Thanks guys! Going to have a go at rebuilding the carb tomorrow, but I can't seem to find a vacuum gauge anywhere to help me set it up properly? Anyone know of somewhere I can loan/buy one? Auto Zone, Advance and O'Reillys, none of them have them in stock, they have to be ordered in...

bkaul - Please don't apologize for trying to help me out. It was me that was way off with the description of what was happening and you were trying to help based on the symptoms I'd mistakenly given you. Now we might be on the right track though

 

Locally, you might try a store like NAPA or Carquest too, or try Sears' tool section. If O'Reilly et al. have to order them in, is it just from the local warehouse (same/next day), or longer?

Fastest source I know if no one in town has one in stock is to order from Amazon - if you're a Prime member, 2-day shipping is free and next-day would be like $5:
http://smile.amazon.com/s/ref=nb_sb_...s=vacuum+gauge

You should be able to get by without one in a pinch though. Get all the bench adjustments set on the carb according to instructions, then once you get the engine started, fine-tune by listening to RPM rise/fall. It's not quite as precise, but workable.

 

bkaul is the line from the intake vacume or gas?

 

Getting back to your power valve.....If it is blown, it'll still start, albeit a hard start, and you'll smell the unburned hydrocarbons (rich smell) enough to make yer eyes water.

A test for the power valve: turn the mixture screw(s) all the way in - if it still runs, the power valve is shot. An easy fix for a new one. I think a 6.5 (stock) is a good all around valve.

 

On the evap system? Not sure that's really relevant to the OP's problem at this point, but what the heck:

The older style, with the round canister, had:

• 1/4 or 5/16" vent line from the gas tank (for vapor recovery)
• 3/4" hose that, as I understand it, ran to the air cleaner, though I've never actually seen the routing of a complete system from this era in person to verify.

The newer style, which I'm setting up with the plastic canisters, is a bit more complex, at least in the mid-80s configuration - I'll post the vacuum diagram in my build thread if I haven't already, but the short answer is it tees into the line from the PCV valve to the base of the carburetor, but is controlled through a vacuum-actuated valve by the same control signal as the EGR.

 

Right. So managed to get a hold of a pressure/vacuum gauge and hoses. Put it on the fuel to the carb to stay of with and was showing consistent 7.5psi of fuel pressure to the carb. This was with the supply lead to the distributor disconnected and cranking engine over. Might be useful to note I bypassed the electric pump I just installed and got the same pressure either way. Reading the Holley web site and they say up to 7psi is still ok? Should I regulate this or not?
Ran the engine and turned in idle screws ask the way and it still ran so looked like power valve shot. Started a rebuild on the carb tonight and the diaphragm for the power valve is stretched out so looks as though it's not been seating properly. Which would explain the over rich running, fast park idle, accelerating when put into drive and the flooding etc.
First time rebuilding a carb but should hopefully have it done by tomorrow so wish me luck!

 

OK, so a little bit of an update...

Had the carb off and rebuilt it. After a bit of messing about with leaking seals, it's now sealing but delivering WAY too much gas, but I still need to make the adjustments to the floats in the morning. I've adjusted the idle screws, but I need to mess about with those tomorrow as well, now that I've got the vacuum gauge...

BUT ran into another problem... Whilst messing about with the carb, I was looking into the linkage that runs between the transmission and the carb and it seemed real loose. So got under the truck and see that it doesn't move when the gear shift is moved from park to drive, neutral, reverse etc. Started looking YouTube and there's a video saying how this carb needs to have a spring on this lever and it needs to be set up etc, etc. OH and a load of comments about how NOT having this linkage set up right can fry the tranny! SO, it looks as though previous owner has dropped another one on me. Like I've said, this is my first sortie into the carb world, but even I would think that you need to have the carb knockdown attached and setup properly to change the rpm when you go into drive etc? Thoughts anyone?

My neighbor has been able to order one off eBay to be delivered to his house (Kit isn't available in any store near me, and I'm leaving the country shortly for a few months) and he's going to have a go at installing it while I'm away, but I can't believe that the truck has been running this long without this on? Could this also have been the reason I've been getting the over supply of fuel when it's in drive? Also, can anyone tell me how the linkage moves on the tranny? It looks to be connected to a rob with a nut/bolt, but is it specific fit, and should it be tight?

