Fuel injectors | Basics, Use, Construction, Working, Advantages and Disadvantages

Fuel injector working and construction details.

Fuel Injection or FI is the introduction of fuel in an Internal Combustion Engine by the means of an injector known as fuel injector. Fuel injectors are electronically controlled mechanical devices that are responsible for spraying (injecting) the right amount of fuel into the engine, so that a suitable air/fuel mixture is created for optimal combustion.

Why Fuel Injection?

Fuel Injection is used instead of carburetor because it offers:

  1. More power output.
  2. Better fuel efficiency.
  3. Reliability.
  4. Problem free cold starts.
  5. Better drive-ability and smooth engine operation.

More benefits includes smoother and crisper throttle response ( during quick throttle transitions),  more accurate adjustment to account for extremes of ambient temperatures and changes in air pressure, more stable idling and reduced maintenance needs.

Types of Fuel Injections:

The most common types of fuel injections are as follows:

1.Single point fuel injection:
Only one common injector is used in single point fuel injection which is located before the throttle and  injects the fuel for all cylinders. These types of injectors are usually with relatively lower impedance.

2. Multi point fuel injection (Commonly known as MPFI) :
This type of fuel injection system is used only in multi-cylinder engines. In multi point fuel injection one injector is used for one cylinder. The injectors are located after the throttle and are positioned so that they point at the back of the inlet valves. These types of injectors are usually with relatively higher impedance.


Fuel injection | Basics, Use, Construction, Working, Advantages and Disadvantages | Be Curious
Source: carssimplified
  • Fuel injection pump – pressurizes fuel to high pressure.
  • High-pressure pipe – sends fuel to the injection nozzle.
  • Injection nozzle – injects the fuel into the cylinder.
  • Feed pump – sucks fuel from the fuel tank.
  • Fuel filter – filtrates the fuel.
  • Return spring- to open close fuel passageway.
  • Fuel passageway- fuel flowing path.


Source: Wikipedia

Fuel Injection system uses ECU. The injectors are controlled by the Engine Control Unit (ECU). First, the ECU obtains information about the engine conditions and requirements like air pressure, air intake temperature, accelerator position, engine temperature, and engine speed using different internal sensors. These things happens within fractions of seconds.

These sensors feed information to ECU which processes these bits of data to compute the right amounts of fuel to be injected into engine cylinders. The valve on the injectors receive the  input from ECU so that it knows when to allow fuel to be squirted into inlet port.

Once the state and requirements of the engine have been determined, the fuel is drawn from the fuel tank, transported through the fuel lines and then pressurized with fuel pumps. Proper pressure is checked by a fuel pressure regulator. In many cases the fuel is also divided using a fuel rail in order to supply the different cylinders of the engine. Finally, the injectors are ordered to inject the necessary fuel for the combustion.

The exact fuel/air mixture required depends on the engine, the fuel used and the current requirements of the engine (power, fuel economy, exhaust emission levels etc.).


  1. All cars are using fuel injection system,
  2. Some commuter bikes (125-200 cc) and performance motorcycles( past 200 cc),
  3. Buses and trucks,
  4. Air crafts etc.


  1. More power output.
  2. Better fuel efficiency.
  3. Reliability.
  4. Problem free cold starts.
  5. Better drive-ability and smooth engine operation.
  6. Cleaner and greener emissions.
  7. Engine gives good throttle response as compared to carburetor.


  1. Complexity.
  2. Only professional mechanic with proper equipment’s can fix its problem, mean to say it might be difficult for a roadside mechanic to fix its problems without proper tools and knowledge.
  3. Expensive. Once fuel injection is implemented on bike the cost of bike goes high at-least Rs.12000. This is why smaller bikes (50-125 cc) are still equipped with carburetors.
  4. Although servicing is not required, but in case it has any problem then cost of servicing is more as servicing is not easy and might also need full replacement.
  5. Only supports good quality fuel.

Carburetor vs Fuel Injection

Both the devices have their advantages and disadvantages too. But considering everything fuel injection is best solution. Though it is quite expensive module and not repairable, but in future fuel injection will be adopted in every application of automobile and the cost will also come down. Moreover, world is moving towards lower emission and better fuel economy concerns so its better solution hence no disappointment in adopting fuel injection. There is no future of Carburetor as of now.

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