How does a Carburetor work? | How to Clean a Carburetor?

The engine is a most important part of a vehicle. The amount of air and fuel required by an engine varies according to the vehicle model, the operating speed, and various other factors. The latest diesel engines have an electronic control system known as fuel injection. The petrol engine has a carburetor (spelled “carburettor or carburator”). A carburetor is a device that supplies a mixture of air and fuel to a spark-ignition engine. This article mainly explains the working, types, and many other aspects of the carburetor.

What is Carburetor?

carburetor is a mechanical unit that mixes the air and fuel up to a specific fuel-air ratio and sends it to the IC engine for combustion. In simple words, a carburetor is a tube that sucks fuel and air through valves, mix them and sends this mixture to the engine to drive the vehicle.

The main function of the engine is to generate power by burning the air-fuel mixture and runs the vehicle. A carburetor is known as the “heart” of a vehicle engine. When the “heart” doesn’t work properly, you can’t expect the engine to work properly or can’t get adequate power. If the engine doesn’t work properly, your vehicle couldn’t run smoothly.

Carburetor
Diagram of Carburetor

The carburetor firstly sucks air from the environment, mixes it with an appropriate amount of fuel, and sends this mixture into the compression cylinder of the IC engine.

The carburetor has an accelerator pump, venturi tube, main jet, idle (or slow speed) jet, a choke, and a liquid fuel storage chamber.

A valve uses to control the amount of fuel in the storage cylinder. A float uses to operate this valve. The choke uses to reduce air intake and permits a fuel-rich charge to enter the cylinder when starting a cold engine.

When the engine heats up, the choke opens automatically or manually or by engine speed and temperature controllers.

The latest automotive cylinders have fuel injection systems instead of carburetors. These systems supply fuel more efficiently, use a low amount of fuel and reduce pollution. However, the carburetors are still used in old motorcycle engines, car engines, compact chainsaws, and lawnmowers.

How does an engine burn fuel?

An engine is a mechanical device that generates power by a chemical reaction of fuel and air. This chemical reaction is known as combustion. Here we will discuss the working of a petrol engine.

Petrol Engine working

First of all, the engine carburetor takes air from the atmosphere. As the air enters the carburetor, a fuel pump injects fuel into the float chamber (or fuel storage chamber).

A mixing chamber takes fuel from the float chamber and makes a fuel-air mixture. The carburetor sends this fuel-air mixture into the combustion or compression chamber of the engine.

The combustion chamber has a reciprocating piston. As the air-fuel mixture enters the chamber, the piston compresses it up to desired pressure and temperature.

When the mixture is compressed according to the requirements, a spark plug generates a spark and ignites the air-fuel mixture.

Due to the air-fuel mixture combustion, power generates which uses to move the piston downward. This downward motion of the piston further moves the crankshaft and crankcase. The crankshaft transfers its motion to the flywheel, which moves the vehicle wheels.

Read Also: Different types of Engines

Who invented the carburetor?

  1. In 1826, Samuel Morey was invented the first carburetor. Siegfried Marcus was the 1st engineer who invented a carburetor on 6 July 1872 for the gasoline engine, which mixes air and fuel.
  2. The carburetor is one of Karl Benz’s first patent (1888) who invented the IC engines and their parts.
  3. Gottlieb Daimler and Wilhelm Maybach designed a float carburetor based on the atomizer nozzles in1885. The Daimler-Maybach carburetor was copied many times and led to patent proceedings.
  4. The British courts dismissed Daimler’s priority action in favor of Edward Butler’s aerosol carburetor, which was employed in his gasoline cycle in 1884.
  5. In 1893, the Hungarian engineers Donát Bánkiand János Csonka designed carburetors for stationary engines.
  6. In the 1990s, few car models started to use carburetors in Australia. These models were Suzuki Swift (1999), Daihatsu Charade (1997), Mitsubishi Magna Sedan (1996), Mazda 323, Ford Laser (1994), and Honda Civic (1993).

Working Principle of Carburetor

A carburetor works on Bernoulli’s principle. According to Bernoulli’s principle, as the air flows faster, its dynamic pressure increases, and the static pressure reduces. The throttle (accelerator) linkage doesn’t directly regulate the liquid fuel flow.

However, the throttle linkage activates the carburetor mechanism to measure the delivered airflow to the engine. The speed of this air flow and its static pressure help to determine the quantity of fuel sucked in by the airflow.

