No, actually my canister is still hooked up. I even set it up to vent full time by removing the purge TVS and ran the vacuum line for the tank pressure valve directly to a vacuum source.

Yes i disconnected 4 wire connector. I have no pic but it goes from distributor base toward firewall and into the main wire harness back there. If you reach back tje right next to the oil pressure sender you will feel it

 

so if im reading that correct, your supposed adjust the lean/rich screws first while its apart, then you use the dwell meter to get 30 degrees by turning the mixture screws on the bottom of the carb?

edit:just found the tools i needed in the Thexton 2500. cost me 85 but it will be worth it not to have to put another carb on

 

this is the kit i ordered

in my opinion i think the MCS was causing the rich condition since it was never properly adjusted when i replaced it. all i did was count number of turns to remove, didnt even bottom it out. since the metering rods plug the fuel flow off i bet they are not going deep enough into the jets. hopefully this helps with my problem, do these gauge tools for the air bleed need to push down on the plunger to get the desired measurements? ill report back when i have made the adjustments

 

do these gauge tools for the air bleed need to push down on the plunger to get the desired measurements?

Yes. What you are doing is setting the rich stop, the lean stop, and the travel distance to create the proper "window" for the ECM to operate within. This gets set first, then the mixture screws are used to fine tune for your 28-32 degrees of dwell.

 

i went to put gas in the tank and as i was taking cap off loud hiss could be heard indicating built up pressure.

Check again. Is the hiss from vapors pushing out (pressure), or air entering (vacuum)?

 

That is a really complete kit - NICE.
BTW, C3 means CCC - Computer Command Control.

 

If you haven't done it already, plug the 4 wire connector of the distributor back in.
Otherwise, you have no advance. It is done electronically by the ECM.
That connector is only disconnected while setting your base timing.

 

If/when you go back inside the carb,
1) put a viton cup on the accelerator pump (should be blue or green)
2) set/correct the float level
BEFORE you do the settings for the MCS.

 

i just took the cap back off and nothing happened, no sound no hiss. it was a hot day when it made the sound, i just assumed it was pressure release. ill keep checking that one
the screws on the bottom right? i probably connect the leads directly to the wires on my MCS right?
yes i plugged it back in when i was done, and i pulled the power wire for the ECM to clear the code from unplugging the distributor

can you give me little more info on this? what is a viton cup? the cardboard ruler included in the rebuild kit will be used to set the float, correct?
my accelerator pump has blue rubber on it



the idle air bleed i think i understand, by the long straight end of the shaft and the tab it looks like i will turn the screw until it makes contact with the other end of the tool. the MCS i dont think i quite understand how it will adjust, when the lean screw does not tighten against the gauge tool. maybe ill have to see it in action to understand it better but the tool rests on the plunger and main jet while i will be tightening down the solenoid. will the plunger not touch the gauge tool at first until i have turned the screw enough turns?

sorry for all the noob questions, but im learning so thats a plus. i appreciate the help NoEmissions84TA has provided

 

the screws on the bottom right? i probably connect the leads directly to the wires on my MCS right?

The screws on the bottom are your idle mixture screws.
Supposedly, there is a open wire connector (green) by the heater core that is used to connect the dwell meter (other lead to ground). I never did it that way. I pushed common pins into the wires connected to the MCS and connected right there. Some will say that there is a difference in the readings between the 2 places.

what is a viton cup?

Your accelerator pump is what gives the shot of gasoline into the carb when you press the gas pedal. When you pump the pedal twice in the winter, you are using this pump to shoot gas into the carb to help the engine start. The rubber "seal" on the end of this pump is the pump cup. Viton is a better material that is resistant to the additives in todays gasoline that cause the regular rubber cup to shrink, becoming inoperative over time.

my accelerator pump has blue rubber on it

Good chance then that you already have Viton. Use your fingers to work the rubber out to a slightly larger diameter before the carb gets reassembled.

the cardboard ruler included in the rebuild kit will be used to set the float, correct?

Yes.

the idle air bleed i think i understand, by the long straight end of the shaft and the tab it looks like i will turn the screw until it makes contact with the other end of the tool. the MCS i dont think i quite understand how it will adjust, when the lean screw does not tighten against the gauge tool. maybe ill have to see it in action to understand it better but the tool rests on the plunger and main jet while i will be tightening down the solenoid. will the plunger not touch the gauge tool at first until i have turned the screw enough turns?

You are getting it. Read this guide. It is step-by-step with pictures. https://www.hemmings.com/magazine/mu...e/3720231.html

Also look back at post #40.

