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Fuel Injection System: Diagram, Parts, Working, Types [PDF]

In this article, you’ll learn what is fuel injection system? Its diagram, parts, working, advantages, and applications all are explained with pictures.

Also, you can download the PDF file at the end of this article.

What is Fuel Injection System?

A fuel injection system is a type of internal combustion engine system that uses fuel injectors to deliver fuel in a precise and controlled manner to the engine’s combustion chamber or cylinders. This ensures efficient combustion by atomizing fuel and injecting it under high pressure at the correct time into engine cylinders.

Carburetors were widely used on engines before fuel injectors were invented, and this engine is still in use today. In reality, many other machines still use carburetors, including lawnmowers and chainsaws. Due to the complexity of controlling all automobile requirements, fuel injection was released as a better alternative.

Fuel injection systems come in many different varieties, but they all share some basic parts. These parts include a fuel pump, a fuel injector, a fuel pressure regulator, and an electronic control unit (ECU) that manages the system’s operation.

Today’s vehicles use fuel injection systems to increase fuel efficiency, reduce emissions, and increase performance. In order to meet pollution standards and enhance engine performance, they also enable greater control over the air/fuel mixture.

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Parts of Fuel Injection System

A fuel injection system is a complicated system comprising several important parts. A fuel injection system’s essential components are:

  1. Fuel tank
  2. Fuel pump
  3. Injection pump
  4. Fuel filter
  5. Governor
  6. Fuel pressure regulator
  7. Fuel injectors
  8. Throttle body
  9. Engine control module (ECM)
Parts of Fuel Injection System

#1 Fuel Tank

The fuel tank serves as a reservoir for the fuel supply, helping to keep its temperature below the flash point. Additionally, the fuel tank plays a crucial role in dissipating heat from the fuel that is returned from the engine.

#2 Fuel Pump

Fuel is transferred from the fuel tank to the fuel injectors by the fuel pump. Electric or mechanical fuel pumps are both available. The purpose of the fuel pump is to keep the fuel pressure constant.

#3 Injection Pump

The mechanism that injects fuel into a diesel engine’s cylinders is known as an injection pump. A toothed belt (often the timing belt) that also drives the camshaft is used to drive the injection pump indirectly from the crankshaft.

#4 Fuel Filter

A fuel filter reduces the amount of dirt, debris, and other contaminants reaching the fuel injectors and helps prevent the fuel from becoming contaminated. A clogged fuel filter can reduce engine performance and even cause fuel injection system damage.

#5 Governor

The governor’s function is to regulate the fuel to the engine cylinders in order to control the speed of the unit, holding the speed constant for all conditions of load forced on the generator being driven by the engine.

#6 Fuel Pressure Regulator

The function of the fuel pressure regulator is to control the fuel pressure and guarantee a steady flow of fuel to the engine. It helps to ensure that the fuel pressure stays within a predetermined range.

#7 Fuel Injectors

The parts that deliver the fuel to the engine’s combustion chamber are known as fuel injectors. Fuel is sprayed into the engine by the fuel injectors at high pressure and in a precise pattern.

#8 Throttle Body

A throttle body is a part of the engine that controls how much air is allowed to enter the engine. Normally, it’s situated halfway between the air filter and the intake manifold.

#9 Engine Control Module (ECM)

The fuel injection system’s ECM is referred to as its brain. The fuel and air mixture, fuel injection timing, and other parameters are adjusted by the ECM using input from various sensors to enhance engine performance and fuel economy.

Read Also: Understanding the Working of Distributorless Ignition System

Function of Fuel Injection System

An engine fuel injection system ensures efficient combustion and optimal performance by delivering fuel in a controlled and precise manner based on the engine’s operating conditions. Typically, it consists of an electronic control unit, a fuel pressure regulator, fuel injectors, and a fuel pump (ECU).

