Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: defiant1 on June 19, 2014, 10:57:53 AM
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I have 7042250 quadrajet on my '70 Olds 350. Upon acceleration is overflows gas out the air horn gasket and the opening the accelerator pump shaft extends out of. It leaks a fair amount of gas that after ten miles I had over 8 ounces of gas resting in the voids of my intake manifold on the drivers side.
So, I checked/replaced all of the following:
Float: Set it a correct height as well as lowered it and still had same result. Used a new float as well.
Accelerator pump
Needle and Seat: Vacuum tested the original and replacements. Seat threads not cross threaded.
Check ball- Used old check ball to seat area for new check ball to reside
Mechanical Fuel pump is pushing fuel between 6/6.5 PSI
So not sure what else it could be. Gas is not coming out of the primary areas, just around the accelerator pump shaft and wicking through the air horn gasket.
d1
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call Cliff and get a thick top gasket and(if you don't have one already) one of his super alchohol resistant accelerator pumps. your casting may be a bit warped so the thick gasket should help. If not, you need the casting "unwarped" (this would be the first thing that comes to mind) so just check and see if this could be the problem.
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Pressure test the gasket under the fuel inlet seat. A tiny leak at that location will cause minor flooding.
Install the fuel inlet seat, gasket and needle. Fill the bowl with a soap/water mix higher than the gasket level. Firmly hold the needle down into the seat, and apply some compressed air into the fuel filter housing or inlet. A tiny stream of bubbles will appear if you have a leak.
This is a pretty common problem, we see a LOT of carbs come in here freshly "rebuilt", but leaking under the seat at the gasket due to not clean enough, or minor damage to the seating surface.....Cliff
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Cliff,
I pressure tested the gasket per your instructions, however there was no leaking of air witnessed. In my mind I am leaning towards too high of fuel pressure or the float pin is not being held securely allowing the float to release pressure off the needle directly allowing more gas in the fuel bowl.
At this point, I am grasping at straws...
d1
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Those carburetors are more "touchy" with high fuel pressure than the later designs, but still fine to 6.5psi with a .135" inlet seat. I've built and tested many of them and zero issues with those specs.....Cliff