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
Very dangerous because so many engines and cars burn up because of a gas leak, or flooding. All the gas has to do is touch a spark and off it goes.
Which reminds me, anytime you are working on your engine be sure to have a fire extinguisher close by.
A story about that.
A customer spent years restoring his GTO and the 1st time he took it out for a trial spin, the carburetor flooded over and caught fire. Well, guess what? He didn’t have a fire extinguisher, or anything else to put the fire out. He had to stand there and watch his car burn. It made me sick just hearing about it.
When I talked to this customer he was just getting done with the 2nd restoration and was calling me for a carburetor kit. The carburetor was the last thing he had to finish the car.
Back to flooding
There are several things that can cause flooding. I will address each.
The 1st thing most people want to do when their carb is flooding is change the float setting. Unless the float is hugely off, that isn’t the problem. At least as far as the setting goes. Set your float to specifications and leave it there. Fudging the float setting is covering up the real problem.
Now the float could be causing the flooding. It might have a hole, or crack allowing it to fill up with gas. That makes it too heavy and will keep the needle open.
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.
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.
The most common cause of flooding is dirt in the needle & 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.