 

[knottyrope]

heat can boil off the fuel in the carb too

 

[tomd999]

Knotty,

Although heatsoak does evaporate fuel to an extent, (part of the reason the Onan's are hard to start hot after a few minutes, same with the Mopar's from the 70's) I don't think that the entire bowl contents would go away in the time it takes the engine to cool off. For example the Carter 2bbl on a 318 has about the same amount of fuel in the bowl and that sits on top of a 500lb lump of cast iron, it doesn't cook off the fuel and that takes hours to cool off compared to the Onan.

I think the issue here is the fuel is draining out either via the idle circuit into the intake or a pin hole/leak in the bowl casting.

Now that I said all that, I'll throw out another possibility, the float level is set way too low and because of that, there is hardly any fuel in the bowl and the fuel pump is delivering just enough fuel to keep the engine running. As soon as the engine is shut off, the little bit of fuel in the bowl does evaporate out because there is only a small amount in the bowl.

There, I think I contradicted myself quite well in that post.....

Tom

 

[screwdriver]

Finally got around to working on my 420 again as it turns out it was draining fuel back into the tank. I have started shutting the fuel off and the problem seems to be solved I now have a new problem which I will cover on another post
Thanks Jerrel

 

[gzec]

If your fuel line is too short or pulled down away from the carb, gravity might be sucking the gas out. Have the fuel line slightly elevated after the fuel pump and before the carb. This is where I have a fuel filter. Just needs to be ever so slightly higher than the carb bowl.

 

[motorcarm19]

I have a new 430, well new to me. When I got it I knew the mower deck clutch didn't work, an after finding that the problem was at the clutch, I removed it from the machine. I cant get it to the .018 air gap. When I ajust close to the gap the compression ring is so tight the outer ring wont turn, and I am still now where close to .018. Here is what I do know. When I place a straight edge across the shaft bearing and gap the difference between it and the contact area I get the number .110 and when with the clutch parts together with out springs and nuts I come up with a gap of .075. Both numbers seam large to me??? What have I done?, what did the PO do to me? and how do I fix this ? With out spending a lot of money. The field coil does work , but it could be week. How does one test this, or is this one of those all or nothing cases. Brian

 

[motorcarm19]

Boy did I go the wrong way