Petrol engine flooded?

What does it mean when your engine is flooded, and what can you do about it?

Engine flooding is a common cause of breakdowns, especially on cool or colder days when the engine needs more fuel to run smoothly until it's warmed up.

If you can't start your car, this could be the problem. Read on to find out what causes a flooded engine and how to fix it.

Car engine

What causes a flooded engine?

A petrol engine floods with fuel when it’s switched off too soon after being started from cold. After switching off, the unburned fuel remains in the engine, wetting the spark plugs and making the car difficult to re-start.

It often happens when a car’s moved out of a garage onto the drive or moved a short distance to let someone else out. It’s most common in the spring and autumn.

Some engines are more susceptible than others. It’s most likely with small, four-cylinder engines but can happen to any petrol engine in the right conditions.

How can I avoid flooding the engine?

It’s best to always allow your petrol engine to warm up once it’s been started from cold. This only takes a few minutes – it’s warm enough once the engine note changes and the idle speed drops slightly. You’ll also see the temperature gauge move off the minimum.

How can I tell if my engine's flooded?

Symptoms of a flooded engine include:

  • Very fast cranking (the engine sounds different when you turn the key – usually a 'whirring' sound)
  • A noticeable smell of petrol, especially around the exhaust
  • The car doesn’t start, or starts briefly and cuts out again

How can I fix a flooded engine?

Before you start, it's a good idea to close any doors and windows to your house. That's because the exhaust is likely to smoke excessively for a few seconds when the engine starts. If the car is in a garage, make sure the garage door is open and there is plenty of ventilation.

To clear the excess fuel:

  1. Crank the engine with the accelerator pedal pushed to the floor.
  2. Continue cranking the engine (for up to 10 seconds) until you hear the engine trying to start.
  3. Once the engine’s started, allow it to rev up for a second or two, then hold it at a higher than normal idle speed for a few more seconds
  4. If the engine doesn’t start within 10 seconds there may be other issues and you should switch off and call us for assistance.
  5. Once the engine’s warmed up, you can switch off safely or use the car normally.

(2 October 2019)

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