What is Carburetor?- Definition, Types & How it works

The fuel system in a vehicle features many parts that help store and supply the engine with the fuel it needs to run. Gasoline gets mixed with air, and this mixture burns inside cylinders to generate power that gets the car moving.

A carburetor is a part responsible for mixing these components in the right amounts so the combustion process can occur. While carburetors aren’t used in late-model vehicles, they were used for many years until the introduction of electronically controlled fuel-injection systems.

Keep reading to learn more about how carburetors work and how they were used to deliver fuel to engines of many vehicles through the years.

What is a carburetor?

A carburetor is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances.

Carburetors add fuel to air to make a mixture that’s just right for burning in the cylinders. Modern car cylinders are fed more efficiently by fuel-injection systems, which use less fuel and make less pollution.

But you’ll still find carburetors on older car and motorcycle engines and in the compact engines in lawnmowers and chainsaws.

Gasoline engines are designed to take in exactly the right amount of air so the fuel burns properly, whether the engine is starting from cold or running hot at top speed.

Getting the fuel-air mixture just right is the job of a clever mechanical gadget called a carburetor: a tube that allows air and fuel into the engine through valves, mixing them together in different amounts to suit a wide range of different driving conditions.

You might think “carburetor” is quite a weird word, but it comes from the verb “carburet.” That’s a chemical term meaning to enrich a gas by combining it with carbon or hydrocarbons. So, technically, a carburetor is a device that saturates air (the gas) with fuel (the hydrocarbon).

What Does a Carburetor Do in an Engine?

A carburetor’s task is to mix the right amount of gasoline and air together. Despite what you might have assumed, gasoline when in its liquid form, isn’t actually flammable. In fact, it’s the fumes that ignite.

A carburetor takes the liquid gasoline from the gas tank and mixes it with air, which then travels to the combustion chamber, where the mixture is ignited by the spark plug.

Of course, the air-fuel mixture has to be just right. A well-performing engine needs the Goldilocks-like calibration of the carburetor. If there is not enough fuel mixed with the air, the engine “runs lean” and either will not ignite, or potentially damage the engine.

If there is too much fuel mixed with the air, the engine “runs rich” and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel.

Functions of carburetors:

The main functions of carburetors are

• The main function of carburetors to mix air and gasoline and provides a high combustion mixture.
• It controls the engine speed.
• It also regulates the air-fuel ratio.
• Increase or decrease the amount of mixture according to the engine speed and load changes.
• To keep a certain head of fuel in the float chamber all the time.
• Vaporize the fuel and mix to air to a homogeneous air-fuel mixture.
• To supply the correct amount of air-fuel mixture at the correct strength under all conditions of load and speed of the engine.

Who invented the carburetor?

The first carburetor was invented by Samuel Morey in 1826. The first person to patent a carburetor for use in a petroleum engine was Siegfried Marcus with his 6 July 1872 patent for a device that mixes fuel with air.

A very simplified diagram of Karl Benz’s original carburetor from his 1888 patent. Fuel from the tank enters what he called the generator underneath, where it evaporates.

The fuel vapor passes up through the gray pipe and meets air coming down the same pipe, which enters from the atmosphere through perforations at the top. The air and fuel mix in the chamber then pass through a valve into the cylinder, where they burn to make power.

How Does a Carburetor Work?

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 is what 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 more or less air to enter the engine.

A more open throttle will allow more 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.

Parts of Carburetor

The following are the Parts of the Carburetor:

• Throttle Valve
• Strainer
• Venturi
• Metering system
• Idling system
• Float Chamber
• Mixing Chamber
• Idle and Transfer port
• Choke Valve