Working of Fuel Injection

A fuel pump pressurizes the fuel and delivers it to the fuel injectors. Injectors deliver fuel to the combustion chamber of engines. The fuel pressure regulator keeps fuel pressure within a specific range, while the ECU analyzes engine load, RPM, and temperature to determine the best fuel delivery.

By modifying the fuel’s quantity, timing, and pattern of injection, the fuel injection system regulates the fuel’s delivery. As a result, the air-fuel mixture can be precisely controlled, ensuring efficient combustion and producing the best engine performance, fuel efficiency, and emissions reduction.

The type of system being used affects the specific function of the fuel injection system. For instance, a port fuel injection system delivers fuel to the intake port, while a direct injection system delivers fuel directly to the combustion chamber. Its overall purpose is to deliver fuel accurately and efficiently to the engine to optimize performance and efficiency.

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Types of Fuel Injection Systems

Fuel injection systems come in various types, each with special qualities and benefits. Listed below are a few of the most typical fuel injection system designs:

  1. Single-point or throttle body injection (TBI)
  2. Multi-point fuel injection (MPI)
  3. Direct injection (DI)
  4. Sequential fuel injection
  5. Dual injection system

#1 Single-point or Throttle Body Injection (TBI)

Single-point or Throttle Body Injection (TBI)
Image: Spinny.com

The earliest fuel injection system to replace carburetors was the single-point type. Older cars frequently have this type of fuel injection system because it is the simplest. A single fuel injector is found on the throttle body, which is mounted on top of the intake manifold.

The throttle body receives the fuel spray from the injector, which mixes it with the incoming air before delivering it to the engine. It consists of one or two injector nozzles in the engine’s throttle body, which is the air intake manifold’s throat. While injectors are not as precise as carburetors, they have better control, are less expensive, and are easier to maintain.

#2 Multi-point Fuel Injection (MPFI)

Multi-point Fuel Injection (MPFI)

Multiple fuel injectors are used in a multi-point fuel injection system, and they are positioned at the intake ports of each cylinder. This system enables better engine performance and more exact control over the fuel mixture.

This system uses multiple ports on each cylinder’s intake valve to inject fuel into internal combustion engines. It precisely and timely distributes the right amount of fuel to each cylinder. MPFI systems can be classified as Batched, Simultaneous, or Sequential. Modern automobiles and other vehicles frequently use it.

#3 Direct Injection (DI)

Direct Injection (DI)

Instead of the intake manifold or throttle body, direct injection (DI) injects fuel directly into the engine’s combustion chamber. This system enables more exact control over the fuel mixture, which may enhance engine performance, increase fuel efficiency, and lower emissions.

These are typically managed by an electronic control unit (ECU) that determines the best fuel delivery using information from various sensors. Direct fuel delivery to the combustion chamber allows for optimizing the fuel mixture for various engine conditions, such as high load or low-speed operation.

#4 Sequential Fuel Injection

Sequential Fuel Injection

In a sequential fuel injection system, fuel is delivered in a specific order to the engine’s cylinders based on the engine’s firing order. When the engine is idling, the fuel can stay for as long as 150 milliseconds because they all spray at the same time or in succession.

Sequential fuel injection has the advantage of allowing the engine to react more quickly to sudden driver changes. This is due to the fact that the valve doesn’t need to wait for the engine to turn completely; instead, it only needs to wait for the following intake valve to open.

#5 Dual Injection System

Dual Injection System
Image: premierautotrade.com.au

The dual fuel injection system was developed to overcome the drawbacks of both port and direct injection systems. This system primarily relies on the port fuel injector at low RPMs because it produces a better air-fuel mixture. This assumes that the engine will benefit fully from port fuel injection.

As the RPM increases, the direct injector takes over, and the port injector shuts off. Since the direct injection system is quicker at higher RPM and may perform better, this improves combustion efficiency.

The port injector helps when the direct port injector cannot provide enough fuel at such high speeds as the RPM increases. At high RPMs, both injectors will work together to supply fuel to the cylinder.

