Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

'75 Eldorado Q-jet Driver's mix screw no impact

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old cars:
stop spraying carb cleaner . Throwing more parts at it won't solve mixture screw not responding. Windowed/ non windowed, brass float or not, bushings, all of these have little to do with your problem if the one mixture screw is truly not responding at all.
If you have Cliff's book read it. If not , get it. You need an understanding of how the carb works. Clean your circuits.
I'm not saying the use of good parts ( as suggested ) was not good advice.

Benji808:

--- Quote from: old cars on September 06, 2021, 05:14:05 AM ---stop spraying carb cleaner . Throwing more parts at it won't solve mixture screw not responding. Windowed/ non windowed, brass float or not, bushings, all of these have little to do with your problem if the one mixture screw is truly not responding at all.
If you have Cliff's book read it. If not , get it. You need an understanding of how the carb works. Clean your circuits.
I'm not saying the use of good parts ( as suggested ) was not good advice.

--- End quote ---

My assumption was that if there was a leak in the side of the carb, the impact on the air fuel mix would render the mixture screw on that side mostly irrelevant, and addressing that would be a good first step so that I can get an accurate understanding if I do have an idle circuit issue. Is that not the case?

Cliff Ruggles:
Good results ALWAYS start with good parts, and the correct parts. 

The very FIRST thing I do when I get calls to the shop or emails  from folks with carburetor issues on any sort is to have them install one of my kits.

It was a natural course of evolution that I went into the parts business anyhow, so here's a short version of the long story.  WAY back when I went full time into this business we got really busy so I brought in more help and were cranking out hundreds of carburetors.  I was using brass floats in them and the accl pumps and N/S assemblies from the two biggest suppliers.  Things went well initially for a few months, then one by one we started getting carbs sent back here.  The issues were either the float filling up with fuel and sinking or the accl pump or seal failing.  The seals were swelling up and sticking in the bores and the pumps were pulling apart lacking a crimped ring to keep the plastic end on the shaft.  Before anyone asks the answer is yes, the seals on those pumps were "blue" in color.  I have over 50,000 of them here in spare parts removed from accl pumps over the years.  If you think they make the grade just pay the shipping and I'll gladly send you a bag full of them.

I immediately switched to nitrophyl floats and cured that issue and coaxed them to have a crimped on retainer added to the pumps.  They continued to supply the "soft" blue seals on the pumps however, so to this day I still have to remove them and install a seal that is impervious to any type of fuel or fuel additives.  I didn't like their pump springs (coil binding) or their selection of power piston springs so had those custom made as well.  It was a little painful at first as USA companies woln't even talk to you for less than 1000 pieces per order and most want at least 10,000. 

As soon as I started installing all the upgraded components comebacks went to ZERO, none, NADA.  So when I recommend installing one of my kits it is for good reason as it takes the use of crappy parts causing any issues OUT of the equation.

Anyhow, getting back to the task at hand here, most of these carburetors need primary shaft bushings installed in them for two reasons.  It eliminates a vacuum leak at that point and insures that ALL the incoming air is filtered (assuming no other vacuum leaks anyplace).  Additional air coming in around the primary shaft is just like adding more bypass air so it does effect idle tuning.......Cliff

Benji808:
That's quite the history - thanks for sharing, Cliff!

As you said, to the task at hand - sounds like I need some bushings, and probably new base plate gasket and throttle body gasket, as the chances are not zero that I screw them up during removal. Can I buy these things - bushings and gaskets - from you, or can you provide a source?

I've watched some videos on the "drill in" technique to install the bushings...I may beg/borrow a moment from a really busy guy in town to help me, or I may attempt...any advice you have would be appreciated.

Cliff Ruggles:
Tread softly watching Youtube videos as most that I've seen are done by folks who really need to keep their day jobs.  I tried watching a few, but the fat lady next door yelling at her kids, the wind blowing in the microphone and having to listen to everything the guy did since he reached puberty BEFORE getting to the task at hand was too much for me!

Seriously, LOTS of information on there that isn't accurate and for sure don't watch the videos about taking them apart and putting them back together.....HORRIBLE!

I use top quality re-useable gaskets in my kits.  Most others use the cheaper "skinned" back gaskets.  They stick like super glue after a short time in use so likely you'll have to get out the razor blades.

I can get you whatever you need and manufacturer of the best bushing install kit out there.  Shop is 740-397-2921, 7am-4pm M-F EST....tks....Cliff

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