The more I dig into this, the more problems I seem to be finding, but I'm hoping the light at the end of the tunnel will be turned back on before too long! The way I'm looking at it right now, at least I've rebuilt the carb if I can get it all set up right!!!

 

What transmission do you have?

On Ford automatics from this era (C4, C6, FMX), the rod from the carb to the transmission is a kickdown: when you get to a certain throttle position, it tells the transmission to downshift. These transmissions will also have a vacuum modulator to control line pressure (and thus shift points). On these, the kickdown function is the only thing you'd lack without it - it just wouldn't downshift as rapidly for passing when you jab the throttle.

On the later AOD (and many GM transmissions), it's a throttle valve (TV) rod that controls the line pressure in the transmission directly based on throttle position, without a vacuum modulator. For TV setups, the adjustment of this rod is very important.

In neither case would the rod do anything when you change the shifter position on the transmission - it's actuated by the throttle position and is a control input to the transmission.

It also has nothing to do with the drop in RPM when you go from P/N to D/R - that's just the fact that you put a load on the engine without changing the throttle position: it's inherent in engaging it in gear.

 

Nice explanation, thanks bkaul! You've set me on the right path again!

From what I can gather, I've got the original C6 transmission in the truck, so it definitely sounds as though it's a transmission kickdown, and now thanks to your description, I can rule it out as part of the current problem. But am I right in saying that it should be connected, with the spring attached? Would it not returning to it's proper position cause early or late shifting of the gears? Trying to wrap my head around it a little as this is also the first time for me working on an automatic transmission (LOT of firsts for me on this truck LOL).

One last thing, is that with the fuel pump making 7.5psi and the Holley videos recommending a high of 7psi with an optimum of 6-6.5psi, should I put a regulator in the fuel line as well? I find it hard to believe that with the exact same fuel pump spec as original that I would need to install a regulator now, even though I believe this to be an aftermarket carb.

Sorry for all the questions guys, but we've all got to start somewhere!

 

On whether the kickdown needs a return spring, I'm not certain. As for symptoms, if it's not hooked up (never kicking the transmission down), your normal upshifts would be unaffected, but downshifts for power when you step on it would be delayed. If it's hooked up but not returning, it would tend to think you're always stepping on it, and be biased towards lower gears/higher RPM (delayed upshifts).

On the fuel pressure issue ... I'd be inclined to try adjusting the float level and see if the needle valves will seal OK and maintain fuel level in the bowl(s). If it's flooding on you and you can't get it set right, then you'd need to regulate it down.

 

What I've found is that it shifts up the gears quicker than I would expect, to the point where I can go round the development with no gas on and in 2nd gear, sometimes 3rd with it accelerating. The other thing though, is that when stopping/braking, it doesn't drop down the gears as it should until I'm almost at a complete stop, and then it'll shift down.

Watching the Holley video about it, it says to remove the locking screw that's normally found on the lever, but that sucker is in there, so I'm wondering if it's only functioning because the throttle lever is hitting that screw (which it does). Unfortunately, the only way I'd be able to see what was going on is to either stick a go pro under the hood and drive round the development, OR find a midget who can watch it while I drive...

My neighbor has ordered the kit and hopefully it'll solve the issue with the quick up shift and slow down shift once it's installed.

As for the carbs... I'll see how I get on tomorrow with the setup as I didn't start tonight because of losing light. The power valve was definately passing though, so hopefully I've managed to solve one problem... Just a lot of faffing about to get the bloody thing set up now...

 

Hmm ... not sure I'd expect that behavior from a missing kickdown linkage, but we'll see. Upshift points are more a function of line pressure, which is a function of rpm and the vacuum modulator.

 

Update part 2:
Finished the rebuild on the carb last night and got it put back on, but because of the time and living in a town home, couldn't run it up to test.

Ran it this morning and made adjustments to acceleration pump and floats. When neighbor got home, we adjusted the idle screws, curb idle and idle when in park. Truck is now running and sounding WAY better than ever before AND more importantly ISN'T stalling out when I give it some gas. And I gave it a good bootfull of gas on the straight bits round the development much to the delight of my HOA I'm sure...

Just waiting on the transmission linkage spring kit to come through and then that'll be installed, but for now, we're running SO MUCH BETTER!

Special thanks to bkaul for his patience during my questioning and giving me some much needed info and guidance through this. Hopefully all is well again with the HULK!

 

No problem. Glad you got it running again!