What is a Fuel Injector?


Fuel is important for cars and other types of vehicles, as it is needed for the engine to create energy to power up the vehicle and allow it to move efficiently. For fuel to be properly distributed from the fuel tank to the engine, the car would need a fuel injector, which is a part that connects the fuel tank to the engine and provides a continuous flow of fuel from those two components. Read below to know more about fuel injectors and their importance for cars.

Components of a Fuel Injector System


Fuel Tank

The fuel tank serves as the engine’s fuel reservoir and will aid in keeping the gasoline’s temperature below the flash point. Additionally, it is resistant to corrosion and leakproof at pressures of at least 30 kPa. A safety valve will be installed in the gasoline tank to release any excess pressure. It will be able to disperse the heat generated by the engine’s fuel.

Fuel Supply Pump

The fuel feed pump is used to provide the injection pump with gasoline from the fuel tank. It uses a push rod and a camshaft to move the spring-loaded plunger. The spring force on the plunger will generate suction in the pump when the push rod is in its lowest position, allowing gasoline to flow from the fuel tank into the injection pump. The plunger is raised when the cam is rotated to the position that allows for the most lift. The gasoline will be pumped via the exit valve once the intake valve has been closed.

Injection Pump

The primary purpose of the fuel injection pump is to deliver the proper quantity of gasoline under strong pressure to the injector. at the proper time to the injector installed in each cylinder head (typically, the range will be 120 to 200 bar).

There are two different types of Injector pumps

  • Jerk-type pump
  • Distributor-type pump


The fuel supplied to the cylinders in compression-ignition engines is unaffected by the parameters of the injection pump and the air intake. The governor’s job is to regulate the amount of fuel based on the load and set a limit when the engine operates at a very high speed with little gear.

Governors are generally of two types

  • Mechanical Governor
  • Pneumatic governor

Fuel Injector

The quick combustion will be dependent on the well-designed fuel injector. A quality fuel injector will atomize the fuel into tiny droplets, increasing their surface area and facilitating the succeeding combustion’s mixing. The following elements make up the fuel injector.

  • Needle valve
  • Compression spring
  • Nozzle
  • Injector body


The Nozzle is the part of the Injector through which the fuel is injected into the cylinder. A schematic cross-section of the single-hole nozzle is shown below.

Any nozzle that wants to be used in a CI engine must meet a few requirements. below is a list of those

  • should be able to atomize the gasoline properly. (Air and fuel are mixed in the combustion chamber)
  • dispersion of fuel throughout the cylinder in opposition to cylinder pressure.
  • preventing gasoline from immediately contacting the piston or combustion chamber walls.
  • even in the event of a non-turbulent kind of combustion chamber, proper fuel mixing.

Types of Fuel Injectors


Single-Point Fuel Injection

A single fuel injector is used by all the cylinders in the engine’s combustion chamber in a single-point injection system. This is the earliest and most basic fuel injection system design. The Single-point injection, also known as throttle body injection (TBI), employs one or two fuel injector nozzles in the throttle body in place of the carburetor. Contrary to the carburetor jet, the gasoline is sprayed simultaneously into each cylinder by an injector, which may be controlled by an electronic control unit (ECU). While it has an advantage over a carburetor, it also has a slight drawback in that it only uses one injector, which interferes with engine performance at high RPMs and results in a rough ride because the necessary fuel supply is not provided. Additionally, a small amount of fuel condenses outside the cylinders’ intake manifold, resulting in fuel waste.

Multi-Point Fuel Injection

Multi-point fuel injection (MPFI) technology, commonly known as “Port Injection,” places an injector in front of each cylinder’s inlet valve (outside the intake port) in the engine’s combustion chamber. Each cylinder receives a more accurate amount of fuel from each injector at the same time, reducing the chance of fuel condensation outside the intake manifold. Even though MPFI uses less gasoline than TBI because all the cylinders receive the same amount of fuel at the same time, the pistons’ rotation is not correctly synchronized. This causes the gasoline to idle for as long as 150 milliseconds in the engine and port. Despite this, MPFIs perform significantly better than TBIs in terms of performance.

Sequential Fuel Injection

The most popular fuel injection technique in use today, sequential fuel injection addresses the one drawback of MPFI. The fuel injectors work about the cylinders they are attached to in a sequential fuel injection system. Only when the cylinder’s intake valve opens does each injector begin to inject fuel. For the remaining actions, it does nothing. An ECU tracks the motion of the cylinders and only activates the injectors when necessary. Of all the fuel injection systems currently offered in the automotive industry, sequential fuel injection is the most effective and efficient.

