Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Q jet Bog

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greggome:
Had my 68 Q jet rebuilt by allstate carburetor about 6 months ago and its been working fine. I suddenly started having significant hesitation issues when i stomp the accelerator pedal. Car cruises okay though I have noticed a very slight hesitation feel when changing gears and press accelerator normally. Under heavy acceleration the car bogs and almost sounds like it could stall but as soon as I back off the pedal it resumes cruising. just recently installed AC Delco R 45 plugs instead of the cooler Champion RJ12YC plugs I had been running (local driving cooler champion plugs were too rich , new plugs nice tan color). Also I had just flushed cooling system. Dont think these things would cause the bog. Any thoughts how to trouble shoot this?

429bbf:
id try a couple things  first id change the fuel filter and then id test the accelerator pump and see if the cup has swelled up and not pumping fuel . fwiw

Dogmeister:
Check your air valve spring tension. If it's too lose it can cause hesitation. Start with a half turn after the spring contacts the pin. You may need 3/4 - 1 turn. Make sure you tighten the locking screw when you're done.

greggome:
not sure the location of this spring. I see the external spring that attaches to the secondary shaft.  Anyway to check this spring tension without pulling the carb? Carb only has been run for 1000 miles since rebuild. I'm surprised anything like valve spring adjustment or accelerator pump would be out of wack.

Cliff Ruggles:
Most likely the accl pump seal and/or pump has already failed.

Very common problem and EXACTLY why I have much better accl pump seals made as NONE of the "blue" ethanol resistant seals you will find in rebuild kits will last very long in contact with this new fuel.....no matter what they tell you......Cliff

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