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Electronic Fuel Injection: Definition, Types, Principle, and Components

What is Electronic Fuel Injection?


Electronic Fuel Injection is a fuel spray system that works electronically controlled so that the mixture of air and fuel is always following the needs of the fuel motor.

electronic-fuel-injection-part


Thus the combustion process in the combustion chamber will occur perfectly to obtain optimal motor power and environmentally friendly exhaust gases. The method of fueling the ECU (Electronic Control Unit) to the injector is based on signals from sensors, such as:


  • engine speed sensor

  • water temperature sensor

  • airflow meter sensor

  • absolute pressure manifold

  • Throttle position sensor, etc.

Electronic Fuel Injection Working Principle


The electronic fuel injection system is separated into sensors and actuators. Sensors act as providers of information about conditions related to determining the amount of petrol that must be injected. The provision of that information can be either analytical or digital signals. Examples of sensors that send data in analog form are mass airflow and Throttle Position Sensor (TPS).


efi-system
EFI system


While the actuator is a component whose operation is regulated by the ECU in an analog or digital way, analog commands are given to the electric gas pump and engine control lights. In contrast, digital signal commands are given to the injector, ignition coil, tank breather valves, idle regulator, and lambda sensor heaters.

Electronic fuel injection VS Carburetor


The following is the difference EFI and carburetor system when the car engine temperature is cold and during acceleration.

The Carburetor System


In the carburetor system, the petrol supply when the car engine is cold will be regulated by minimizing the amount of air intake.
carburetor-system
Carburetor system


Thus, the fuel will come out richer, and the arrangement is made by a choke circuit that works automatically or mechanically. Furthermore, the fuel supply is regulated by the value of the engine vacuum level—the greater the value of the vacuum, the greater the supply of fuel to be provided.

carburetor-system-during-engine-accelaration
Carburetor system during acceleration


The acceleration circuit will provide the gas supply in the carburetor system during acceleration. The acceleration circuit is carried out by a lever connected to a tilt arm.

Meanwhile, the tilt arm is driven by throttle valve acceleration, and then the gasoline will come out through the pump jet toward the venture.

The EFI System


In the EFI system, fuel supply when the engine is cold will be determined by the ECU (Electronic Contro Unit) based on information from engine operating temperature conditions and the value of air pressure at the intake manifold.

efi-system-during-engine-acceleration
EFI system during engine acceleration

The fuel supply during the engine accelerates regulated by the ECU based on information on the amount of air flowing through the intake manifold measured by the airflow meter. From this data, the ECU will instruct the injector to add gasoline to be injected.

Electronic Fuel Injection System Types and Components


EFI system is divided into two types, namely Type D and L.

EFI Type D


In EFI type D, the measurement of air entering the intake manifold is carried out by a vacuum sensor.

efi-type-D
EFI type D

The pressure value in the intake manifold is used as information for the ECU. Also, it used as a determinant of the amount of gasoline to be injected.

EFI Type L


In EFI type L, the value of air entering the intake manifold is measured using airflow meter, is used as information for the ECU as a determinant of the amount of petrol to be injected.

EFI type L

EFI Components


The following are Electric Fuel Injection components and their functions.


  1. Fuel pump: Suck fuel from a tank and press it to the delivery line to be ready for injection
  2. ECU: Processing data received from sensors and giving commands to components to operate.
  3. Speed Sensor: Detects vehicle speed
  4. Data Link Connector: Diagnose the working of the system
  5. Variable Resistor: Adjusts the fuel and air mixture level
  6. Throttle Sensor: Detects the size of the gas valve opening
  7. Pressure Sensor: Detects/measures the amount of pressure in the intake manifold
  8. Idle Speed Control: Adjust engine idle speed
  9. Injector: Receives an order to inject a certain amount of fuel
  10. Cam Angle Sensor: Knowing the size of the cam angle
  11. Crank Angle Sensor: Detects high or low engine speed
  12. Knocking Sensor: Detects engine knock
  13. Temperature Sensor: Monitor high and low water temperatures

Fuel Pump


Fuel pumps commonly used on engines with EFI systems are electric gas pumps that function to suck fuel from the tank and press it into the fuel system.

The pumps that are commonly used are "in-tank" and "inline" types. In-tank type means the fuel pump is in the tank submerged in petrol. While the type inline means the fuel pump is outside the fuel reservoir.