 

That is an interesting read, ill keep that handy cauee there are points in there im not gonna remember when i do this so i can refer. Ill pull the carb tomorrow and bring home. Ill check well plugs too to make sure they are not leaking



I think i understand it now but ill practice on my old carb before i adjust my good one

 

I have an update on the venting issue for anyone that can help me. I went to the storage facility where the car has been sitting for the last 4 days untouched. I unscrewed the gas cap and the hiss was heard. I looked underneath and i foumd this,

Is this the vent in question? I still have my canister hooked up so i dont understand why its doing this. When i removed the fuel line hardly any gas came out, last time i removed this line i had gas spraying all over my engine and had to hold a rag over the line in order to jam a plug in it. It was as if there was pressure, but this time no pressure, no spraying

 

that is a two way valve. it allows air into the tank to equalize pressure AND vents the tank under too much pressure.

the system is designed to allow moderate pressure to build up in the tank in order to force the fumes through the charcoal canister. too much pressure being bad, this valve relieves pressure when it gets too high. you can test this valve by connecting an air line up to your fuel return line. as you introduce the tank to greater air pressure from your compressor you'll hear this valve vent it.

the tank will build up pressure all on its own, even without the motor running. as the tank, and the gas inside it warms up, the pressure inside it will increase; due to the ideal gas law and the vaporization of additional liquid fuel. as it cools down the inverse is true.

 

Where is the fuel return line so i can check this? Shouldnt the tank still be venting through the charcoal canister? The pressure buildup amount i witnessed should have been more than enough to force the venting


Also what are my options if it turns out to be bad? If these are not produced i imagine it will be hard to find one. I looked on ebay and found "vented" gas caps could i get one of those to solve the problem?

 

Found a thread about cleaning it so i took mine apart and cleaned it up. I have it drying now

 

No, actually my canister is still hooked up. I even set it up to vent full time by removing the purge TVS and ran the vacuum line for the tank pressure valve directly to a vacuum source.

How is the tank pressure valve supposed to open without a vacuum source (engine running)?
This situation is just like when you leave your plastic lawnmower gas can in the sun and it swells up. Or when it is cold outside and the can is sucked in.

The fuel return line is at your block mounted mechanical fuel pump. It is the smallest diameter 1/4" line.

 

Everything is still in place except for the CCV and purge TVS i ran the vacuum line into the carburetor vacuum source. I asked about removing the tank pressure valve but i was told thats not a good idea because the fumes need to build enough pressure to open the valve


i understand what you are saying but i was told to keep the tank pressure valve, should i ditch it?

 

i understand what you are saying but i was told to keep the tank pressure valve, should i ditch it?

No, you want to keep that, and the way you have it hooked up will work.
Get the UFO valve back together and test for proper operation.
If it does not work, you can replace it with one of these: https://www.summitracing.com/parts/tnk-vvr
There is also a member here trying to reproduce the UFO using a 3D printer.
https://www.thirdgen.org/forums/hist...ml#post6156548

 

I got the valve back together, and was able to blow into it. With a little force the valve opened, im gonne put it back on the car and try to pressureize the tank to see if it will open. It didnt seem that bad inside but from the looks of it, it wint take much to keep these from opening

 

ok i got the valve back on the car i also blew into the hose to see if maybe the hose was clogged. i could hear air escaping the gas cap until i tightened it so the hose is working right.


on a side note i started taking the carb apart and i think i found my float problem. the hanger for the needle is gone. i looked inside the float bowl and its nowhere to be found. this is exactly how it looked when i removed the MCS, needle was not even attached to the float

 

i think i found my float problem. the hanger for the needle is gone.

That might be part of the problem. You're getting there.

 

That valve works in 2 directions:
1) if the tank pressure should get to be over 6-7 psi (I have read), it opens to vent the tank
2) as fuel is consumed, it allows air IN. It's like if you turn a soda bottle completely upside down. Nothing comes out. Poke a straw in to let air in, and it comes gushing out.

 

So another issue cropped up. I was taking the metering rods out and one of the springs broke. I took both springs from the original carburetor and now when fully extented the rods dont touch the plunger. I know when the air horn is on the plunger will not extend as high but will this change operation of the metering rods?

I also stole the needle from original carburetor so it has a hanger again

 

the installation of the plunger and needles looks normal.

When the gasket and air horn is installed (and the rich stop screw in the air horn is set correctly) the plunger will contact the needles. the rich stop screw limits the plungers upward travel and the lean stop screw (which is also the screw that holds the mcs in place) limits its downwards travel.

a good start point is to set the lower screw in four turns out and then adjust the screw in the airhorn until you have 1/8" of travel for the plunger. with the airhorn and gasket in place you can measure this travel with a small rod (maybe a secondary needle) placed through one of the vents or the IAB opening (with IAB removed temporarily). exact settings are not terribly important, the dwell is fine tuned with the IAB.

the float needle doesn't really hang on the arm, the lever arm forces it down onto the seat. the clip is really just to keep it in place, I've seen them work perfectly without the clip. best to use it if you have it though.

 

Thank you naf.
I will add:

I also stole the needle from original carburetor so it has a hanger again

It is bad practice to mix needles & seats. Just change the small wire clip.
BTW, it does not go through the holes in the arm of the float, it hangs over the edge.

You are doing fine 87tunedport. Keep going.

 

I actually had that thought too and i replaced the needle seat, needle, hanger, and float from the rebuild kit

I set the float at 11/32, and hanger is set correctly, however with the hanger in place the needle lifts out of the seat slightly when the float is all the way down. I know it is supposed to fill the bowl back up when it gets low enough but i thought it would just release pressure on the needle and the pump pressure would open the flow until the float arm puts pressure on the needle to close flow. I cant really explain it how i want to i just didnt think the arm would lift up on the needle. How much pressure does the fuel pump put through the carburetor?