Read Also: Understand The Working of Wankel Rotary Engine

Symptoms of Fuel Injection System

A malfunctioning fuel injection system frequently produces a number of symptoms, such as:

  1. Decreased Fuel Efficiency: A malfunctioning fuel injection system can result in the engine using more fuel than necessary, lowering fuel efficiency and raising fuel consumption.
  2. Rough Idling: The engine may idle rough or erratically due to a failing fuel injection system, which can be felt as vibrations or shaking inside the car.
  3. Engine Misfires: When the fuel injection system isn’t working properly, the engine may misfire or run unevenly, which can be noticed as a loss of power or a stutter when accelerating.
  4. Starting Problems: The engine may be difficult to start or require several attempts if the fuel injection system goes wrong.
  5. Stalling or Hesitation: When accelerating or driving, an engine may stall or hesitate due to a broken fuel injection system.
  6. Check Engine Light: The check engine light may come on due to a failing fuel injection system, which could be an engine or emissions system issue.
  7. Reduced Engine Power: A failing fuel injection system may result in the engine losing power or not running as efficiently as it should.

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Advantages of Fuel Injection System

Compared to conventional carbureted engines, fuel injection systems have a number of benefits.

The following are some of the main benefits of fuel injection systems:

  1. Compared to carburetors, fuel injection systems deliver fuel more precisely and under greater pressure, allowing the engine to operate more effectively.
  2. The air/fuel mixture can be more precisely controlled, which can improve engine performance, smooth out acceleration, and lower emissions.
  3. This system can help lower harmful emissions like carbon monoxide, nitrogen oxides, and particulates.
  4. Fuel injection systems can facilitate cold starts by automatically adjusting the air/fuel ratio to compensate for low temperatures.
  5. Compared to carbureted engines, fuel injection systems are typically more serviceable and require less maintenance.
  6. Modern performance motorcycles can use this system.
  7. This system lessens spark plug fouling problems and reduces engine vibration.

Disadvantages of Fuel Injection System

While fuel injection engines have a number of benefits over conventional carbureted engines, there are also some potential drawbacks to be aware of.

The following are some disadvantages of fuel injection systems:

  1. Since diagnosing and fixing fuel injection systems requires specialized knowledge and equipment, they are more complicated than carbureted engines.
  2. Generally, the cost of manufacturing and installing fuel injection systems is higher than for carbureted engines.
  3. Electronic parts like sensors, actuators, and control modules are necessary to operate fuel injection systems. There is a chance that these parts will malfunction.
  4. In order to function properly, it needs clean fuel. The fuel injectors may clog if the fuel is polluted with debris, water, or other contaminants.
  5. Compared to carbureted engines, fuel injection systems can be more challenging to diagnose.

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Applications of Fuel Injection System

There are many different applications for fuel injection systems, some of which are listed below:

  1. In order to increase fuel efficiency, lower emissions, and improve engine performance, fuel injection systems are frequently used in modern automobiles.
  2. To increase engine performance and efficiency, many modern motorcycles also use fuel injection systems to supply fuel to the engine.
  3. These systems are used in airplane engines to give precise fuel mixture control and enhance engine performance at high altitudes.
  4. Marine engines, such as those found in boats and ships, use fuel injection systems to improve fuel efficiency and performance.
  5. Additionally, a wide variety of industrial engines, such as those found in generators, agricultural machinery, and construction equipment, use fuel injection systems.

Closing It Up

That’s it. Thanks for reading. I hope I have covered everything about the “Fuel Injection System.” It would be helpful if you could let me know if there was anything I missed or if you have any doubts about anything I wrote. Please share this article with your friends if you find it interesting.

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External Links:

  1. https://en.wikipedia.org/wiki/Electronic_control_unit
About Yousef

He is a mechanical engineering student, he likes to write about engineering stuff and he is really interested in learning about new technology in machines.

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