In the series, the work of the petrol pump is monitored by the ECU. So, if the transistor on the ECU is OFF, then the electric current does not flow into the mass. Thus, the pump relay is off. As a result, the electric current from the battery does not go to the pump, and the pump cannot work.

Electronic Control Unit


Electronic Control Unit is a component of the fuel system that receives electrical signals from sensors. Furthermore, the sensor is processed into a command line to the actuator.

electronic-control-unit
Electronic Control Unit


The ECU gets the mains supply from the battery and is forwarded to the sensor and actuator. The voltage value is adjusted to the capacity of the sensor or actuator.

Explanation of ECU Parts and their functions

  • Micro Processor: Set the order and make decisions about data that has been treated based on information from data storage in system memory.

  • Memory: Store input data that is ready to be informed to the microprocessor

  • Input: provides information in the form of an electrical signal to memory for processing by a microprocessor.

  • Data Acquisition: Data data that has been treated by a microprocessor is distinguished and then informed to the output

  • Output: The electrical signal generated by the data acquisition given to the actuators

Data Link Connector


Data Link Connector is a collection of codes to facilitate the detection of work from sensors or actuators. DLC is applied to all vehicles with EFI systems as a connector to diagnose the working system through certain software. To detect it manually is by jumpers codes with other codes under the manual book of each vehicle or brand of the car.

Variable Resistor


The variable resistor functions to regulate the fuel mixture at idle speed. Adjustment aims to produce the correct co value, so do not adjust the variable resistor without using a CO tester.
Adjustment

If the fuel mixture is excessive, change the variable resistor by turning the adjusting screw with SST clockwise. Meanwhile, if the adjusting bolt is turned counter-clockwise, it indicates that the fuel is too lean.

Throttle Sensor


The throttle sensor will detect the amount of gas valve opening. The movement of the gas valve will move the slider or friction arm, which affects the value of the resistance. The ECU will determine the quantity of gasoline that will be injected based on this information.

The throttle sensor is fitted on the throttle body, which detects the opening angle of the throttle valve. When the throttle valve is fully closed, a voltage of 0.3 +- 0.8 Volt will be provided by the ECU through the VTH / VTA terminal.

Meanwhile, if the throttle valve is open, the voltage from the ECU to VTH / VTA will increase according to the throttle valve opening angle. The voltage value becomes 3.2 to 4.9 volts when the throttle valve is open. The ECU considers driving conditions based on the input signal and uses it to determine the correct air-fuel ratio, power gain, and fuel cut control.

Pressure Sensor


A pressure sensor is attached to the intake chamber to detect the condition of the air pressure at the intake manifold. The pressure value at the intake will be informed to the ECU as an analog input.

pressure-sensor
pressure sensor


Idle Speed Sensor


Idle speed control is fitted on the lower part of the throttle chamber and serves to regulate the amount of air given at idle rotation. The ECU only operates the ISC valve to make idle ups and provide feedback to achieve the idling rotation target.

Injector


The injector is one part of the fuel system so that a homogeneous mixing process between air and fuel becomes possible. Injectors have plungers that can open or close fuel lines.

injector-in-electronic-fuel-system
EFI injector


Based on instructions from the ECU engine, the solenoid controls the work of the plunger. More fuel will come out if the plunger holding time is longer and vice versa. The settings for the excess fuel mixture, lean, and injection time depend on the signal sent by the ECU engine.

Cam Angle Sensor


The cam angle sensor is mounted on the upper side of the cylinder head to detect any change in the cam angle movement. The sensor will notice changes in the camshaft angle associated with the inlet valve. Furthermore, the signal is considered by the ECU to start fuel injection or end it.

Crank Angle Sensor


Crank Angle Sensor will detect engine speed and piston location of every cylinder.

Temperature Sensor


Water temperature sensor functions to detect the condition of the cooling water heat, and it is installed in the engine block or at the bottom of the thermostat housing. The sensor will work according to the resistance value. The higher the temperature of the cooling water, the smaller the resistance and vice versa.

The cooling water sensor is linked to the ECU engine, which provides a 5 Volt power source voltage to the sensor via a resistor from the THA / THW terminal.

When the resistance value changes according to changes in the temperature of the cooling water, the potential at the THA / THW terminal will also change. Following these signals, the ECU changes the fuel injection volume to maintain engine performance during operation.

