Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Sudden extreme rich condition

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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

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