How does a fuel injected engine flooded

More than a few consumers believe with the advent of modern fuel injection, flooding an engine with excess fuel during a cold start became a thing of the past. How wrong they are: Fuel injectors are capable of pumping more excess fuel than any old carbureted engine ever thought of. And if you’re not careful, all the excess gasoline can bite you and your wallet hard if don’t respect what it can do.

Years ago, when a carbureted engine failed to start on a cold or damp morning, excess fuel merely dripped into the intake and cylinders. Fast forward to today’s engines and injectors can power-spray fuel in to each cylinder individually, adding far more volume than a carburetor ever could. When you’re cranking over an engine that’s not firing up but that has a working fuel system, never stay on the ignition key for more than a few seconds. But how can you tell if an engine’s flooded?

Well, before cranking the battery dead or filling the oil pan with fuel, pop the hood, lean towards the engine and take a good whiff. If you get any type of fuel smell, chances are the engine’s flooded. Then, pull the dipstick and give it the same sniff test. If you get a strong smell here, you probably have enough raw gasoline in the oil pan to damage the engine if it does start.

Now, let the engine sit a few minutes and check the exact oil level. If it’s higher than usual or well over the full mark, you’ve got enough fuel in there to quickly ruin some bearings if you manage to get it started. In cases like these, your only option is to drain the oil/gas mixture and refill it with fresh oil.

If you haven’t managed to over contaminate the oil with fuel, it will take some time to dry out the spark plugs before trying to restart the engine — which could take hours if it’s cold outside. While you’re waiting, you can plug in a block heater if your vehicle has one, recharge the battery, call a tow truck, or hope for a sudden warm-up.

Another risk is igniting any excess fuel that may have found its way into the oil pan. It isn’t common, but it does happen and usually occurs during a backfire, when fuel explodes in a cylinder at the wrong time due to an ignition fault.

You may wonder how any spark up high in a cylinder can ignite fuel down low in the oil pan, but when a flooded engine is turning over, gasoline fumes can move higher where an errant spark will set things off. This almost always results in a damaged oil pan.

Best tip for last: If you’re trying to clear out excess fuel from the intake without taking things apart, crank the engine for a few seconds with the gas pedal fully depressed. All fuel-injected engines will shut off their injectors when cranking at full throttle, but ensure the pedal is all the way to the floor and not caught up on some thick floor mats.

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