When the carburetor installs in an airplane equipped with a reciprocating engine, special construction and functionality are required to avoid fuel shortages during reversed flight. With time, engines started to use an old type of fuel injection called pressure carburetors.

A carburetor which works on Bernoulli’s Principle has a drawback that in this carburetor, the venturi pressure drop is proportional to the square of the inlet air velocity. The liquid fuel flow is often proportional to the pressure difference because the fuel jet is much smaller, and the fuel flow is controlled by the viscosity of the fuel.

Working of Carburetor

A carburetor is a most vital part of an internal combustion engine. The main purpose of the carburetor is to supply air-fuel mixture to the engine properly.

Working of Carburetor
Working of Carburetor

A carburetor works in the following way:

  • First of all, a strainer gets fuel (petrol or diesel) from the storage tank and transfers it into the float chamber. This strainer acts as a filter. It removes debris and other solid contaminations from the fuel, which may block the fuel passages.
  • A float uses to maintain a specific level of fuel inside the float chamber. As the fuel level inside the float chamber becomes lower than the desired level, the float moves downward.
  • The downward motion of the float opens the fuel delivery valve and permits the fuel to enter the float chamber. As the fuel limit becomes equal to the desired limit, the float rises, the fuel delivery valve closes, and fuel delivery into the float chamber stops.
  • The venturi tube and float chamber are connected through a fuel discharge nozzle.
  • One end of the fuel discharge nozzle connects with the venturi tube, while the other end connects with the float chamber base. It is installed slightly above the float chamber bottom (as shown in the above diagram). This design prevents overflow when the engine is shut off.
  • During the suction process, the air firstly enters the cylinder via a venturi tube. This tube has a gradually decreasing cross-section and the smallest area at the throat.
  • The fuel discharge nozzle is connected to the venturi tube throat. As the air enters the throat, its velocity becomes very high. Because of this high speed, the air pressure inside the throat becomes less than the fuel pressure in the float chamber.
  • In this way, a pressure difference generates between the venturi tube and float chamber. This pressure difference is called carburetor depression. This works as a driving force for fuel.
  • As the pressure difference generates, the fuel starts to go from the float chamber into the venturi tube via a fuel delivery valve.
  • The air-fuel ratio varies according to the size of the metering system and the discharge jet. As the air and fuel mixing process is completed, the throttle valve opens, and the air-fuel mixture is delivered into the cylinder.
  • In the case of the SI engine, the cylinder has a reciprocating piston. This piston compresses the air-fuel mixture and generates power.
  • When the engine needs a rich mixture, an idling system uses to supply additional fuel in the venturi tube.

For better understanding the carburetor working, watch the following video:

Read Also: Different types and Working of Petrol Engine

Types of Carburetors

The carburetor has the following major types:

  1. Down-draft Carburetor
  2. Up-draft type carburetor
  3. Horizontal Type Carburetor

1) Down-draft Carburetor

In the down-draft carburetor, fuel is supplied from the mixing chamber base, and the air is supplied from the top of the carburetor.

Down-draft Carburetor

The down-draft carburetors work on the same principle as the up-draft carburetors. In this type, the fuel also comes from the fuel pipe due to pressure differences. As the desired quantity of air and fuel comes into the mixing chamber, the air and fuel mixing process occur.

A choke valve uses to control the produced air-fuel mixture, and a throttling valve uses to regulate the air-fuel mixture supply to the engine.

Read Also: Different types of Diesel Engines

2) Up-draft type Carburetor

In the up-draft type carburetors, the air is supplied from the base of the carburetor, and fuel is provided by the float chamber.  

Up-draft type carburetor

As the pressure difference produces between the venturi tube and the float chamber, the fuel leaves the float chamber with the help of the Venturi tube and mixes with the intake air and metering system makes a flow-air mixture.

The throttle valve opens as the driver presses the accelerator, and the fuel-air mixture enters the engine chamber. As the mixture enters the combustion chamber, the fuel combustion process starts, and power is produced to run the vehicle.

3) Horizontal Type Carburetor

As you turn the down-draft carburetor horizontally, it converts into a horizontal carburetor.

Horizontal type carburetor

In these types of carburetors, air enters from one side of the carburetors. After fuel and air entry, the mixing chamber mixes air with fuel to form an air-fuel mixture. This produced mixture is sent to the combustion chamber for producing power.  

