Flooding on a carbureted engine is done by pumping the gas pedal. True the engine runs on gas but pumping the pedal actuates the accelerator pump in the carburetor. That pump is there for those times when you need extra gas right then. Like pulling out to pass or merging in traffic. When you step on the pedal it dumps a large amount of gas directly into the throat of the carb.
Why the engine doesn't start is a matter of how clean your plugs are. Flooding causes the ends of the spark plugs to become "fowled" and the spark has trouble grounding on the electrode in order to make the necessary spark. The newer the plug the less likely there will be a problem. But like anything, it all depends on how much gas has been pumped into the intake manifold first. A less common reason on carbureted engines is the choke not opening. There are a number of different configurations but the choke flap is closed by some sort of bimetal spring that is temperature sensitive. When the engine is cold the spring tension is pretty stiff. When the engine starts cranking vacuum is produced as long as the engine is healthy. Usually a vacuum break is employed through a series of linkages that eventually pull on the choke flap and make a small opening for air to pass through. The choke changes a typical air fuel mixture of about 15 parts air to 1 part gas into a 8 to 10 parts air to fuel mix. If the choke can't open it changes the mixture dramatically and too much fuel is sucked into the combustion chambers and the plugs are coated. In the old days when the flap wouldn't open, we would stick a screw driver behind the flap forcing it to stay open while the engine was cranked. This would work usually and people hated paying you to start their car when they saw what was done. Now days with the computer controlling so much it's hard to fowl a plug. Maybe Steve can talk more about OBD cars. I know in the 80s there was what was called flood mode which the oxygen sensor decided too much fuel was passing through the system and it shut off the fuel supply. That would happen when someone tried to start a car and if it didn't catch right away they would start pumping the pedal. Isn't necessary in fuel injected cars but you'll never convince the average driver. Hope that isn't too confusing... ----- Original Message ----- From: Victor Gouveia To: Blind Handyman Listserv Sent: Thursday, February 21, 2008 10:55 PM Subject: [BlindHandyMan] Flooding Engines Hi All, Speaking of vapour locks and the like. One question I've always had, and still have to this day is, how the hell does one flood an engine if one pumps the gas too many times before starting it? I mean, doesn't the damn thing run on the stuff, and yet it won't start if you give it too much gas. Wonder if you car guys could explain what flooding the engine is, what it does, why it happens, how one can prevent doing it in the future, and what one can do if you have a flooded engine. In case anyone needs a car to base their instructions on how to start up a flooded engine, we can use my wife's car, a 1986 Honda Accord, four door four cylinder engine, automatic transmission, and no fuel injection. I'm asking this question for two reasons. 1. we actually have a car now that may get flooded at some point in the future, and this is a real concern for me. Granted, I have roadside assistance should we ever have major car trouble, but if there's a real bad storm out there, and the auto service isn't expected to get there for hours, it might be a good idea if, either I or my wife were able to start that car on our own. I'm also thinking about the fact that my wife is often on the road being that she's a nurse doing home visits all the time, and my daughter is always with her on a daily basis, going on shopping trips, going to daycare or school, or just going to church. The thought of my wife being out there alone scares me, and the thought of my wife and 5 year-old daughter being there with her, scares me even more. Any help would be appreciated. Victor Gouveia [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
