fazang

I just rebuilt my #7029207 with dat code #2815
thought i followed the instructions well....put the carb back on the car today.

turn key 8 sec, then turn off and pump pedal, turn key 8 sec, then turn off and pump pedal, turn key again and she cranks right up and ran.

after 1-2 minutes i back out of garage onto level part of drive way 5o feet maybe....get out and open hood and she starts to stumble and finally stalls.

I thought i had the idle mix screws wrong so double checked and they are where they were before i started all this so doubt that is it.

as of now i can start the car at will but need to keep burping the gas pedal to keep it running....?
any idea what i did wrong ?

i kept the revs UP and drove in 1st gear back into the garage, now scratching my head.... could i have messed up the float height ?? did 3/16 of an inch....

will start reading LARS papers again.

TIA
-ALF

lars

Alf -
From experience, I can tell you that it is absolutely impossible to troubleshoot carb problems via e-mail or Forum posts - the carb needs to be inspected in-person in order to identify the issue. There are about a dozen problems that can contribute to the symptom you describe, including:

Lean idle mixture
Plugged IFR
Incorrect throttle plate gasket or airhorn gasket
Low APT
Low float
Warped airhorn
Vacuum leak/component not hooked up
Vacuum advance control hooked up to incorrect carb vacuum source
Debris in needle/seat
Needle clip installed backwards
Check valve in filter not unseating at correct pressure
Secondary throttle plates not fully seated/closed

If you can't get it running, send it out and I'll test it and fix it.

Lars

fazang

thanx Lars,
I made clips of the reassembly and will make one 10~ min vid of the rebuild and maybe someone on the forum will see a big mistake ?
aside from that i guess i will check all you posted here to try and rule things out....what a bummer.
-ALF

fazang

okay DQ time....
from 13sec to 21 sec in this vid
http://www.youtube.com/watch?v=-8tC6cn1KlU
you can see the the vacuum advance line from front of carb to dizzy....
at 21sec you see the rubber hose connect to metal tube !
I just saw it was disconnected there, would that prevent car form staying running????
i don't think so but wanted to ask.....


also i made PART1 and working on posting Part 2 of the reassembly.
http://www.youtube.com/watch?v=1CqB4ujQiqw

EDIT:
here is part 2 of the reassemble
carb_rebuild_Part2

here is part 3 of the reassemble
carb_rebuild_part3
-ALF out...

Vette5.5

Sure sounds like a fuel starvation problem to me. Maybe an improper carb float valve setting, fuel pump, or plugged fuel filter. Fuel filter problems are more common than you'd think, as knew a few guy's having this. Would idle fine, but when trying to drive under throttle a few minutes, would just dye. Helped a guy with this. Pulled the carb filter, and hammered a punch through it, to get him home. Tried blowing/pumping fuel through it first, but nothing.

lars

Alf -
I'm on dial-up, so I can't see video. If you need assistance, just send me the carb.
Lars

Shark Racer

Lars - I believe I read somewhere that the needle clip is not a necessary item... is this true?

fazang

Well I took carb off and made one change, put the old float in. Bolted back on car and it did the EXACT same thing, ran for good 2-3 min and then stalls.
I didn't try to restart it...

I'm starting to think the mechanical choke is moving from the coil spring thing that gets heated from intake manifold, and expands (not sure of proper name)

maybe as choke mechanism activates it's not getting enough air, i am sure there is a way to test that but i bet i need 2 peopel to do it.....

Shark_racer, when i tore mine down the needle was the kind without the retaining clip...FYI


-ALF out....

lars

You can remove the clip and run without it as long as the car never sits long enough for the fuel to fully evaporate out of the bowl. But if you put the clip on backwards, you can cause jamming of the needle and eratic needle/float level operation.

There is no stock correct needle/seat that is "the kind without the retaining clip." If you have the integral needle/seat, yank it out and throw it away and install the correct needle & seat.

Lars

fazang

I know you can't see my rebuild vids Lars....but i used the parts in the kit and they were the correct type, doubt Cliffperformance would provide wrong stuff...

only the float is the old one, maybe cuz mine is 1975 service replacement carb eplains the wrong type of needle being in there, or some Bubba was messin with it before i had the car...?
-ALF out...

lars

There is only one type of needle and seat ever used in any year Q-jet, and it uses a 2-piece needle and seat with a needle clip. No exception. Why are you re-using an old float on a new rebuild...? Replace it with a new correct float.
Lars

fazang

Sorry if i was confusing about the float Lars...
I only put the old float back in to rule out that i had set the new float incorrectly, as stated in post #8

I think i need to learn more about how this carb works in general when doing cold start....Specifically the choke.
Cliffs Qjet book maybe in my library in next day or two... ;-)
-ALF out...