• Throttle Valve: It is a valve designed to regulate the supply of a fluid as steam or gas and air to an engine and operated by a handwheel, a lever, or automatically by a governor especially.
• Strainer: It is a device that is used to filter the fuel before entering the float chamber. It consists of a fine wire mesh that filters the fuel and removes dust and other suspended particles from it. These particles if not removed can cause blockage of the nozzle.
• Venturi: The air passes through a narrowed neck inside the carburetor called a venturi, which speeds up its flow at that point. As air flows faster its pressure drops, so there is a slight vacuum inside the venturi. The fuel jet opens into the venturi, and the partial vacuum sucks fuel through the jet into the air stream.
• Metering system: The fuel discharge nozzle is located in the carburetor barrel so that its open end is in the throat or narrowest part of the venturi. It is this pressure difference, or metering force, that causes fuel to flow from the discharge nozzle.
• Idling system: It provides the air-fuel mixture at speeds below approximately 800 rpm or 20 mph When the engine is idling, the throttle is almost closed Air flow through the air horn is restricted to produce enough vacuum in the venturi.
• Float Chamber: A float chamber is a device for automatically regulating the supply of a liquid to a system. It is most typically found in the carburetor of an internal combustion engine, where it automatically meters the fuel supply to the engine.
• Mixing Chamber: In the mixing chamber, the mixture of air + fuel occurred. And then supplied to the engine cylinder.
• Idle and Transfer port: In addition to the main nozzle in the venturi portion of the carburetor, two other nozzles, or ports, deliver fuel to the engine cylinder.
• Choke Valve: A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine.

Types of Carburetor

There are three types of carburetors:

• Up-draft carburetors
• Horizontal type carburetors
• Down-draft type carburetors

Up-draft type carburetors

An updraft carburetor is a type of carburetor a component of engines that mix air and fuel together in which the air enters at the bottom and exits at the top to go to the engine.

An updraft carburetor was the first type of carburetor in common use. In an updraft carburetor, the air flows upward into the venturi according to Edward Abdo in Power Equipment Engine Technology. Other types are downdraft and side-draft carburetors. An updraft carburetor may need a drip collector.

Down-draft Carburetors

This carburetor operates with lower air velocities and larger passages. This is because gravity assists the air-fuel mixture flow to the cylinder.

The downdraft carburetor can provide large volumes of fuel when needed for high-speed and high-power output.

In this type of carburetor air comes from the top of the mixing chamber, and the fuel comes from the bottom of the mixing chamber, here also the same principle works, due to low pressure created by the two venturis fuel comes out through the pipe and then the mixing of fuel and air occurred here.

Horizontal Type Carburetors

This type of carburetor is used when we have the constraint of space for assembly. In horizontal or side draught carburetor, as the name suggests, the jet tube is placed in a horizontal direction. One more advantage of this type of carburetor is that it reduces the resistance of the flow due to the absence of the right-angle mechanism in the intake area.

The working principle of this type of carburetor is very simple. Here the carburetor stays in the horizontal position where the air is coming in through one end of the carburetor shown in the below figure. And mixed with fuel to make the air-fuel mixture and then the air-fuel mixture is going to the engine cylinder for combustion.

Signs Your Carburetor Is Failing

Here comes the first sign your carburetor needs cleaning, which is:

Engine Performance Reduction

As mentioned above, combustion starts and keeps your engine running. The air and gas mixture must be just so in order for you to get maximum performance out of your car, truck or SUV.

Signs you have trouble brewing within your carburetor include sluggish acceleration and reduced engine power. You may also notice your vehicle isn’t getting the gas mileage it used to.

Black Exhaust Smoke

You shouldn’t see black smoke coming out of your exhaust pipe even if you drive a diesel. Black smoke, whether steady or just when you accelerate indicates a rich fuel mixture. This means the carburetor is using too much fuel in the fuel/air mixture.

As you can imagine, this rich mixture burns excess fuel which is why you get fewer miles to the gallon. It also emits excessive emissions.

Engine Backfires or Overheats

The opposite of a rich fuel mixture is a lean one and this can cause your engine to backfire or overheat. Performance suffers when the vehicle’s engine is starved of fuel and it must work harder to maintain speed.

An overworking engine will overheat and an engine filled with too much air will backfire. It should be noted, however, than a rich mixture can also cause backfires.

Starting Difficulty

If you have trouble starting your car, truck or SUV, your fuel/air mixture could be off. Of course, difficulty starting an automobile can also be a sign of a dying battery or starter.

