Marvel Schebler mystery

I recently purchased a '47 Ford 8n and am trying to get it up and running.
Here is my first dilemma. I rebuilt the Marvel Schebler using one of the major kits with the new jets,needles,shafts etc. I reused the brass float because it was perfect. I hooked up all the linkages for accelerator, choke and governor, turned on the gas. It fired right up but at full speed. I immediately shut the engine off and checked all my initial needle settings and fired it up again with the same results. This time, however, gas began pouring out of the air intake. Immediately I thought " stuck float" so after tapping on the carb, to no avail, I pulled the carb off again and opened it up. The Float Was Sucked Flat!
I do have another carburetor with a good float that I just installed. What would cause this to happen? I can't imagine that there would be that much suction in the carburetor bowl as to cause the float to collapse. Any ideas before I put the carb back on?

Choke stuck closed?

Rod from governor to carburetor free to operate?

Broken governor linkage inside the front cover?

The spring speeds it up, the governor weights slow it down.

wrench rancher.........carbies run on VACUUM. yer description of collaped float is consistant with OVER-PRESSURE. Tink about it.......the amazed Dell

(quoted from post at 09:11:37 05/27/17) wrench rancher.........carbies run on VACUUM. yer description of collaped float is consistant with OVER-PRESSURE. Tink about it.......the amazed Dell

Click to expand...

Dell,
I tink I tought about that, but where would the over pressure come from in a tired old engine with low to mediocre compression?

Amazed Dell ..... I'm amazed that you didn't explain your post further. Sounds like brain surgery to me but I'm sure you can clarify things for those of us mortals who are stumped.

A plugged bowl vent would cause the fuel running issue. It sets up a siphon and there is no air to break the flow. A stuck float will cause this as
well. I have never seen a float collapsed before, though. That is a new one on me.
Let us know what you find.

Aaron

Did you at any time use air pressure on the carburetor after it was re-assembled. Only pressure would cause a float to
implode. There is no way to get a vacuum inside the float tanks. Suction would cause it to expand, not collapse!

Massive amounts of fuel to the engine without an increase in air to it also should not allow the engine to run full speed. The last one I had run full speed, even with the carb linkage held to idle, was caused by the heads of two screws that hold the throttle plate to the shaft being broken off and the throttle plate was stuck vertical in the throat.
Collapsed floats are usually caused by water in the carb bowl being frozen.

Bingo!

My son in law collapsed the float in his Ford trying to blow out the fuel line by putting air on the carburetor drain to blow back to the tank. I think the air flow lifted the needle valve and sealed it.

I had a similar problem after a guy rebuilt his marvel. In his
case, the new brass piece the needle jet seats in had rust
under it and the fuel leaked around the brass piece he put.

Had a heck of a time getting it to stop.

One person on YT suggested using a small glass container you
can see through as the carb bowl. That way you can see when the
float is up and where the leak is coming from.

Good luck.
geo

Is the new throttle shaft exactly the same as the old one? Pay close attention to the relation of the lever to the throttle plate. I have seen them not right and the throttle will not close properly.

Sounds like you have 2 separate problems.

The runaway engine is caused from improper throttle linkage adjustment/installation,or a failed governor. This has nothing to do with the mixture adjustments.

With the engine off, have an assistant move the throttle lever through the motions while you watch the throttle shaft of the carb move. You should see the carb shaft move against the idle stop when the lever is set to idle, then see the carb shaft move to the wide open position when moved to the fast position.

The governor works by pushing the throttle shut as the RPM come up. The governor spring opens the throttle, the spinning governor weights overcome the spring and push it closed.

Once you get it going through the motions, you should be able to see it work as the throttle speed lever is moved from slow to fast. If it still won't work, I can give more detailed adjustment procedures but it gets lengthy.

Now, for the collapsed float, I have never seen that happen, but as others have said, it takes external pressure to collapse it.

That can be caused from applying air pressure to the carb bowl through the vent tube (most likely cause), or possibly a very powerful backfire with the choke closed, (plausible) or maybe the engine kicking back and running backward with the choke closed, (plausible but not likely).

Rancher.......stuck intake valve. Pump pressure out into the carbie.......Dell

I ran into this problem on a NAA,it would not slow down to where it should idle. I put old throtle shaft back in and everything is fine.

Thanks everyone, for all your useful suggestions.

I seem to remember that I did take the air hose to the carb intake so----collapsed float mystery is solved.

I replaced the float and put the carb back on with the same flooding issue. However, I pulled it apart again and adjusted the float level, but now I think I went too far because it runs just about long enough to use the fuel in the bowl before it quits. So I will have to pull it again and find a happy medium.

I backed the idle adjust screw all the way out and made sure the choke and throttle and governor linkages were back against the stops and fired it up again. This time it ran a little fast, but not excessive, so I was able to adjust the carb screws to idle it down. When I gave it some throttle however it died, possibly at the point where the gas was used up in the bowl. I will go back into the the carb and re-adjust the float after the Memorial Day Holiday then report back.

Thanks WR

Thanks Steve.
I might take you up on the offer for the governor adjustment after I get the carb figured out.

Wrench Rancher

(reply to post at 10:11:28 05/27/17)

Click to expand...

Absolutely right , Roger!
My air hose got loose and attacked the carb intake. Must be a conspiracy.....when tools attack. javascript:emoticon(':wink:')

Just finished my Allis B and ran into some simular Marvel carb problems also. I also cleaned extensivly and used a high end rebuild kit. Kept flooding. Figured out it was the new needle valve with a rubber tip and a clip. Replaced it back with the old needle valve and no clip. No problem. My only remaining problem is it wants to run a lot of choke. Hope this helps.

(quoted from post at 08:11:28 05/27/17) Did you at any time use air pressure on the carburetor after it was re-assembled. Only pressure would cause a float to
implode. There is no way to get a vacuum inside the float tanks. Suction would cause it to expand, not collapse!

Click to expand...

Air pressure at the fuel inlet will collapse a brass float in less than a heartbeat!