Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

fuel consumption issue.

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Cliff Ruggles:
Float level would not cause high idle speed.  If the float is incorrectly set, it can effect metering or calibration.  Too high for sure and it will cause flooding, but set anywhere in between completely on the bottom of the bowl to just below the gasket surface it will NOT effect idle speed dramatically. 

Loss of control of idle speed means that you are getting air into the engine from someplace at or below the carburetor throttle plates (vacuum leak). 

I see this a lot.  It can come from using the incorrect gaskets under the carb, or between the main casting and baseplate.

Usually it is a problem with the throttle plates not being fully seated when closed, or incorrectly centered and indexed.  I see this problem with twisted throttle shafts as well, especially the primary shaft when folks remove the fast idle parts without holding them and twist the shaft in the process of removing the retaining screw.......Cliff

Ligfishing:
Cliff:
Rebuilt second carb and no problems with idle speed.
Idle mix screws now have an effect and all seems good. However my original issue still presents itself.

Using 4.0 gal per hour at idle 650 rpm and as soon as I touch throttles drops to 2.0 at 900 rpm

And if I shift into gear it also drops to less than 2.0 gph

My starboard doesn't do any such thing.

Ideas???

Cliff Ruggles:
Are  both carburetors exact "blueprints" of each other in every respect?  What I mean is same part number, and everything from idle tubes, airbleeds, jets, metering rods, and internal parts the same with the same settings?

If they are, swap them from one engine to the other and see if the problem follows the carburetor in question.....Cliff

Ligfishing:
Yes they are but I think I've found the issue.

Seems I trusted the flow sensors too much.
I switched the flow sensors and the problem seemed to follow the sensor.
I've ordered a replacement and  will install later this week.

I should have  tried to remove the senors from the diagnostic flow.

Plus a mechanic buddy said  if one motor was processing that much more fuel at idle you would not have a very good running engine, there would be some other by-product. Both engines run equally smooth at exactly the same rpm( verified  with laser tach).

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