Sudden extreme rich condition

[MP81]

Hi there,

So as of a week ago, I went to move the car ('81 Z28, LG4 305 - CCC Q-Jet) around (to test an issue with the speedo cable I was having) and I noticed the car was smoking pretty heavily at idle - not blue smoke, a faint gray smoke with some black in it. And it did not smell like oil at all - definitely smelled rich as hell.

I just started it today (to test my fix to the cable) and did confirm it is absolutely running insanely rich (pretty sure it's spitting raw fuel out of the tailpipes), and after pulling the car into the garage and getting it positioned (tight garage), even with the garage door open, it was nearly impossible to stand inside without your eyes and nose stinging. The car is idling quite high too, and if you give it throttle it's hesitant to climb (bogging, I'm thinking). The smoke is not just at idle, it also smokes if you increase throttle as well... The insides of the tailpipes are black, and I've only put about 70 miles on the car since installing the new exhaust.

Thing is - it wasn't doing this a few weeks ago, after I got the headers and dual exhaust on, or anything (little smoke, but that may be valve seals, or just the forming lube).

Is the float stuck? What could cause it to suddenly run so insanely rich, all by itself?

I'm thinking the carb is looking like it needs a full rebuild - or is this something simple I've overlooked?

Thanks!

[429bbf]

i would check the choke pull off and see if it has developed a vacuum leak , push it closed hold your finger over it and see if it stays if not its bad fwiw

[MP81]

Would that cause it to run that rich though?

Is it possible to pull off the top section of the carb (on-car) to see if the float is stuck?

[429bbf]

yes it would pul the air cleaner and see if the choke is opening all the way if it is that is not your problem . yes you can take the top off with it mounted on the engine  i don't like to bend over that long i like to work on carb on bench . you should be able to tell if float is stuck . shut off car and look down carb ,you should see gas running down the intake . fwiw if the carb has never been apart buy a good kit from cliff and rebuild it so you know what you have . make sure you keep track off all the adjustments so you have a good starting point to tune .that carb has electronic metering rods you may have them stuck open .

[Cliff Ruggles]

Idling too high and running rich is most likely related to the choke pull-off or electric choke.  Check those items first.  If the float has failed it would flood out and not run at all.....Cliff

[MP81]

The linkage coming out of the pull-off (I think) seemed extraordinarily sloppy when I was playing around with the carb the last time...I don't recall it having so much play before, but I can't say for certain that I messed around with it prior.

[429bbf]

did you somehow unplug the choke ? once you take the air cleaner off and fire up the car you will know soon whats wrong open the choke by hand with it running and the car should run fine .turn the key on for 1 minute before you start the car and the choke should start to open a little if its working correctly.if its working and you start the car and it doesn't open all the way in say 3 minutes depending how cold it is.ether the pullout is bad or your vacuum hose going to it is unplugged or bad .fwiw

[MP81]

Didn't unplug it - I did check that. I crimped on a new connector (the stock one was long gone) after putting the headers on, real tight fit on the spade.

I will check to see if the choke is opening all the way, hopefully this weekend. It'll be in the high 40s so it might take a touch longer.

[MP81]

Started it up today - this is as far as the choke blade opened after running for about 5 or 6 minutes. By the time I shut it down, it was idling up near 2k, and revs were real slow to come down when I did rev it up to try and get it to drop down.

It was still smoking, but didn't seem as bad as the last time, maybe because it was colder out? May have been a placebo effect, too. 

The vac hose is still good between the pull-off and the carb.

[Cliff Ruggles]

Replace the electric choke.  It should be fully open in about 2-3 minutes.  We have USA made ones on the website, and they come with a new connector for the wiring harness......Cliff

[MP81]

That probably has been the cause of the idle issues all along. They went away in the summer, since it was warm out, the coil probably worked properly.

Maybe it's how it is designed to work, but if I were to pull, manually on the choke blade linkage, it would stay down until I opened the throttle blades.

So, replacing the choke should likely solve the rich issue as well as the funky high idle and slow rev drop?

[77cruiser]

How tight do you have the choke set? I set mine so they just close at 65-70 deg.

[MP81]

No idea - I've never adjusted it.

[429bbf]

couple of things . do you have good voltage at the chock with key on or running ?also is the car running in the photo? if it is your pulloff is bad fwiw

[MP81]

I did check for voltage at the choke, and if I recall correctly, I did have it.

And no, I took the picture just after turning the car off.