How to start a car with a flooded engine

If you can’t get your car to start and you notice that it’s cranking very quickly when you turn the key, a flooded engine could be to blame. This is particularly likely on a cold day when the engine requires more fuel to run smoothly while it warms up.

Find out what it means when your engine floods, what causes it to happen and how you can fix it in this guide.

Contents

What is a flooded engine?

What causes a car engine to flood?

What are the signs of a flooded engine?

Will a flooded engine fix itself?

Can you fix a flooded car engine?

How to avoid flooding the engine

Can you flood a diesel engine?

What is a flooded engine?

A flooded engine is an internal combustion engine (ICE) that has been flooded with too much fuel and can’t, as a result, be ignited.

What causes a car engine to flood?

Petrol engines often flood when they are switched off too soon after starting during cold weather. When the car is switched off, the unburnt fuel remains in the engine, wetting the spark plugs and making it difficult to start again.

This can also result in something called “bore wash”, which is when the fuel removes the oil around the cylinder’s piston rings. 

Vehicles with small, four-cylinder engines are most susceptible to engine flooding, but it can happen to any petrol car.

What are the signs of a flooded engine?

Fortunately, it’s fairly easy to tell if your engine has been flooded. Here’s what to look out for:

• A strong smell of petrol, usually near the exhaust

• Black smoke coming from the exhaust

• Your engine won’t start, or starts and quickly dies

• Fast cranking/a whirring sound when you turn the key in the ignition

However, these symptoms could indicate other issues that are more serious than simply a flooded engine. If you are unsuccessful in starting your car by following the advice in this guide, the next step is to contact a mechanic.

Will a flooded engine fix itself?

Unfortunately, a flooded engine won’t fix itself, but the process of getting it working again is usually fairly simple.

Can you fix a flooded car engine?

Providing there isn’t a fault that’s causing the engine to flood, you should be able to get it working again in a few simple steps. To do so, you need to balance the air-to-fuel ratio.

First of all, open the bonnet and wait for the excess fuel to evaporate (probably about twenty minutes). After you’ve done that, follow these steps to get your car started:

• Crank the engine, keeping the accelerator pedal pushed to the floor

• Continue cranking for up to ten seconds until you hear the engine try to start

• Once it has started, allow it to rev for a second or two, then hold it at a high idle speed for a few seconds

• After ten seconds or so, if the engine still hasn’t started it’s likely there’s a more serious issue at play. Take your car to a local mechanic who will be able to tell you exactly what’s going wrong and how to fix it.

How to avoid flooding the engine

The best way to prevent your engine from flooding is to allow your car to warm up properly when you’re starting it in the cold. It should take a few minutes at most; just wait until the idle speed drops and the sound of the engine changes.

Can you flood a diesel engine?

Diesel engines can’t be flooded because they are built differently. 

If your car still won't start after following the advice in this guide, there could be a more serious problem with the engine, so it's best to take your car to a garage to have it looked at by a professional.

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