What does it mean when a carburetor is flooding?

Carburetor flooding is a condition in which an excessive amount of fuel is delivered to the engine, preventing it from starting or running properly. It occurs when the carburetor overflows with fuel, causing the spark plugs to become wet and unable to ignite the fuel mixture. This can be caused by several factors, including a faulty float valve in the carburetor, a clogged air filter, or a malfunctioning fuel pump.

Watch a video of causes of carburetor flooding

https://youtu.be/gO_ceC5Cv6s?si=Up8FjJhMloGCK4E2

Leaking or overweight float

To test your brass or plastic float, heat up water just prior to boiling and immerse the float in the water. The inside of the float will heat up and expand forcing air out of any hole or crack. The smallest hole will show bubbles in the water.

A Nitrophyl float is solid and the only way to test them is to weigh it with a gram scale. Every float has a different weight.

Stuck float

Move the float up and down to feel any catches. The float pin could be worn. Also make sure the float isn’t rubbing on the side of the float bowl. The Autolite 4300 and Rochester Monojet is especially guilty of this happening because the float fills up the float bowl so much.

Dirt in the needle and seat

What happens often is you clean your carburetor, then start the engine. Dirt from a dirty gas tank, or in the fuel line rushes up and into the carburetor. So if your gas tank has been is use for many years, consider taking it off and giving it a good cleaning. Most rebuilds that are returned as defective are found to have dirt in the bottom of the float bowl. Eastwood has a good tank cleaner and sealer.

Note: Even with a fuel filter you can get dirt up to the carburetor. Filters can’t be so restrictive that they cut off the gas supply.

Another thing to think about when it come to the needle & seat. Any pressure on the needle (viton tip) while adjusting the float can damage the tip and gas can leak by the needle.

Make sure all of the old gasket has been removed under the seat.

Over pressurized fuel pump

The fuel pump is another possibility. If you have an electric pump be sure to have a regulator installed between the pump and the carburetor. Set it for 4-5 lbs as per your motors manual. Carter WCFB can be at 3 lbs.

New fuel pumps are especially suspect. It isn’t unusual to have them pumping at 20 lbs of pressure.

Old gas has turned to varnish

Has your vehicle been sitting for 3 or more months? The gas may have turned and coated the inside of the carburetor. You will usually smell varnish when this happens. We recommend you use Ethanol Defense in all of your engines. This will help keep ethanol from damaging your parts.

How Do You Start A Car That Was Flooding?

To start a flooded engine, follow these steps:

1. Wait: Wait a few minutes to let the excessive fuel evaporate from the engine.
2. Depress the accelerator pedal: Push down the accelerator pedal all the way to the floor and then release it. This helps to clear the excess fuel from the carburetor.
3. Crank the engine: Turn the key to the "start" position and crank the engine for a few seconds. Do not hold the key in the "start" position for more than 5 seconds, as this can overheat the starter motor.
4. Repeat steps 2 and 3: Repeat steps 2 and 3 a few times until the engine starts.
5. Warm up the engine: Once the engine starts, let it warm up for a minute or two to help evaporate any remaining fuel in the carburetor.