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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Wardog on February 22, 2011, 09:51:41 pm
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Hello, I have a 78 Blazer, 350 w/auto equipped with a quadrajet. The truck was working great except needing primary shaft bushings on the carb. I had the bushing installed and went ahead and refreshed the carb with a kit; no modifications or changes other than the bushings. The erratic idle and vacuum leak were gone but a new issue has come up. It now wants to fall flat on its face when accelerating, as if it's getting way to much fuel from the accelerator pump. I move the linkage out to the outer hole and it helped out quite a bit but still has the hesitation.
Any ideas or suggestions about what might be causing this?
Thx/Mark
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When you refreshed it, did you rebuild it or just clean it up ? Also did you check your floats for proper operation and that they are not getting stuck ?
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I just had this same problem with mine. It ended up some of the vacuum lines were leaking. Some were going to the wrong places, and also welcome I used to live in Warrington(escambia county). Right down the road.
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Did you replace the accellerator pump seal when you were in there? Have you gone through the step by step process of tuning the carb? Is it only when you kick in the secondaries or under lighter accelleration as well?
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Q-jets are famous for having the back flapper open too fast when you romp on it. It causes too much air to enter the carb. You can adjust this out. There are several threads on here about how to adjust it.
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Thanks all...
I replaced the parts that come in the kit i.e. accelerator pump, check ball, gaskets, etc. All the adjustments according to the procedure for year/model. I double checked all the vacuum lines, there are only a couple of them. Originally everything was working fine except air leak at the primary shaft so the only adjustments I made were to the mixture screws, idle/fast idle. It seems to do this when I accelerate, especially up hill. After a few moments it catches up and runs fine till I need to accelerte again. I sprayed carb cleaner around it while it was running and didn't detect any air leaks. It seems as if when the throttle is opened up lots of fuel is shot into the venturis, not sure what would be normal. Is there different volumes of accelerator pumps?