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Why Does My Car Smell Like Petrol?

Smelling raw petrol coming from your car is obviously quite concerning no matter who you are and can really be a serious problem. However, there’s a couple of things you should think about before talking to a mechanic about it and with our recent focus on fuel related topics, we thought we'd cover this common concern. Modern cars are all run through computers, a topic we've covered a few times here, here and even here. However, ask anyone over the age of 45 and they’ll tell you that old cars used to always smell fuel-y.

In old cars, this was a side effect of 2 functions. Firstly, carburettors, a yé olden system of fuel delivery, which were never able to perfectly suit every driving situation and secondly, the need to choke the carburettor to start the car.

While this sounds like a bad joke, choking the carburettor was a genuine term and describes the function used to supply extra fuel to the engine to help cars start and warm up more efficiently from cold (basically from room temperature).

Another thing of note with carburettors was the inability to be tuned for every situation. As carburettors were set-up only when the car visited the mechanic and relied on a consistent flow of air of similar density and temperature through them to meter the fuel, they were often sensitive to falling out of tune. For example, if you were to change altitude compared to where your car was tuned for, you would run richer or leaner and lose power and the car could start to smell fuel-y.

Unsurprisingly, with the rise of the computer era, EFI (electronic fuel injection) and Volvo’s invention of the Lambda sensor in the late 80’s, the switch over from carburettors to EFI was fairly quick.

With the introduction of EFI and the Lambda sensor as cars were suddenly able to monitor the efficiency of the fuel burn through the exhaust and readjust based on the conditions meaning more consistent power and less fuel smells. This is good news however, the historic legacy of the choke has somehow lived on.

Though you might not know it, engines have (overall) changed surprisingly little over the last 100 years and the use of extra fuel to both start and help warm up the car is still prevalent. This ‘cold start' map (a term used to describe how much fuel is injected based on air intake) makes the car burn extra fuel and can cause the same nostalgic stench of half burnt fuel. With that said, this should end after around 5 minutes of driving.

However, if your car is constantly smelling of raw fuel though, we would still recommend talking to our Kashy mechanics.

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