Signs and Symptoms of Engines That Flood

by Hans Fredrick
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Flooding is a problem mostly associated with older car engines. Newer cars almost all have a computer-controlled fuel injection system. This ensures that the engine is not flooded with more fuel than it requires in most situations. However, mistakes that cause flooding happen even on those engines occasionally. Look for these telltale signs to help let you know if your engine has flooded.


Normally, when a healthy gas engine is operating, you shouldn't be able to smell gasoline. This is because the fuel system delivers it into the engine at the exact rate that the motor burns the fuel. In a flooded engine, the fuel is coming too fast and isn't being burned. As a result, you will often smell gasoline when you try to start the car and it doesn't start successfully. If you smell gas often when starting, it could be a sign that the engine is prone to flooding.


If you make the mistake of starting your vehicle on a cold day and then turn it off right away, you might find that it won't start so easily the second time. A vehicle that has this specific problem is likely flooding. To help a vehicle start on a cold day, a car sends some extra fuel to the engine to help it get started. If the car isn't allowed to run, that fuel doesn't burn off and just sits there. This makes the mixture too rich when you try to restart the vehicle.


A number of different problems can affect cars on start up, but many of these have slightly different symptoms. When a car doesn't start due to flooding, the motor will continue to turn over but it won't fire up. This is different compared to a dying battery, where you can hear the car losing the energy to turn the motor over. If you suspect flooding is why your car won't start, try leaving it for an hour and attempt to start it again. If the fuel evaporates, you may be able to start the car.

Fouled Plugs

If an engine is flooded severely, it may foul the spark plugs. This means that the ends of the spark plugs get wet due to the excess fuel in the system. When a spark plug is wet, the electrical energy that tries to fire during starting grounds out instead of firing. Sometimes fouled plugs can be cleaned, but more often than not you should replace a spark plug that has fouled due to flooding.

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