How Does a Carburetor Work?

Carburetors in old cars are mechanical devices that mix air and fuel for combustion using the Bernoulli principle (venturi effect), primarily used before fuel injection became standard in the late 1980s. They use a float chamber, jets, and a throttle to manage the fuel-air mixture, often requiring manual or automatic chokes for cold starts .

For a simple picture, a carburetor is a device that is fitted above an engine’s cylinders and has both an air and fuel pipe attached to it. A vacuum gets created, which is what the carburetor relies on to help draw air and fuel into the cylinders.

When air gets pushed down the pipe, it passes through a narrow opening known as a venturi. The air must speed up to pass through this area, which causes a drop in pressure. It’s this pressure that allows air to be drawn in through the fuel pipe.

Below and above the venturi are two valves that are important for adjusting the air-fuel mixture. The top of the carburetor features the choke, which regulates how much air is coming into the pipe. The second valve below the venturi is called the throttle, which can open and close to allow different amounts of air to enter the engine.

A throttle that’s more open will allow an increased amount of air to flow through the carburetor, which will bring in more fuel. This allows an engine to release more energy and have more power.

Inside the carburetor there’s a part known as the jet, which is an opening that allows fuel from the float chamber to mix with air before it enters an engine’s cylinders. Float chambers hold a small amount of fuel in them and allow it to flow to the jet as needed.