Ok so here's the run down on my bronco ii. I have been a member of another forum for quite sometime, but I cannot seem to get any feedback from anyone, and the last post other than mine was in the earlier part of this year.

1985 Bronco ii 2.8 Cologne V6, Automatic (A4LD Trans), 4X4

Air screws on carb had to be at more than 3 1/2 turns out (ridiculous I know) and the truck was still smelling rich
Also have an issue of when I step on it: meaning it downshifts and rpm's increase, I am not getting any added acceleration at the rear wheels.
Adjusted band bolts on transmission and it improved a lot, but still not like it should be.
Did a full rebuild on carb, but I still have to keep the Air screws turned way out. Checked timing, advance, everything I could think of.
I am down to thinking that the Mechanical fuel pump is pushing to much fuel which is keeping the carb rich no matter where I put the screws.
I have checked for vaccum leaks everywhere. I did pull the vaccum line off of the pump by-pass valve on my carb and it shot out fuel when I unhooked it. Float level was good when I rebuilt carb. New seat, needle, accelerator pump, enrichment valve, all new gaskets and all passageways cleared. Am I missing something here, or is my fuel pump pushing to much fuel?
Also I have a hesitation on acceleration from a stop.

 

Any vacuum line that's sucking fuel is going to make your engine run way too rich. Can you check that part of the carb to make sure that parts that need to be sealed are, and passages that need to be open are not blocked?

I've never worked on that carb before, but is the bypass valve controlled by a diaphragm? Is so, it may be cracked and leaking. Just guessing here.

 

I've checked everything vacuum wise and found no leaks. The by-pass valve may be malfunctioning which is next on my list to replace after I pick up the new fuel pump. Regardless I'm going to change the pump considering it's the original and only 20 bucks.

 

What carb do you have? The stock one should be a Ford Autolite 2150 I believe, but you refer to a "pump by-pass valve" which so far as I know is part of the accelerator pump circuit on a Weber carb.

Mechanical fuel pumps cannot "push" more than their rated pressure. This is because the pumping pressure is produced by a compressed spring acting on a diaphragm. The mechanical arm or rod that is driven by the camshaft lobe doesn't pump the fuel, it merely compresses the spring which then in turn pumps the fuel via the diaphragm.
I apologize for my not very good explanation, no doubt there are better explanations out there.

Anyhow, I would imagine the excess fuel problem is due to the needle not closing in its seat as it is supposed to. This can be caused by improper adjustment, a float that leaks (and thus sinks), a damaged needle tip or binding of the needle and seat.

When you shut the engine off, look down the carb to see if fuel continues to drip out of the booster venturi. This would confirm an overly high fuel level in the bowl.

The shop manuals of the 1960s used to recommend final float level adjustments made on a running engine with the top of the carb removed. That was a pretty sure way of knowing the level was correct, but is an obvious fire hazard if the carb overflows.