Read Also: Different types of Reciprocating Engines

How to Clean a Carburetor?

  1. Detergent dilution: Use a detergent to clean the carburetor. Mix the diluted detergent in a large tank. But you must use a non-corrosive detergent that can’t damage the rubber or plastic parts of the carburetor.
  2. Use of Bleach: Don’t use a vinegar, as acetic acid can make metals more prone to oxidation. Also, do not use bleach, as sodium hypochlorite (bleach) attacks metals such as aluminum and steel and damage the rubber seal.
  1. Clean the air filters: Before cleaning the carburetor, clean the air filters and ensure that the air entering the carburetor contains no dust and other contaminations.
  2. To clean the filters, detach the spark plug wires (if equipped) and turn off the fuel supply. Remove the casing and wing nuts connecting the filter, and remove the external components. Use an air blower to blow air into the filter and remove the dust.
  1. Detach the carburetor: Use a screwdriver and pliers to detach the covers and guards, as well as the hoses and linkage. You must also remove all other clamps or cover that fix the carburetor on its place. Also, disconnect the hose clamps connecting the fuel line to the carburetor. After all these processes, detach the carburetor and use a blower to blow compressed air to remove dust from its housing.
  2. Removal of the carburetor float: Detach the fastening screws of the carburetor float (bowl-shaped container) and make sure that no residual gas is sprayed in the float (dispose of properly). Remove the pin that rotates the float and keep it in a safe place. Then detach the float by pulling it directly from its housing.
  3. Remove all other detachable parts: Remove all other detachable parts of the carburetor for its cleaning. Remember the position and location of all the removable parts so that you can easily reinstall them at their exact locations.
  4. Soak and Scrub Parts: Soak the carburetor float and other parts in a large tank of diluted detergent and let them immerse for up to 8 minutes. Wash all plastic parts using a stiff nylon brush and metal parts using a brass brush. Be sure to clean the small ventilation holes. You must also use the diluted detergent solution to clean the other small parts.
  5. Rinse and Dry: Rinse all the parts of the carburetors by using a clean water bowl and dry them completely. To remove extra water, use a blower to blow dry compressed air from the small holes and vents.
  6. Reassembly and replacement: Carefully reassemble the carburetor and secure it to the engine. Reconnect all cables, clamps, gaskets, and hoses on their locations.

Read Also: Working of Power Steering System

Parts of Carburetor

The car carburetor has the following major components:

  1. Throttle valve
  2. Venturi tubes
  3. Strainer
  4. Metering system
  5. Mixing chamber
  6. Idling system
  7. Float chamber
  8. Choke valve

Parts of Carburetor

1) Throttle Valve

This valve is a major part of the carburetor. The throttle valve regulates the amount of the air-fuel mixture delivered to the engine cylinder. As you press the car accelerator, the throttle valve opens.  

2) Venturi Tube

Venturi tubes are hollow tubes whose cross-section gradually decreases and smallest area at the throat. This tube assists in reducing the float chamber air pressure. The air enters at low speed, but when it leaves the venturi tube, its pressure becomes very low while velocity highly increases.

3) Strainer

A strainer filters the fuel before sending the fuel into the float chamber.  

The strainer has a fine wire mesh that cleans the fuel by eliminating dirt and other suspended matter. If it doesn’t remove these dirt particles, the dirt particles may clog the nozzle.

4) Metering System

This part of the carburetor regulates the fuel flow into the nozzles. The metering system has a responsibility to make a fuel-air mixture according to desired air-fuel ratio.  

This system has the following two major parts:

  1. Fuel discharge nozzle
  2. Metering orifice and

As the air passes by the venturi tube, it creates a low-pressure field at the throat. This pressure difference causes the fuel to flow in the air stream.

The amount of fuel is controlled by the metering orifice and the discharge hole located at the outlet of the fuel drainage nozzle.

5) Mixing Chamber

This chamber uses to mix the fuel and air. After the mixing process, the fuel-air mixture is delivered to the engine combustion chamber.

6) Idling System

This system has a direct passage from the float chamber to the venturi. It has a responsibility to deliver a rich mix at slow speed and during idling. The idling system activates when the idle speed or the throttle opening is less than 15%.

7) Float Chamber

This chamber works as a fuel storage tank to supply fuel into the engine. The float chamber has a float valve to maintain the fuel level inside the chamber.

