Engine flooding has nothing to do with water. It’s a phenomenon that happens to gasoline (petrol) engines when they have too much fuel and not enough air. A flooded engine is hard to start. If your engine floods with the car already running, chances are it will stall.
Starting or running becomes impossible because the fuel splashes on the sparkplugs, making them less efficient at sparking. If the flooding is not severe, the fuel-air mixture won’t be right for perfect combustion.
How to Start a Flooded Engine
In most cases, you don’t have to call in a mechanic or have your car towed when it’s flooded. You can easily unflood it and get it working again.
You have a couple of options. Choose one depending on how applicable it is.
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Wait it Out
If you have time, pop the hood and let the car sit for an hour or two – especially if it’s sunny and hot. Petrol is very volatile. The surplus fuel in your cylinders will naturally evaporate over time.
With the right conditions, your engine will joyfully startup after an hour of drying. You might have to crank the engine for longer before it kicks on. Don’t be afraid to crank for more seconds, especially if the engine gives signs of turning over.
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Press the Gas Pedal to the Floor and Crank the Engine
Another approach to the problem is introducing as much air as possible into the ignition chambers. You do this by pressing the gas pedal to the floor as you crank the engine.
Even though it’s called a gas pedal, it doesn’t directly affect how much fuel gets into your cylinders – at least not in gasoline cars. The throttle pedal controls how much air gets into your engine by controlling the throttle body butterfly.
Opening it fully when cranking your car will let it suck in more air, creating a better air-fuel mixture.
You will still have to crank the car longer than usual before it turns over (crank in bursts of up to 10 seconds). Once it does, ease off the throttle but keep the revs high (say 2000) for a while to let the car burn off the excess fuel.
Pro Tip: If it doesn’t work on the first attempt, try the entire procedure again. Keep the throttle open for a bit longer, though, before attempting to start the car.
After that, keep the car running until it heats up or take it for a 30 minutes drive to ensure that the flooding is gone.
If your car doesn’t turn on after trying the above two tricks, you can either wait it out for longer or call in a mechanic. Follow-up repair needs some technical know-how.
Why Is My Engine Flooding?
While flooding is not common in ECU and fuel-injected engines, it can still occur at times. Here are the top reasons why your petrol engine might be flooded.
Frequent Starts and Stops that Don’t Warm Up the Engine
Starting and moving your car for very short intervals then switching it off before it warms up could initiate flooding.
Most engines will run on an open-loop when they are cold. This holds the engine at a higher RPM and lets it consume more fuel to reach operating temperatures that are easier to control faster.
Switching the car off before this happens will let the cylinders lie with more than usual fuel in them. If done repeatedly, it could lead to flooding.
You can avoid this by letting your car sit idling until it warms up if you didn’t intend to use it. If you were going for a drive, start slowly and pick up speed once the car warms up.
Pro Tip: Fuel-injected engine warm-up better when driving. Taking it for a drive is better than idling. Remember to ease into it. Don’t downright floor a cold engine.
You’ll know your car is warm once the temperature gauge moves from cold to the normal position (1/4 way or 1/2 way to overheating mark.) If the car is idling, the RPM will drop to the normally smooth, steady putter.
Some cars have a light that turns green when the engine is up to operating temperature.
Pro Tip: A flooded car will run fine once you unflood it. If the scenario keeps recurring, you need the car checked. There could be a problem causing it to flood.
Faulty or Worn out Spark Plugs
Spark plugs in a gasoline engine are kings of the show. They produce the spark needed to ignite the fuel.
If they are faulty, your engine will misfire terribly. If you keep it running, it will end up flooding since it won’t be burning all the fuel it receives.
While your fuel injection system might compensate for this, your chances of turning off the car with too much fuel in the combustion chambers are high.
If it’s the spark plugs, chances you will get a Check Engine Light (MIL) and a misfire error code when you use a scanner to pull up the error.
A Problem in the Fuel Injection System
A problem with your fuel injection system, especially the fuel injectors, could flood your car. Even though fuel injectors are versatile, they get worn out over time.
Once they fail, they will start injecting a stream of fuel instead of a fine mist. The steady stream will soon be too much for the cylinders hence flooding them.
