Carter AFB Flooding Problem

posted in: carburetor, Carburetor Kit, Carter | 9

Gas is leaking out of the main throttle shaft, or gas is coming out of the top vents, or you get black smoke while idling. All of these are indications of too much gas, or flooding.

Here is a list of possible causes in no order of importance.

afb needle & seat
Most float valves (needle) have a black Viton rubber tip on the end. The Viton tip needle may have been damaged when installing. Be sure not to put pressure on the needle when adjusting the float. A damaged Viton tip will allow too much fuel to enter the float bowl. Sometimes wiping off the Viton with mineral spirits to take any residue off will help.
Did you forget the gasket that goes behind the seat. Also make sure the old gasket was completely removed. See #22 in the illustration.
Check for cracks around the seat area. This would allow the fuel to bypass the needle & seat, so the fuel would never get shut off.
The float may be leaking causing it to sink. Heat up some water just prior to boiling and immerse the float. There should be no bubbles.
Gently move the float up and down. You should not feel any resistance or catching. A worn float pin, or improper installation of the float might cause this. If there is a metal clip that attaches the float to the needle, be sure it pulls the needle straight out. Move the clip around until it does. The float could be pulling the needle at an angle and it might cause it not to seal.

Check the venturi gasketmain discharges to make sure they are sitting flat and there there is no old gasket residue left under the new gaskets. See number 32 in the illustration.

Ethanol will leave residue behind and the small orifices of the venturi are subject to clogging. Use thin wire to clean out the small passages. In the past we would have said not to do this because you might make the openings bigger. This is still a possibility, but there isn’t any other way to get the passage cleaned. Carburetor cleaner and air pressure will not remove ethanol residue, so the wire is necessary. Just be careful not to enlarge the openings.

The fuel pump could be putting out too much pressure. New pumps are especially suspect. Test your fuel pump and compare with the specification in your motors manual. It would be somewhere between 4 & 7.

That should cover most problems.

If you had an experience with a flooding carburetor, it would be nice to hear what your solution was.




9 Responses

  1. I have a new 4bbl Carter AFB on my 402 Chev 1972 Chevelle. It was running fine last summer when I got it. Now it starts right up as usual, after warming it kills at stops doesn’t want to idle. What happen? How do I fix this. I never touched it, it was set up nicely when I got it. I struggle to keep it running at stops.
    Any advice would be wonderful.

    David J.

    • A guess would be that there is too much fuel at idle and it’s flooding out at stops. Does it smell gassy when that happens?

      Sitting around is very hard on carburetors due to the lousy gas and ethanol that we have. Float needle may be damaged from the ethanol. The idle vents may be plugged with residue. Some AFBs had vent holes drilled in the body next to the idle mixture screws. Make sure these are open. Make sure the fuel bowl vents are open.

      If any of these things turn out to be plugged then a cleaning of the carburetor is in order.

      • David J.

        It does not smell gassy at stops, strongly wants to die. I must have let it set to much.
        What is the time for a cleaning?

        • You need to pick up a gallon of carburetor dip from the parts store, clean the carburetor, then install the new kit.

  2. what is the part number or name of #23 on the diagram below. I cannot find it anywhere?

  3. Angelo Morello

    Hi Mike
    I have 68 mustang with a 302 windsor running a Carter AFB c2 9627s carby
    Its running lean and has a flat spot when you stand on the pedal.
    Can you tell me what needles, jets and springs numbers I need to fix this problem ??
    Any information would be appreciateted.

  4. I just got a 1982 ford f 150 with the 4.9 6 cylinder and belive it has the carter carburetor on it and while it is running black smoke comes from the tail pipe and can smell gas real strong so that it will burn your eyes. can you email me a manual for that year and it is a long wheel base and 4 wheel drive, thanks for your time.

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