Hi guys, So i have a 79 f150 with a 400. Just a standard motorcraft 2 barrel that came stock. Well whats kinda weird is when i turn it off and wait longer than 30 seconds, it floods. Now when i do it with the air cleaner off, it steams coming out of the carb. Almost like there is condensation on the butterfly and inside the carb and it drips down into the intake. But if i turn it off for maybe 5 seconds, it will fire right back up smooth. Also if its long enough to let that fuel evaporate, it fires quick and smooth. Any ideas? Thanks in advanced.

 

It's typically called "flooding" or a "flooded condition". Meaning there is excess fuel (a liquid) compared to the volume of air (a gas). Referred to as an air-fuel mixture or simpley "AF". The theoretical ideal mixture is called "stoichiometric" ratio which is 14.7:1

The carburetor is one of the main parts of a vehicle. Its job is to regulate the speed of the engine. It does this by measuring the amount of air necessary for the speed at which you wish to travel: it pulls a small amount of air and fuel for low speeds, increasing that amount as you speed up. A flooding carburetor can lead to serious problems, but you can prevent the problem by learning about some of its potential causes.

Excessive Fuel Pressure
A normal fuel pressure is 6.5 lbs. per square inch. High fuel pressure--usually due to a fuel pump that's defective or worn--can cause carburetor flooding. Check the fuel pump, or if you lack the expertise to do it yourself, seek a professional opinion.

Defective Float
According to the pmocarb.com, the defective float problem develops when the tang (the metal adjustment on the float) is too long and catches on the webbing part that supports the stanchions on the float pin. To solve the problem, shorten the tang, then readjust the float drop.

You will occasionally need to replace the floats on the carburetor. After making such a replacement, compare the old floats to the new ones. Make sure that the pontoons--the parts of the float that actually float in the liquid--are in right relation to the hinges so as to reduce the level of friction with the float chambers.

Dripping
If the engine is shut off and the fuel is dripping down the carburetor, it could be because the fuel line is too close to a radiator hose, an exhaust manifold or another source of heat, or internal debris which is preventing fuel shut-off, or defective carburetor. The heat causes the fuel--a liquid--to expand past the needle and the seat or there is trash on the seat which results in flooding.

Rebuild the carb for about $25.

 

The carb and fuel pump aren't even 2 months old. So im pretty sure there isn't anything wrong there but the fuel line could possibly be close to the headers or radiator hose. Any other ideas?

 

I'd be looking hard at the float adjustment and if the needle valve has a little trash stuck in it. I might even run the thing with the carb top off to see what's going on. This is an accepted method as that's how the float level is supposed to be adjusted. I keep a big fire extinguisher at the ready when I do this.

Chris

 

It pays to be absolutely certain in these circumstances; don't rule it out until you are. Makes the troubleshooting process a lot more effective.

 

Given the "quality" of new parts now a days it is always best to back track when something goes wrong. It took me 3 attempts to replace a pick-up coil in distributor last year. After the second failed part I switched parts stores and brands.