Autolite 4100 Flooding

Here are key factors that can cause a 4100 4 barrel carburetor to flood, along with a checklist of what to inspect:

• Damaged Needle: Any pressure on the Viton tip can damage the needle.
• Dirt in the Needle & Seat: Debris from the gas tank can cause issues even after a good rebuild. Fuel filters may not catch all particles. Try blowing air into the inlet to clear any dirt. Persistent problems may indicate a need to clean the gas tank.
• Float Leak Test: Heat water just before boiling and submerge the float. If the float has a leak, expanding air will bubble out.
• Float Level: Set according to the instruction sheet. Do not adjust the float to correct richness, as it masks the actual problem.
• Float Clip: Ensure the clip that snaps onto the float pin and fits over the seat is in place. A missing or incorrect clip can cause excessive fuel entry.
• Float Movement: Check if the float is catching when moving up and down.
• Fuel Pump Pressure: Ensure the pressure is 4 - 4.5 lbs. If necessary, add a regulator between the fuel pump and carburetor. New fuel pumps can be unreliable.
• Carburetor Warpage: The 4100 carburetor is prone to warpage, which can cause fuel to spill into the bore, especially on inclines. Use flat stock to check for warpage and consider adding a second float bowl gasket without any sealer.
• Extra Gasket Material: Check for extra gasket material under the seat, as fuel may leak past the threads.
• Ruptured Power Valve: A damaged power valve can lead to a rich condition. Use a vacuum tester or blow through it to check for leaks.
• Main Discharge Leakage: If fuel dribbles out of the main discharge at idle or when the engine is turned off, the discharge may be leaking. Test the discharge for leaks.

• Might be pressure build up. Before turning off release the gas cap. If the flooding persists then it isn't the back pressure
• Most likely it is the needle & seat. Needle isn't sealing, or viton tip damaged.