What is a Fuel Injector?

Bosh created the fuel injector for a diesel engine in 1920 as a response to rising fuel demands and prices. Since the introduction of fuel injection in vehicles, the speed and acceleration of many have hyped making motors more fuel efficient, effective, and higher horse powered. This is the technology we are enjoying every day in our vehicles.

What is a Fuel Injector?

A fuel injector is a device for actively injecting fuel into an internal combustion engine by directly forcing the liquid fuel into the combustion chamber at an appropriate point in the piston cycle. Fuel injectors can also act as an alternative to a carburetor, in which an air-fuel mixture is drawn in by the downward stroke of the piston.

Typically, fuel injectors are mounted on the engine head with a tip inside the combustion chamber of the engine, but angles can vary from engine to engine.

Why do we Fuel Injectors?

Fuel injectors are necessary components of vehicles because:

• The working principle of internal combustion engines directly indicates that the better the quality of fuel-air mixture will result in better combustion which, , provides higher engine efficiency.
• The improper air-fuel mixing provided by carburetors leaves various un-burned particles inside the combustion chamber of an internal combustion engine. This leads to improper propagation of combustion flame due to a malfunctioning known as “knocking.”
• The waste of fuel in the form of carbon or un-burned particles inside the combustion chamber directly reflects the mileage of the vehicle, which is not desirable. To avoid this, adopting fuel injection technology becomes essential.

Types of Fuel Injectors

The advancement in fuel injection technologies gave rise to various fuel injection arrangements such as throttle body fuel injection, multi-point fuel injection, sequential fuel injection and direct injection that can be used according to the application.

On the Basis of Fuel Injection

On the basis of fuel injected injectors are of 2 types-

1. Diesel Fuel Injectors

These fuel injectors are used to inject or spray the diesel (which is heavier fuel than gasoline) directly into the combustion chamber of the diesel engine for further combustion by compression.

The capillary and nozzle of diesel fuel injectors are made to form diesel packets while spraying the fuel inside the combustion chamber.

Diesel fuel injectors require higher injection pumping than gasoline injectors as diesel is heavier than gasoline.

2. Gasoline Fuel Injectors

They are the fuel injectors used to inject or spray gasoline directly or through intake manifold into the combustion chamber for further combustion by spark.

The capillary and nozzle of gasoline fuel injectors is made smaller or same as the diesel fuel injectors depending upon the requirement.

As the gasoline is lighter than diesel, gasoline injectors required less injection pumping than diesel injectors.

On the Basis of Fuel Metering - Injectors

On the basis of fuel metering (controlling speed, quantity and pressure of the fuel) fuel injectors are of 2 types-

1. Mechanically Controlled Fuel Injectors

They are the fuel injectors in which the control of the fuel speed , quantity, timing and pressure is done mechanically with the help of spring and plunger. These parts take the input from the cam and fuel pump arrangement or by fuel distributor (advanced one).

2. Electronically Controlled Fuel Injectors

These fuel injectors are electronically controlled when it comes to fuel speed, quantity, pressure and timing. The electronic solenoid takes the input either from fuel distributor or from electronic control unit (advanced one) of the vehicle.

Construction of Fuel Injectors

The design of a fuel injector resembles a hose nozzle which is used to spray water over the ground grass. The same purpose is fulfilled by a fuel injector but the difference is instead of water fuel, injector spray fuel inside the engine. Let’s understand the construction of a fuel injectors by considering mechanically controlled fuel injectors and electronically controlled fuel injectors.

Mechanically Controlled Fuel Injector

Mechanically controlled fuel injectors are comprised of the following parts:

• Injector body–The outer body or “shell” inside which all the other parts of a injector are arranged. The inside of the injector body is to hold a precisely designed capillary or passage through which the highly pressurized fuel from the fuel pump can flow for further spray.
• Plunger –A plunger is used at the nozzle or narrow end of the fuel injector which is used to open or close the nozzle under the action of fuel pressure. It is governed by the fuel distributor or engine governor.
• Springs –Two springs are used inside the mechanically controlled fuel injectors. They are:

1. Plunger spring-The to-and-fro movement of the plunger is controlled by plunger spring which operates when the fuel pressure inside the fuel injector increases results in opening of the nozzle and returns to its initial position when the pressure decreases, which , closes the nozzle.
2. Main spring-The main spring is used to control the inlet of the fuel injector. The main spring operates under the action of fuel pressure provided by the fuel pump.

Electronically Controlled Fuel Injector

This is a smart type of fuel injector which is controlled electronically by the electronic control unit of the engine which is also known as brain of modern engines.

Electronically controlled fuel injectors consist of following parts:

• Injector body- Same as the mechanically controlled fuel injector the body of this type of injector is a precisely designed hollow shell inside which all the other components are arranged.
• Plunger-Same as the mechanically controlled fuel injector a plunger is used for the opening and closing of the nozzle but in electronically controlled fuel injector the opening of the nozzle is controlled electronically with the help of electromagnets.
• Spring –Same as the mechanically controlled fuel injector a plunger spring is used to hold the plunger in its position in order to close the nozzle of the fuel injector when required.
• Electromagnets –Unlike mechanically controlled fuel injectors, this type of injector is equipped with electromagnets just around the plunger which control the opening of the nozzle. This is done by taking the electronic signal from the electronic control unit of the engine through the electronic plug or connection connecting the fuel injector with the electronic control unit of the engine.
• Electronic plug/connection-At the top end of electronically controlled fuel injector a connection/plug is present through which the electronic signal from the electronic control unit of the engine is transferred to the electromagnets. This opens the nozzle in order to spray the fuel.

Working Fuel Injectors

Mechanically Controlled Fuel Injector

When the ignition of a vehicle is turned on to start the engine, the fuel pump of the engine start pumping the fuel to the fuel distributor which starts regulating the timing and amount of fuel to be sprayed.

• After the fuel distributor the fuel is transferred to the fuel injector according to the instruction of the fuel distributor through the fuel lines.
• In the fuel injector when this highly pressurized fuel reaches the fuel injector, due to its high pressure, this fuel pushes the inlet or main spring in order to enter the fuel injector.
• When this fuel enters the fuel injector it starts pushing the plunger spring which pushes the plunger outward and the opening of the nozzle takes place and sprays the fuel.
• When the spraying of the fuel for a particular cycle is completed according to the input given by the fuel distributor, the pressure inside the fuel injector decreases due to which the plunger spring retains its initial position. This results in the closing of the nozzle and the spray of the fuel stops for that particular cycle.

Electronically Controlled Fuel Injector

When the ignition of a vehicle is turned on to start the engine, the fuel pump along with the electronic control unit of the engine begin to:

• The fuel pump starts pumping the fuel to the fuel injector and then timing, the amount and pressure of the fuel entering the fuel injector is governed by the electronic control unit.
• The electronic control unit sends the electronic signal to the fuel injector with the help of the electronic connection. These electronic signals from the ECU electromagnets inside the fuel injector got activated which pushes the plunger outward and results in opening of the nozzle and finally the spray of the fuel.
• After completing this particular cycle, the electronic signal from the ECU stops which deactivates the electromagnets and causes the plunger to return to its initial position results in closing of the nozzle and the spray of the fuel stops.
• The closing of the nozzle is maintained by the plunger spring.