What does a carburetor do?

The carburetor is an essential mechanical component of the engine, providing the air/fuel mixture necessary for combustion. Although this component has not been used in automobiles since 1993, it is still very common in motorcycles and some very old vehicles.

What is a carburetor?

The carburetor is a mechanical component of a car engine. Its role is to ensure the perfect mixture of air and fuel so that the latter burns to power your vehicle. For this reason, it is not found in diesel cars, but only in gasoline engines. The first carburetor was developed in 1886 by the founder of Mercedes-Benz.

The carburetor was then replaced by an injection system with an injection pump, similar to that found in diesel engines. But older cars are still equipped with carburetors.

Today, it's almost impossible to find carburetors on a car unless it's a very old model made before 1993. On the other hand, carburetors are still found in engines such as light aircraft, motorcycles, chainsaws, lawnmowers, boilers, and so on.

The number of carburetors in your car depends on the number of cylinders: if your engine has 2 cylinders, there will be 2 carburetors.

The basic carburetor consists of

The constant level bowl

in which a needle-equipped float opens or closes the fuel inlet port. This system eliminates the effects of level differences between the tank and the carburetor.

The position of the float is generally adjustable: choosing the right level prevents the engine from "drowning" and avoids "holes" in operation caused by too high or too low a level.

The diffuser

Or the nozzle, which has a throttle and is generally in the form of a Venturi tube. It creates the vacuum necessary to draw in the fuel. The shape of the throttled part of the diffuser is carefully designed to avoid turbulence in the air column that would impede fuel intake.

The maximum velocity at the throttle must be within specified limits (generally between 100 and 130 m/s). Complete vaporization of the mixture takes place downstream of the diffuser up to the inlet valve.

The nozzle

The nozzle is located at a slightly higher level than the gasoline and is used to introduce the fuel into the vacuum zone of the diffuser. Nozzle performance depends on diameter and vacuum. The nozzle is a small screw with a calibrated orifice. It is positioned at an easily accessible point on the fuel line from the tank.

The diameter of the orifice, known as the nozzle diameter, is expressed in hundredths of a millimeter. By changing it, you can enrich or deplete the mixture and vary engine performance and fuel consumption within a certain range.

The shape and finish of the nozzle are very important because they affect fuel flow and atomization.

Throttle Valve

Located in the duct after the diffuser. It adjusts the amount of fuel admitted according to the power required by the engine. It is controlled by the gas pedal.

Other Models

Carburetor Plug

Motorcycles are often equipped with a needle cup carburetor: the air flow is controlled by a cylindrical cup that is inserted perpendicularly into the air flow. This cup is attached to a conical needle that plunges into the jet, allowing finer control of the air-fuel mixture.

Vacuum Carburetor

The vacuum carburetor is an evolution of the previous model in which the plunger is moved by a diaphragm sensitive to pressure and therefore to air flow, the latter ensured by a butterfly valve. This system prevents the engine from choking when the throttle is suddenly opened, because even when the throttle is wide open, the valve senses that the engine's intake is low and therefore does not require a large amount of gas.

Symptoms of a bad carburetor

The carburetor is not a wearing part, but its channels and jets can become clogged over time. The carburetor can also seize up or jam. Finally, it can become flooded with too much fuel or leak.

The following are signs that your car's carburetor may be faulty or clogged:

• Your car has trouble starting
• Reduced engine performance
• Your car often stalls
• Black smoke coming from the tailpipe

However, these symptoms can be caused by problems other than carburetor failure. You'll need to check the source of the problem.

How does a carburetor work?

The carburetor is an automotive part found on gasoline engines. Its job is to maintain an optimal air-fuel mixture for maximum energy efficiency. They are most commonly found on classic cars, but can also be found on motorcycles and garden equipment.

Carburetors are no longer found on cars produced since the early 1990s, having been replaced by fuel injection systems and throttle bodies. The carburetor is a mechanical part, unlike the injectors, which are electronic.

Did you know that? Carburetors are only found on gasoline engines, not diesel engines.

Carburetors work by using valves and an intake manifold or pipe. It's important to know that a car engine works by burning a mixture of air and fuel. To do this, they must be mixed in the right amounts.

The carburetor's job is to mix the air and fuel in the right way for the best possible combustion.

When ambient air is admitted to the engine, the air filter is there to filter and clean the air collected by the carburetor to be mixed with the fuel sprayed by the jets. The carburetor is also there to manage the flow of fuel sent through the jets. The flow must be constant.

Before reaching the jets, the fuel is placed in a tank whose level must be uniform. A float controls this level. When the level drops, the float pulls and fuel is added to the tank. If the level is too high, a hose is provided to drain the excess fuel.

Once the air and fuel are mixed, the valve opens, the piston is at its lowest point, and everything can be sent to the combustion chamber. There are as many carburetors as there are cylinders, so you'll usually find four.