What is Fuel Injector, and How Does it Works?

By CarsFellow 10 Min Read

As humans, we are surrounded by machines nowadays; it makes our lives easy and increases the fuel demand as well. Especially in the automobile industry, the increasing trend of vehicles makes the fuel demand and prices high.

So the necessity forces researchers to innovate a system that makes drive reliable and affordable. A fuel injector is one of the modern inventions which boom the field of the automobile industry.

What is Fuel Injector?

A fuel injector is defined as electronically controlled mechanical equipment. It is usually placed at a particular angle to inject just the right amount of fuel into the engine’s combustion chamber.

Fuel injectors are designed to be open and close many times per second. The position of the fuel injectors might be different for different engine designs. They mounted on the engine head with a tip inside the combustion chamber of the engine. They control the fuel to air ratio in a way to be perfectly combustible.

Why We Need Them?

Fuel injectors are modern technology that is now a day’s basic necessity of all automobile vehicles.

In the internal combustion engine, the quality of the fuel-air mixture indicates the better efficiency of the engine. To get the engine’s high efficiency, we need fuel injectors that provide better air-fuel mixture quality than carburetors.

Carburetors provide improper air-fuel mixing, which leaves various unburned particles inside the combustion chamber. Engine issues like detonation or knocking arise due to the improper mixing of air-fuel mixing. Almost all vehicles now a day’s use fuel injection technology to avoid damage to engines.

To make vehicles economical, adopting fuel injection technology is essential. The improper mixing of air-fuel causes the wastage of fuel to inform unburned carbon particles inside the combustion chamber. That un-burned particles directly relate to the mileage of the vehicle.

Types of Fuel Injectors

The invention of fuel injection technology gave rise to various arrangements for the combustion engine.

All are used according to the application. There are multi-point fuel injections, sequential fuel injection, direct injection, and throttle body fuel injection.

The types of fuel injectors are categories as.

1. Based on Fuel Metering

Question arsis what is metering?

Metering is used to control the speed, quantity, and pressure of the fuel. Based on metering, fuel injectors are of 2 types.

2. Mechanically Controlled Fuel Injectors

In this type, as the name suggests, the fuel speed, quantity, timing, and pressure are controlled with the help of spring and plunger mechanically. It takes the input from the cam and fuel distributor.

3. Electronically Controlled Fuel Injectors

This type of fuel injector electronically controlled all its working. It controls the quantity, speed, pressure, and timing with the help of an electronic solenoid. It takes the input from the electronic control unit, which is an advanced one, or from the fuel distributor.

  • Based on Fuel

Based on fuel, the fuel injectors are of 2 types as.

  • Diesel Fuel Injectors

Everyone knew that diesel is a heavier liquid than gasoline. So diesel fuel injectors are engineered slightly differently than gasoline fuel injectors.

These fuel injectors inject the diesel directly into the diesel engine’s combustion chamber for further combustion by compression.

The diesel fuel injectors are made to form a diesel packet while sparing the fuel inside the combustion chamber. These fuel injectors required higher injection pumping than the other injectors as diesel is a heavier liquid.

  • Gasoline Fuel Injectors

These fuel injectors inject or spray gasoline through the intake manifold into the combustion chamber for further combustion by a spark.

The capillary and nozzle of these injectors are engineered smaller than the diesel fuel injectors. Gasoline injectors required less injection pumping than diesel injectors, as gasoline is lighter than diesel.

Construction of Fuel Injectors

The constructional design of fuel injectors easily understand by a pretty excellent example is the garden shower nozzle. It is used to spray water over grounded grass; a fuel injector uses the same phenomenon. The only difference is that fuel is injected instead of water inside the engine.

Let’s understand the construction design considering mechanically controlled fuel injectors and electronically controlled fuel injectors.

1. Mechanically Controlled Fuel Injector:

The injector body is the shell inside which all the parts of the injectors are arranged. It holds a precisely designed capillary through which pressurized fuel from the fuel pump can flow for further spray.

  • Plunger – At the nozzle or narrow end of the fuel injector, a plunger is placed. Plunger plays a rule to open or close the nozzle under the action of fuel pressure governed by the fuel distributor.
  • Springs There are two types of springs used inside the mechanically controlled fuel injectors.
  • Plunger springPlunger spring controlled the to and fro motion of the plunger, which operates when the fuel pressure inside the fuel injector increases. Resulting in the nozzle opening and returns to its initial position when the pressure decreases, in turn, closes the nozzle.
  • Mainspring To controls the inlet of the fuel injector, the mainspring is used. It operates under the fuel pressure provided by the fuel pump.

2. Electronically Controlled Fuel Injector:

Electronically controlled fuel injectors designed of following parts –

  • Injector bodyJust likes the mechanically controlled fuel injector, the body of this type of injector is designed in which all the other components are arranged.
  • Plunger Electronically controlled fuel injector has a plunger that is used for the opening and closing of the nozzle. Also, in an electronically controlled fuel injector, the opening of the nozzle is controlled electronically with the help of electromagnets.
  • Spring A plunger spring is used to hold the plunger in its position to close the fuel injector’s nozzle when required.
  • Electromagnets – In this injector, they are just around the plunger to control the opening of the nozzle. It provides the electronic signal from the engine’s electronic control unit, connecting the fuel injector with the engine’s electronic control unit.
  • Electronic plugA plug is present at the top end of an electronically controlled fuel injector. The electronic signal from the engine’s electronic control unit is transferred to the electromagnets, which opens the nozzle to spray the fuel.

How Does A Fuel Injector Work

To understand the behavior of the various parts of the fuel injector, let’s consider the mechanical and electronic fuel injectors to fulfill that purpose.

1. Mechanically Controlled Fuel Injector

When highly pressurized fuel reaches its high pressure in a fuel injector, this fuel pushes the inlet or mainspring to enter the fuel injector. When this fuel enters the fuel injector, it pushes the plunger spring, pushing the plunger outward, resulting in the nozzle opening. It allows the fuel to spray.

When the cycle is completed according to the input given by the fuel distributor, as a result, the pressure decreases; the plunger spring retains its initial position, and the spray of the fuel stops for that cycle.

2. Electronically Controlled Fuel Injector

The ECU delivers an electronic signal to the fuel injector with the help of the electronic connection. The electromagnets inside the fuel injector got activated due to the electronic signals from the ECU. Which pushes the plunger outward, results in an opening of the nozzle, and finally, the spray of the fuel takes place.

After completion of the cycle, the electronic signal from the ECU stopped. The plunger returns to its initial position, resulting in closing the nozzle and stopping the spray.


A fuel injector is an excellent innovation of engineering. It solves the problem of delivering the exact amount of fuel for combustion. Compared to the carbureted engine, the fuel injector helps the automobile industry achieve better transient throttle response and better efficiency.

In fuel injectors, the valves allow more fuel to flow quickly, which could not do by carbureted engines.

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