As the fuel level in the float chamber becomes lower than the fixed level, the float moves down and opens the fuel supply valve. As the fuel supply valve opens, the fuel starts to enter the float chamber.

When the fuel level becomes equal to the required level, the float moves up, closes the valve, and stops the fuel flow.

8) Choke Valve

The choke valve uses to regulate the air-fuel mixture. This valve only controls the amount of air in the mixing chamber.

This valve is usually in a half-open and half-closed position. When the engine needs a rich mixture, you press the choke valve. This valve stops the airflow into the chamber so that the engine can receive the rich fuel-air mixture.  

In winter, when the engine does not start, this valve is used to deliver a rich fuel-air mixture to the engine cylinder. In this way, the air-fuel mixture burns quickly, and the engine starts.

Read Also: Different types of Valves

Advantages and Disadvantages of Carburetors

Advantages of Carburetor

  1. The carburetors have low costs than the fuel injection systems.
  2. It needs low maintenance cost.
  3. The carburetor has higher precision and power than the fuel injectors in terms of road text.
  4. These systems require low maintenance and repair.
  5. The carbureted motorcycle has low cost than the fuel-injected motorcycle.
  6. A well-maintained carburetor has a high service life.

Disadvantages of Carburetor

  1. It consumes more fuel than the fuel injector.
  2. The motorcycles having carburetors have a high emission rate.
  3. They are not as environmentally friendly as fuel injectors.
  4. These are old-fashioned devices.
  5. In winter, a carbureted vehicle is very hard to start.
  6. They waste more fuel than fuel injectors.

Applications of Carburetor

  • They are used for SI engines.
  • The carburetors use to regulate the car speed.
  • They transform the petrol into small droplets and mix them with the air to make an air-petrol mixture.

Carburetor Vs Fuel Injection

The main difference between the carburetor and fuel injection system is given below:

CarburetorFuel Injection
The carburetor first mixes the air and fuel and then sends the air-fuel mixture into the engine cylinder.In a fuel injection system, the air and fuel mixing process takes place after their entry into the engine.
It is designed by using conventional technology.It is designed using the latest technology.
In winter, the carbureted vehicle is very hard to start.Fuel injection-based vehicles have an easy start-up, even in a cold climate.
It works for a long time if you properly maintain it.A properly maintained fuel injection system also has a long service life.
The carbureted vehicles generate more emissions than fuel-injected vehicles.The fuel-injected vehicle generates very low emissions.
The carburetor has a low cost.The fuel injection systems are expansive.
It doesn’t have superior features as a fuel injector.It has excellent features such as low fuel economy and emission rate.
It can’t adjust the air-fuel ratio according to the engine condition.It has the capability to adjust the air-fuel ratio according to the engine requirements.
The carburetor wastes more fuel than the fuel injection.The fuel injector wastes a very low amount of fuel.
It has simple cleaning and maintenance.It has complicated cleaning and maintenance.
This system requires very low maintenance.It requires regular and high maintenance.
The carburetors are most commonly used in petrol engine vehicles.The fuel injection systems are most commonly used in diesel engine vehicles.

FAQ Section

What does a carburetor do?

A carburetor mixes the air and fuel according to the desired air-fuel ratio and then transfers the air-fuel mixture to the engine cylinder.

What is the functions Of Carburetor?

  1. This part of the engine mixes air and petrol according to desired air-petrol ratio.
  2. It upholds a very small amount of fuel in the float chamber at a specific level.
  3. The carburetors atomize and vaporize the fuel.
  4. They generate a homogeneous mixture.
  5. The carburetor is responsible to deliver a proper amount of air-fuel to the engine under all conditions such as load, speed, temperature and pressure.  

What is the purpose of Carburetor in an engine?

The main function of a carburetor is to make an air-fuel mixture and transfer it to the engine for the combustion process.

In which type of engine, we use a carburetor?

The carburetors are only used in petrol engines.

Carburetor works on which principle?

A carburetor works according to Bernoulli’s principle.

Who invented the first Carburetor?

In 1826, Samuel Morey was designed the first carburetor. Siegfried Marcus was the 1st engineer who invented a carburetor on 6 July 1872 for the gasoline engine, which mixes air and fuel.

Read Also
  1. Different types of Engines
  2. Different types of Internal Combustion Engines
  3. Types of Heat Engines
  4. Types of Petrol Engines
  5. Working of Planetary Gearbox

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