Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

fuel consumption issue.

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Ligfishing:
Very strange situation. I finally got some time to do some adjustments. Armed with having read Cliff's book cover to cover twice, I decided to see if my idle mix could be improved. I have a good functioning engine but I thought i could do better since it seems  to burn twice as much fuel at idle as the other engine in my boat. fuel management gauge says starboard engine is burning 1.7-2.0 gallons an hour at idle. Port engine starts out at nearly 4 and gets down to 3.5 once warmed.

So i moved both idle screw all the way in and started to turn them out. once i got to three complete turns and no effect what so ever. I'm assuming i massive air leak somewhere. I could not get the fuel use down and the idle is smooth but maxed out at 650 rpm, the lowest it would go. so throttle closed 100% and screws closed 650 was the limit.

Is my assessment correct about the air leak? I should have been able to starve the engine to a stall by cutting off the air?

as to why shes gulping fuel? nozzle drip?

as soon as i go to an off idle throttle position the fuel use comes down dramatically. which is strange to run harder and use LESS fuel...

once off idle the numbers match the other engine.

I'm about to reassemble a fresh carb to swap out.
(using Cliffs parts) I will report back.

Greg-

Cliff Ruggles:
Idle tubes may be plugged up, common problem with Marine carburetors......Cliff

Ligfishing:
Thank Cliff, I did the re assembly of the first rebuild and I will mount it up and test tonight.

would clogged idle tubes cause the high fuel burn ?

Also Whats your recommendation as to a cleaning( soaking) solution?

Greg-

Ligfishing:
OK fresh rebuilt carb installed no problems, but  now idle wont come below 1000 rpm. air leak or float set too high....
took air horn off everything looks good. throttle plates 100% closed.

Ligfishing:
Forgot to add the engine has a 13 degree tilt ( common for marine application, however it has a wedge plate to compensate, still has about 8 degrees back tilt? do it adjust for this in the float level?

issue is definitely limited to the carb, as re installing the old the  idle returns to normal. ( no external vacuum leaks)

gotta be the float height?

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