 

How much pressure does the fuel pump put through the carburetor?

More than 6 psi is supposed to be able to blow the needle off the seat.

 

So in other words the float arm is not supposed to be lifting the needle at all, it just releases pressure and i should adjust the hanger


small update, i just checked the gas cap and no hiss

 

IIRC, GM did that on purpose (the clip) so that the needle would not get stuck in the seat. The addition of the clip pulls it off the seat at full float drop. I believe you are adjusted correctly. But I am trying to remember back a long way.

 

Ok ill leave it like it is for now. Just afraid if the needle cant shut the flow off and the bowl overflow

I appreciate the help now i just have to adjust the carb and i can get it back on the car and adjust dwell.

I got the EGR and idle stop ordered and ill i stall them after

 

hey so i still have the plug in place for the rich stop screw. how do i get it out? or should i just leave it in consideration that maybe with the plug in place it is still preset?

 

UPDATE: i got the kit today. i got the MCS set using the shaft tool. when i was checking the rich stop i got 10/32 at full depress and 5/32 released so would the ECM be able to operate with 5/32 plunger travel? i was gonna adjust the air bleed but do i need to get the lean/rich stops set first?

edit: got the rich stop adjusted by turning the stop out enough to 6/32 at full release and 10/32 at full depress so now i have 4/32 plunger travel

got the air bleed set with the candy cane tool and idle mixture screws 3.5 turns out from seated.
i will install on the car tomorrow

 

first pic shows plunger depressed 2nd is released and against rich stop screw.

if i messed something up or something does not look right let me know, ill be installing back on the car tomorrow

 

Everything is here: https://www.hemmings.com/magazine/mu...e1502147044667

I think you are in the ballpark. Good luck tomorrow.

 

Yep had that article out while i was doing it

 

Well i got the carburetor installed and shes running again. No more low idle but still rich so ill get my dwell meter on there and fine tune it. And set TPS, question, do i use OHM or DCV when checking TPS?

 

DCV from center wire to ground. My 84 LG4 305 TA called for .48v at idle.

 

Someone correct me if I'm wrong here.

You say you are still rich. Assuming no other causes, when you adjust the carb trying to get the 30 degrees of dwell, if you need to go way beyond your preliminary setup adjustments, then set those back to where they were and turn each mixture screw in 1/8 of a turn and try again. Follow what I'm saying???
Actually, before you adjust anything, verify both idle mixture screws are both working and each has approximately equal control. You are at 3.5 turns each now. Turn 1 in (count the turns) and see where the engine stumbles. Then set it back and repeat for the other screw. They should be nearly the same.
Fine tuning the MCS must be done at your low idle and in closed loop (warmed up with ECM controlling the idle mixture).

 

No i dont quite follow. Do you mean resetting the mixture screws back to 3.5 turns and turning the rich/lean stops?

Turning the mixture screws all the way in will stall the engine correct? If not then the screws are not working right?

The 2nd time i fired the engine up it did not run as rich. Maybe this is of no importance but i never refilled the fuel bowl before i put the carb on the car so it took a couple key turn and about 15 seconds before the engine fired. Then it shot up to 2200 and i had to turn the fast idle down. I do not believe the choke is properly set

 

do not assume because the dwell meter is showing a steady reading that the motor is running either rich or lean. it will likely be stuck in its last known good setting.

you'll also need to adjust it until you see the needle start wavering, showing that it's responding to O2 input. the dwell will still vary in closed loop with throttle, VAC and rpm changes but the closed loop changes will be steady with no wavering.

 

Well the car is not rich anymore, or its not noticable. I turned both mixture screws all the way in and motor still ran smooth

Hopefully the dwell meter will come tomorrow so i can adjust it and go from there. I adjusted the TPS to .48 and now overdrive comes in later. Used to engage pretty quick after 3rd but now it dosent unless i let off accelerator

 

I turned both mixture screws all the way in and motor still ran smooth.

This might be a problem.

 

You say that like i may be looking at a new carburetor?

Is there anything from the rebuild kit i can use on the carb to fix that problem? or something i can adjust? what causes that problem?

Guess i better start saving my pennies huh?

 

adjustment could be off enough for it to still idle with the mixture screws in. don't give up on it yet.

 

I made all the internal adjustments using the Thexton tools what adjustments do yoy recommend i make? Im guessing something with IAB?

 

At this point, you need to see what the ECM is seeing and therefore, trying to control, or is not controlling.

 

In other words i need the expensive scanner that can show live data?

 

I've never had to use the expensive scanner with mine, just the jumper wire at the ALDL port. But you say you have no codes. I think your carb is probably fine. Something else might be going on.

 

I have no SES light, does this system do KOER tests like Ford OBD? I ran test with KOEO and got nothing

 

Would a faulty O2 cause a problem? It could be working but giving back faulsr data?

I know i have to be in closed loop to adjust dwell but i thought i could still use idle mixture screws to affect idle