Which Carb are you working with??

 

The carb is the Motorcraft 2100 series (2150 I think). I rebuilt it during the time I was doing everything else, and the kit included a new power valve among other things. The fuel filter is new, but it is cased in metal so I can't see inside.

I tried sucking some gasoline out of my tank a couple of days ago using a hand fuel pump, but I couldn't get the probe down in there far enough. I need a longer hose.

I have ordered new gaskets for the carb to spacer and spacer to manifold. During the rebuild I cut my own gaskets out of the sheet material they sell at the parts mart. Still, I can't imagine how so much liquid fuel could leak out at those.


Anyway, until I get my starter rebuilt, I'm at a sort of stand-still for this carb problem. It's always an Alice in Woderland story... the rabbit hole of repair always goes deeper!

Thanks for the suggestions. I'll buy some new vacuum lines and check the vacuum.

- james

 

Did you completely disassemble and soak the carb when you had it off? What I'm getting at is this... If the float bowl is empty and you're getting fuel on the manifold in the quantity you have described I'd start by checking for a crack in the base or bowl of the carb. The 2100 series is a pretty simple carb so I doubt that anything was left out, like a jet or the gsket on the power valve... Good luck, I'd like to know what you find when you do.

 

Or do you have your idle screws in too far? It sounds like the idle part of the carb is not working.

 

Yep, kinda sounds like it's leaking if it's empty. And if it were, that would cause the problems you describe. At low rpm, it's flooding out I bet. The sooty plugs indicate this. I'd pull the carb off, and fill the bowl with gas. Then let it sit for a while on a piece of newspaper, glass or whatever. See if it starts to drip. Cracks in the carb itself can do this. Also, the power valve will cause that if it's leaking. Naturally, check the needle and seat while you are in there. I had this problem, and it was a tiny leak in the power valve diaphram. It would drip, drip, drip. With each drip, my idle would go rich. So it would hunt back and forth...Almost mimicked a vacuum leak..BTW, the black looking gas might just be discolored due to seeping through a gasket or something. I wouldn't overly worry about that if the gas elsewhere looks clean. If the gas is dirty, there will be a layer of dirt/rust at the bottom of the bowl. It's usually fine particles on these old trucks.
MK

 

Here is the follow-up, and I'd like to thank all you guys for the excellent suggestions.

Over the weekend I pulled the carb off, placed it over a catch-basin, and filled the bowl with gasoline. Immediately fuel started dripping out the bottom! Half the fuel leaked out within a minute, before the leak slowed down.

So after looking around and breathing gas fumes for 20 minutes, I found it! The new gasket for the venturi assembly mount was not cut right! (this is the gasket that came in the carb kit). One of the holes in it was barely too small, so that the venturi assembly pinched it and could not seat all the way. This left a tiny gap where fuel spilled out when the bowl was full.

So I trimmed the gasket with an Xacto and reinstalled it. That solved that problem.

However, when I tried the experiment again, I still had a drip (albeit slower). I discovered that I had not tightened the power valve down hard enough, allowing fuel to leak right out the bottom. That explained the dirt and grime in the fuel puddles I'd seen, since there was still a little leftover grease and gunk down there.

I tightened the power valve down good, reinstalled everything else, and now... (dramatic music) No leaks!

So it was true that the engine was flooding every time I tried to slow it down. Just too much fuel spilling in there.

Again, thank you all.

Of course, I won't know for "sure" that this works until I get a new starter, since mine is fried.

cheers,

james