Moreover, the fuel stream easily splashes on sparkplugs compared to a mist. Either way, they will have a hard time creating the spark needed to ignite the fuel.
A Poorly Adjusted Carburetor
Just as fuel injected cars flood when injectors are damaged, a carburetor-based engine will flood if the carburetor is out of tune or damaged.
In such a setting, the carburetor lets in more fuel than air. Since most carb engines don’t have intelligent fuel-air mixture systems, the extra fuel will soon flood the engine – especially if it’s running at low RPM.
A Rich Air to Fuel Ratio
So far, we’ve realized that a rich air to fuel ratio can cause flooding. This is diagnosis enough for a carb driven engine.
However, if you have a fuel injected car, it could be more than your fuel injectors that are the problem. It could be any of the many components that control your air-fuel mix. These include:
- Oxygen sensors
- MAF sensors
- The ECU
Flooded Engine Signs and Symptoms
Sometimes it’s hard to pinpoint the problem in your engine to flooding. Here is a couple of signs to be on the lookout for.
Darker Smoke for the Exhaust Pipe
Flooded cars start by running very rich. A hard-to-miss sign of a rich engine is a lot of dark smoke from the exhaust pipe.
It would be best if you always had your engine looked over when it gets smokey. Smoke is not common in modern cars – especially now that they are fitted with catalytic converters.
A Gas Odor from the Engine
A flooded engine has more than usual fuel sitting in the combustion chambers. Chances are you will get a stronger than usual petrol stench once you pop the hood.
This smell is gas evaporating. This is what makes popping the hood and letting the car sit a viable way to fix a flooded engine.
Trouble Starting the Car
The last sign that your car is flooded is when it has trouble starting. Your car will crank just fine. However, the engine won’t start. Sometimes, it will try starting and fail or run for a while before going off.
While this could mean many things, the first culprit is flooding. Going through the throttle clearing procedure could help you fix the problem.
If it doesn’t, then perhaps you have bigger problems than a flooded engine.
Can You Flood a Fuel Injected Engine?
Yes. Fuel-injected cars can flood. Even though the fuel-injected system is intelligent and only gives the engine so much fuel, it can go wrong at times.
The failure could be because you often run your car for short distances and turn it off before it warms up. It lets the engine run on a closed loop or one or more sensors in the fuel delivery system malfunction.
What Does a Flooded Engine Sound Like?
A flooded engine sounds like it’s trying to start. It sounds like the first few seconds of turning on a healthy engine. However, a flooded engine will keep cranking and cranking.
The cranking is normally fast – actually faster than usual. It will produce a whine over the starter motor noise. The engine cranks faster because compression is probably lower than it should be due to the flooding.
Can a Flooded Engine Trigger a Check Engine Light?
Flooded engines could trigger a check engine light – especially if it’s a partial flood. By partial flood, I mean only a couple of cylinders are flooded to the extent they can’t fire.
As long as the other cylinders are firing and the engine runs, it will interpret this as a misfire and report a misfire error.
However, with the other cylinders burning and turning the engine, the excess fuel should burn up very fast, sometimes too fast for you to notice.
Can You Flood a Diesel Engine?
No. Diesels are immune to flooding because they work differently from petrol engines.
A diesel engine relies on compression to ignite fuel. It will almost always achieve compression and ignition regardless of how rich the air-fuel mixture might be.
Moreover, diesel engines don’t have sparkplugs. This means that there is nothing at risk when more than usual fuel streams into the combustion cylinders.
Check this too: Signs That You Have a Bad or a Failing Throttle Body
Will Flooding an Engine Damage It?
Flooding an engine is rarely dangerous. Sometimes, it could make your sparkplugs wear out faster, but that all.
This doesn’t mean that you should ignore an engine that floods often. Frequent flooding could mean that something is wrong with your fuel delivery system or combustion system.
Get a mechanic to look into your car and pinpoint what is causing the frequent fuel flooding.
Moreover, an engine that floods because it’s running too rich burns more fuel. It also produces more smoke and pollutes the environment more.
You will lose money at the pump and might not pass a smog test if you ignore the problem and keep driving.