Car running WAY too rich

Brother Hesekiel

Brother Hesekiel

Senior Member
My car is running way too rich, always has been, but it may run even richer now with the air cleaner I installed a few weeks ago. I can start the car easily without choke and without raising the idle, and while I don't know what the gas mileage is because I don't have a working odometer (a rebuilt one is on the way to me), it can't be much better than 10, perhaps 12 miles per gallon.

I drive only short distances and the car runs superb, but I know of course that it runs rich. Here's a photo of the spark plugs I pulled today (all 4 looked like this). They are Champions and the gap was about 0.35". I reset it to 0.33" now.

spark-plugs.jpg


I like the idea of having filtered air going into my carburetor. What would you suggest for me to do to solve the problem of running so extremely rich?
 
If you run an air filter you should run a pipe or hose from the carb bowl vent to the inside of the air filter, so they are balanced air pressure.
 
Make sure your float level is set properly, does it drip gas when the engine is not running?
 
besides float level, check to insure the float is not cracked with gasoline inside it by shaking it and listening for liquid in there. A common error on carburetors is to leave one gasket stuck in the bore and place another over the main jet, then installing it with two gaskets, which lowers the jet, enriching the mix. If all this checks out OK, then consider that the jets need to be flow tested and corrected. OR, buy a rebuilt, flow tested carburetor from Berts and be done with it.

here's a page with charts useful in debugging your carburetor
http://modela.org/
 
If we are talking about a Zenith carburetor and If you have the GAV open less than a half turn and you are still running rich, there are two possible reasons. The most probable is that the main, cap, and comp jets are not sized properly. Most reproduction jets are not sized correctly, and many of the originals have been ruined by people pushing welding tip cleaners through them in an effort to clean them. Properly sized jets are a must for good gas mileage.

Another thing to consider, if it is an early Zenith it has a brass screw in GAV valve seat. Check to make sure one is installed if one belongs there. Rebuild kits come with a new comp jet and a new GAV valve seat. They both look almost alike and can be installed in the wrong position. If you have the GAV valve installed in the comp jet position the car will run rich.

Tom Endy
 
Update: played with the carburetor yesterday and couldn't find anything wrong. Moved the GAV sleeve right at the carburetor inlet and was able to close it (clockwise) another 35-or-so degrees until I felt it's set all the way down tight.

Drove the car today and noticed that the GAV knob now sat about 35 degrees to the right, off center. Sure, that's what I did yesterday. Carefully touched it and -- don't know why -- tried to turn it further to the right, and it worked. Turns out I was able to complete a full 360, so I was actually driving with a full turn open all that time. No wonder it was running rich and sucked gas like crazy!

Should be embarrassed about being so stupid, but I'm glad that in this case the solution costs me less than a new carburetor. To my excuse, I know that tight is followed by loose, so I didn't want to use force to turn the adjusting knob, wrongfully assuming it was closed already.
 
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