Knocking Sensor


The knocking sensor will detect the symptoms of knocking on the engine because if it takes place in the combustor, the ECU will set the ignition more forward or backward to eliminate knocking.

Electronic Fuel Injection Classifications

According to the Fuel Spray Area


Based on where the gasoline is sprayed, the EFI system is divided into direct and indirect injection.
Direct injection: The injector injects the gasoline straight into the burning chamber.

In contrast, indirect injection: The fuel is not instantly injected into the combustor but through the intake manifold.

According to the Fuel Spraying Rhythm

  • Simultaneous Model


The simultaneous spraying rhythm means that the gasoline is injected into the firing chamber continuously. Or in other words, fuel spraying does not take into account the working conditions of the engine. Spraying simultaneously on all cylinders per one crankshaft rotation (360 degrees).

  • Model Grouping


In the spraying rhythm of the grouping model, petrol is injected into the burning chamber continuously following the cylinder group.
Fuel spray takes into account the condition of the engine working steps. Spraying simultaneously on all cylinders every 720 degrees or two full rotations of the crankshaft.

  • Sequential Model


In the sequential spraying rhythm, gasoline is injected into the combustor continuously following FO (Firing Order). Fuel spray takes into account the working conditions of the engine and simultaneously on all cylinders every two crankshaft turns (720 degrees).

According to the Fuel Spraying Service


There are two models of spraying fuel into the intake manifold, namely single point injection and multi-point injection.

Single Point Injection (SPI)


In this model, fuel spraying will be done by an injector that is in the intake manifold before the throttle valve. The injected fuel will be sucked in according to the work of each cylinder engine. One injector serves all cylinders, and this is almost the same as a conventional fuel system.

single-point-injector
Single Point Injector


The mixture of fuel and air in the intake manifold will wait for the inlet valve to open. As a result, it causes deposition along the intake manifold and becomes a disadvantage to the single-point injection system.

Model Multi-Point Injection (MPI)


The point of spraying fuel is in each inlet into the cylinder. Thus, the efficiency of fuel intake per cylinder is better.

multi-point-injection
Multi-Point Injection

Based on the construction of the control system, the EFI system is divided into:

  • mechanical injection

  • Electronic Mechanical Injection

  • electronic injection

  • engine management system.

Mechanical Injection


In this system, the fuel-injected occurs mechanically, where the throttle valve movement will regulate the amount of air needed by the engine and move the lever. Then the lever pushes the fuel gauge lever to determine the amount of fuel to be injected.

Electronic Mechanical Injection


The electronic, mechanical fuel injection system has an electronic regulating system called the electronic control unit. The control system is limited only at the time of injection. Concurrently, the quantity of fuel that must be injected will be determined by the mechanical movement of the fuel control arm (mixture control unit).

Electronic injection


EFI is a system of supplying fuel requirements where the amount and time of supply are regulated electronically by the ECU engine. The ECU engine will process data informed from sensors and will be taken into consideration to determine the time and amount of fuel that must be injected.

Engine Management System


The engine management system is an electronic fuel injection system where the ignition system is regulated in 1 unit with the ECU engine. In other words, the ignition system is not separate from the ECU engine.

Electronic Fuel Injection Troubleshooting


Car engine won't start

Check Components:
  1. Immobilizer
  2. Crankshaft position sensor
  3. Amount of fuel and fuel filter condition
  4. Fuel pump and connection
  5. A leak or air intake-vacuum system condition
  6. absolute sensor manifold
  7. Injectors
  8. camshaft position sensor
  9. connector, cable, and relay ECM
  10. ECM
  11. Electricity-engine / battery connection
  12. Ignition system
  13. Fuel pressure and fuel regulator
  14. Engine coolant temperature sensor

Car engine hard to start

Check Components:
  1. The amount of fuel and the condition of the gasoline filter
  2. Fuel pressure and fuel regulator
  3. Leakage of air intake-vacuum system conditions
  4. Electric-engine / battery connection
  5. Engine coolant temperature sensor
  6. Throttle position sensor
  7. Injectors
  8. Camshaft position sensor
  9. Ignition system
  10. Crankshaft position sensor
  11. connectors, cables, and ECM relays
  12. ECM
Ryan Daniel
Ryan Daniel Ryan Daniel is a car enthusiast. Since owning his first BMW at a young age, he has loved the automotive world even more.