Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Difficult hot/wam restarts...Ethanol?

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brown7373:
The Q-jet on my 72 Cutlass 7042250 is rebuilt stock, using new choke tubes and choke stove.  Restarts when warmed up are more difficult than I think they should be.  Engine temperature is 180-190.   Is it the 10% ethanol in the fuel?  I see zero evidence of any leaks.  The new float is set at 1/4 as per the spec. 

It starts perfectly when cold, idles fine, does not stumble and can be driven away immediately with no issues.  It is smooth and responsive, and I would say as close to perfect as possible...except when restarted warmed up.  The plugs were all drilled out, threaded and Marine-Tex used on screw in plugs to seal everything.  It has a new Cliff kit with float and all the good rubber parts.  It can sit for weeks, but once to the floor and it fires and runs just like it should.

Very recent tune-up with new everything set to specs.

Cliff Ruggles:
Difficult hot restarts can be related to mixture screws set too lean or too rich.

If the carb is leaking someplace, you would notice vapor coming up out of it right after hot shut-down, something to check but a leak that big the carb would be empty by the next day.....Cliff

429bbf:
i don't know if your doing this ,but this was my problem . i was stepping on the throttle on hot starts. it was a bad habit i had with my original cards. when i switched to quads i caught myself still stepping the throttle down about 1/2 way and was actually flooding the engine. once i quit the problem went away. hth

brown7373:
I do put the pedal 1/2 way down, like it says in the manual.  I drove these cars back in the 60s and 70s when they were new and the gas wasn't laced with ethanol.  I used to just reach in through the window and twist the key, and it would always start unassisted.  I will take another look at the idle screws, as I might be a bit rich. 

brown7373:
I adjusted the idle screws 1 full turn in from the initial 4 turns out.  At that point, the idle slow slightly and it ran just a touch rough.  It started fine cold, but a restart and it wouldn't idle and kept stalling.  I adjusted the screws out an additional 1/4 and the idle smoothed out.  The hot restart idled fine, but it was back to the previous condition of not starting as easily I think it should. 

I have no obvious vacuum leak, but if my throttle shafts are leaking, or some other vacuum leak, could that be causing this condition?

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