In most cases, the vehicle will be impossible to start when cold but might start easier when warm because the battery has charged during operation. If you can’t start your car in either situation, it could be your carburetor.

Fuel Flooding Into The Carburetor

Here comes another sign, which is the fuel flooding into the carburetor.

When the fuel bowl is dusty, the needle valve is unable to close. As a result, fuel can overflow into the carburetor. Due to this, the excess fuel escapes through the bowl vents after filling the carburetor & you know it also soaks the spark plugs.

This demonstrates the dangerous extent of an uncleaned carburetor that results in a flooded engine and other issues.

How To Clean A Carburetor?

Check your Owner’s Manual before cleaning the carburetor. Always follow the manufacturer’s complete instructions for cleaning and maintenance. Make sure the carburetor is cool to the touch before cleaning.

1. Dilute cleaner: In a large container mix dilute cleaner, However, it’s important to use a non-corrosive cleaner that doesn’t harm or degrade any plastic or rubber pieces on the carburetor. You should avoid using vinegar because the acetic acid makes metal susceptible to rust. Additionally, bleach should never be used, because sodium hypochlorite (bleach) will corrode metals such as steel and aluminum, and degrade rubberized seals.
2. Clear air filter: Before cleaning your carburetor, check the air filter to make sure that the air coming into the carburetor is clean and free of blockage, which can result in black smoke emissions from the exhaust. Shut off the fuel supply and disconnect the spark plug wire, if one exists. Remove the housing and the wing nut attaching the filter, and remove the outer element. Use a can of compressed air to remove debris.
3. Remove the carburetor: Remove any covering plate or shield, as well as linkage and hoses using pliers and a screwdriver, where necessary. Also, remove any cover or clamps holding the carburetor in place, and remove the hose clamp that connects it to the fuel line. And remove the carburetor, and use compressed air to blow off any excess dirt on the outside casing. (Note: if unfamiliar with this procedure, consult with a professional before cleaning.)
4. Remove carburetor float: Remove the bolt holding the carburetor float (bowl-shaped container) in place, being careful not to spill any remaining gas inside the float (dispose of this securely). This is a common point of varnish buildup on carburetors. Also, remove the pin that the float pivots on, and place it aside in a safe spot. Now pull the float straight out of its casing.
5. Remove other removable components: Note the location and placement of any other carburetor components you’re removing to allow cleaning access.
6. Soak and scrub components: Submerge the carburetor float and other components in a large container with your dilute cleaner, and soak thoroughly for 10 minutes. Use a brass brush to scrub all metal components, and a stiff nylon brush to scrub plastic pieces. Make sure the tiny vents get cleaned. Clean the small parts in the cleaning solution as well.
7. Rinse and dry: Rinse all carburetor components in a bucket of clean water, and allow to air dry completely. For small holes and vents, use a can of compressed air to remove any excess moisture.
8. Reassemble and replace: Carefully reassemble the carburetors, and mount them to the engine. Re-link all hoses, clamps, and wires.

Advantages of the carburetor:

• Carburetor parts are not as expensive as that fuel injectors.
• With the use of a carburetor, you get more air and fuel mixture.
• In terms of road tests, carburetors have more power and precision.
• Carburetors are not restricted by the amount of gas pumped from the fuel tank which means that cylinders may pull more fuel through the carburetor which would lead to a denser mixture in the chamber and greater power as well.

Disadvantages of the carburetor:

• At very low speeds, the mixture supplied by a carburetor is so weak that, it will not ignite properly and for its enrichment, at such conditions, some arrangement in the carburetor is required.
• The working of a carburetor is affected by changes in atmospheric pressure.
• More fuels are consumed since carburetors are heavier than fuel injectors.
• More air emissions than fuel injectors.
• The maintenance costs of a carburetor are higher than the fuel injection system.

Applications of Carburetor:

• Used for Spark-Ignition Engine.
• It is used to control the speed of the vehicles.
• It converts the main fuel petrol into fine droplets and mixes with air to burn in smoothly and properly without any problem.

FAQs.