EDIT: i added links to more clips in POST #4 incase anyone wanted to see my "handy work" 8-)

Shark Racer

Read Lars' paper on setting up the choke on a q-jet. I never thought I'd be able to figure out how a choke works and he got me on the money.

fazang

Thank you shark_racer, i did some searching and found a zip file of Lar's fixes for various problems.....The light at the end of the tunnel is i think i found something that sounds like ME !!!
it's in BOLD

Choke pulloff incorrectly adjusted
Results in: Poor cold-run characteristics, stalling when cold, flooding when cold, engine won’t stay running after cold start-up.
Comments: The primary purpose of the choke pulloff is to crack the choke open just a tad upon initial cold-start. If the choke is not cracked open, the engine will flood. If the choke is cracked open to far, the engine will lean out and stall. When correctly adjusted, the choke pulloff will open the choke ¼” as measured from the forward lower edge of the choke plate to the airhorn wall.

i really believe i can get this carb to work again, but need to understand it first...

-ALF

Shark Racer

You need to verify that the pulloff holds a vacuum as well. If it won't, it won't open the choke flap correctly.

fazang

tryin to ID some parts and figure what they do....anyone wanna take a stab at these ?


some more pics of my setup




trying to match up with what i read in here
http://www.whateveristrue.com/chevy/...et-4MV-4MC.pdf
P.S. ordered Cliffs book, but anxious to study-up....

EDIT:
1. secondary lockout lever (in my finger) what it do ?
2. fast idle cam (visible in same pic) what it do ?
3. choke pull-off (round white plastic thing) sorta get what it do ?
4. Thermostatic coil & rod (mounted on manifold)
-ALF out...

Shark Racer

Secondary lockout lever prevents the secondaries from opening while the car is warming up. Once the choke fully opens it releases.

Fast idle cam catches when the choke is closed and increases the idle speed during warmup.

Choke pull off dampens the secondary openins and also opens the choke air flap a little bit when the car is warming up.

Thermostatic coil & rod - as the bimetal spring heats up it relaxes the airflap until completely open.

lars

Alf -
Be aware that you're working on a commercially rebuilt carb, and chances are good it has dozens of weird problems that cannot be fixed with a rebuild kit. Be sure you e-mail me for my paper on "Commercially Rebuilt Carb Problems."

Lars
V8FastCars@msn.com

fazang

thanx
emailed you

better manual for my carb than link in post #16
http://www.tocmp.com/manuals/Carbs/R...20complete.pdf

-ALF out....

EDIT: worked last night and took carb off and put new float back in, double checked 3/16" float level is good.
using PDF file in link here pg13-16 got the fast idle cam set properly by adjusting fast idle cam screw.. YAY !!!
so car will start and choke works, bringing RPM up to about 2200, I tap pedal and Pull-off works and it attempts
to idle... but stalls. 8-(
On to the next step in "tuning" a carb i guess...

fazang

NEW development
1. idle mixture screws (both) all the way in and car still runs..... 8-(
2. put hand over choke to cover it with car idling and RPMS go up 8-(
3. also i had idle speed screw set to 1400 RPM and sprayed carb
cleaner around base of carb looking for vacuum leak, found one. Long
story short put gasket on wrong, between intake and carb base..

So, safe to say it's RICH, i read about this on some posts but need to
refind them to learn the WHY ? and HOW to fix.

Also
4. I thought i filmed the Venturi's with idle mix screws all way in
and watched FUEL goingdown the carb like a "little brook" AFA flow,
but camera died and vid is 1.01 MB and 2 seconds long... 8-( you can
see it but only split second. 8-(

So to Sum up...
1. i put the new float in and set to 3/16 of an inch
2. put carb on the car cold and watched it A. start B. choke works
and car warms up
3. tap gas pedal to test /see 2ndry lockout comes off, fast idle cam
comes off high step, and idle speed slows down. ( all that worked)
4. now i should be able to set / adjust idle mix screws but can't...
as stated above.
5. my dumbass guess without research is float is too high, need to try 1/4 inch

-ALF out...