Good morning Gentlemen,
Good morning Gentlemen,
I must say that I'm truly impressed with your thought processes expressed thus far. Hindsight is a wonderful thing and I only wish that I excercised the same logic when this problem first occured a few years back.
So, for a moment, let's highlight what we know so far:
-Problem is isolated to one carb
-All three plugs on the affected carb are rich
-Poor idle and low speed engine performance
-Seems "OK" at high engine speeds
-The problem came on suddenly
So, really....only one question remains:
What part of the suspected carb is utilized by all three cylinders and can cause rich running at idle...and poor low speed performance. By looking at the spark plugs, the problem would appear to be more than a simple mixture adjustment could compensate for....Agree?
Let's take a look at the accelerator pump circuit and the related components for its operation. There are three discharge nozzels, three screw-in check valves at the nozzels...and a dual diaphragm accelerator pump assembly which pumps fuel when needed.
Drew suggested that possibly the pump nozzel check valves were loose, hence allowing fuel to drip into the barrels. As these check valves loosen up over time, this certainly would cause the problem...but not this time, as the check valves were indeed tight.
So, what's left?
How does the accelerator pump circuit get its fuel supply? Here in this question lies the answer: In the bottom of one of the float chamber is the "pump discharge check valve" which supplies fuel to the accelerator pump circuit...only when fuel is needed. If this valve were to stick open, fuel would be drawn through the three dischage nozzels, at all times. Hence, at high engine speeds, the excessive richness would be masked by the fuel already passing through the carb.
Here's the culprit:
Hidden in the float chamber:
The "repair" is simple...Remove the check valve and shake. You should hear the check ball rattle. Nope...not this time! Clean valve with carb cleaner and compressed air...shake again.
Rattle...rattle. Reinstall valve, reassemble carb...Problem solved. But, let's take a look at these potential trouble areas, before putting that carb top cover on:
These "screws" which secure the pump discharge nozzels are check valves, as well. Although it is rare that these valves malfunction...they do become loose and allow fuel to seep from under the nozzles.
All back togther now....
Many thanks to all of you for your input...My goal, if you will...was to help up all with that sometimes, ever so challenging, diagnostic steps to determine what's wrong with my car.
Although this problem is pretty unique to the BB, I have other ideas for "quizs" that I'll be posting in the near future. Ideas are welcome...