Direct Injection

In direct fuel injection, the system is focused on placing the injector inside the cylinder to directly inject the fuel, bypassing the intake valve or manifold. Although this kind of fuel injection system is typically found in diesel engines, it is also widely used in gasoline engines under the name GDI (gasoline direct injection). The fuel is sprayed on the intake with the aforementioned methods, therefore there is always a chance of fuel condensation. The major benefit of the DI system is that all of the gasoline is directly injected into the cylinder, resulting in optimum fuel efficiency. Direct fuel injection (GDI) engines have been discovered by automakers to be comparatively more powerful and fairly handy for improved CNG fuel economy. GDI engines have been utilized in diesel engines since the 1920s, whereas they have been employed in petrol engines since approximately World War II.

How a Fuel Injector Works


The fuel injection process

For the engine to run smoothly and efficiently it needs to be provided with the right quantity of fuel /air mixture according to its wide range of demands.

Fuel injection System

Traditionally, the carburetor—a device that is far from ideal—is used to regulate the fuel/air combination. One important drawback is that a single carburetor cannot feed a four-cylinder engine with the same fuel/air mixture for every cylinder since some are farther away from the carburetor than others. Installing dual carburetors is one option, but they are challenging to tune well. gasoline-injected engines, which supply gasoline in precise spurts, are already commonplace in many automobiles. Engines using such equipment are often more effective and powerful than those with carburetors, and they may also be more affordable while also emitting fewer harmful gases.

Diesel fuel injection

Indirect fuel injection is always used in petrol-powered vehicles; instead of injecting gasoline directly into the combustion chambers, it is injected through the input manifold or inlet port. This guarantees that the fuel and air are well combined before entering the chamber. However, a lot of diesel engines use direct injection, where the diesel is injected right into the cylinder that is already filled with compressed air. Others employ indirect injection, in which the diesel fuel is injected into a pre-combustion chamber that is specifically formed and connected to the cylinder head by a small tube. The cylinder is filled with nothing but air. Compression heats the area to such a high temperature that fuel atomized after the compression stroke self-ignites.

Basic injection

Indirect injection is used in every current gasoline injection system. A specialized pump moves the gasoline under pressure from the fuel tank to the engine compartment, where it is delivered to each cylinder separately while still under pressure. Depending on the system, an injector will either shoot fuel into the inlet manifold or the inlet port. This ensures that the gasoline is released as a fine mist and functions similarly to a hose’s spray nozzle. The fuel and air combination enters the combustion chamber as it passes through the inlet manifold or port. In some automobiles, each cylinder is supplied by a separate injector thanks to multi-point fuel injection. This may be costly and tricky. One injector for every two cylinders or single-point injection, where one injector feeds all the cylinders, is more typical.


The fuel injectors, through which the spray is shot, are screwed, nozzle-first, into the cylinder head or the intake manifold and are slanted to direct the fuel spray in the direction of the inlet valve. Depending on the injection mechanism, there are two different types of injectors. With the first system, fuel is continuously injected into the inlet port while the engine is running. The injector does not regulate the fuel flow; it only serves as a spray nozzle to disperse the gasoline into a thin mist. A mechanical or electrical control device, which is similar to turning a faucet on and off, controls how much gasoline is sprayed out. The second common approach is timed injection, sometimes known as a pulsed injection, in which gasoline is given in bursts to match the cylinder’s induction stroke. The timed injection can also be managed physically or electrically, much like a continuous injection. The early systems were run by mechanical means. They are frequently referred to as petrol injection (PI for short), and a mechanical regulator assembly regulates the fuel flow. These systems have the flaws of being mechanically complicated and not responding well when the throttle is backed off. Mechanical systems have now been largely superseded by electronic fuel injection (known as EFi for short). This is due to electronic control systems’ rising dependability and falling prices.


In summary, fuel injectors are an important part of an automobile’s engine that delivers a constant flow of gasoline from the fuel tank to the engine. The gasoline tank, fuel supply pump, injection pump, governors, and fuel injector are all components of the fuel injector system. Fuel is atomized by the fuel injector into small droplets, increasing their surface area and assisting in the mixing of the subsequent combustion. Fuel injectors come in a variety of designs, including single-point, multi-point, sequential, and direct injection fuel injectors. Although each has benefits and drawbacks, sequential fuel injection is thought to be the most efficient and effective. Overall, a well-designed fuel injector system is necessary for a car to operate efficiently, use less gasoline, and emit fewer pollutants.