5 Difference Between the Spark Plug vs Fuel Injector [PDF]

In this article, we shall learn the Differences between the Spark Plug vs Fuel Injector. We have provided a PDF for the same.

Differences between the Spark Plug vs Fuel Injector

What is a Spark Plug?

Spark Plug is a Mechanical component which is located at the top of the engine cylinder. The main function of a spark plug is to produce the Spark in the Combustion Chamber for ignition of charge inside the engine cylinder

These are some important points about the spark plug which we should know:

  • This device is located at top of the engine cylinder.
  • The proper location of the spark plug provides Correct timing for Ignition.
  • The main requirement of Spark Plug is, it must have high resistance and must have a proper gap between the two electrodes.
  • This Gap is usually between 0.6mm to 1mm.
Schematic Diagram of Spark Plug
Schematic Diagram of Spark Plug, Dizz

Purpose of Spark Plugs

  • Ignites fuel and air mixture in the combustion chamber
  • Transfers electrical energy from ignition system to combustion chamber
  • Provides heat dissipation from the combustion chamber
  • Helps to control the timing of the combustion process
  • Assists in maintaining engine performance and fuel efficiency.
Spark Plug

What is Fuel Injector?

The fuel injector is fitted inside the diesel engine. As you know in a compression ignition engine the pressurized fuel sprayed inside engine cylinder and due to the high temperature inside the cylinder the vaporized fuel burned and then the engine produced power stroke, so to control the amount of fuel and also the timing of fuel to sprayed inside the cylinder is maintained by the fuel injector.

Schematic Diagram of Fuel Injector
Schematic Diagram of Fuel Injector, Dizz

Purpose of Fuel Injector

  • Sprays fuel into the engine’s combustion chamber
  • Regulates the amount of fuel delivered to the engine
  • Improves fuel efficiency and reduces emissions by precisely controlling the air/fuel ratio
  • Enhances engine performance by providing consistent fuel delivery
  • Enables the use of alternative fuels, such as ethanol or biodiesel, by adjusting fuel delivery accordingly.
Fuel Injector

Difference Between the Spark Plug vs Fuel Injector

Spark Plug Fuel Injector
The spark plug is fitted on the Petrol Engine or SI Engine. (In a Petrol engine, the air-fuel mixture is sent into the engine cylinder and the mixture is ignited by the spark generated by the spark plug).The fuel injector is fitted on the Diesel Engine or CI Engine. (In Diesel engines don’t require any spark plug and the required heat to, Ignite the fuel is generated due to the compression of air).
This component generates the spark with the help of DC.This device compresses diesel and sprays this compressed fuel inside the engine cylinder.
In the case of the Spark Plug, we need to maintain it regularly, otherwise, carbon will be formed over the electrode and then we face an engine starting problem.However for Fuel Injector, we don’t need regular maintenance like Spark Plug, but we need to inspect Fuel Injector once a year.
In terms of price point, Spark Plug is available comparably less price than a Fuel injector.The Fuel Injector is a costly component.


In conclusion, although the spark plug vs fuel injector both of which are vital components in the combustion process of an internal combustion engine, they perform distinct functions. The spark plug is responsible for initiating the ignition of the air-fuel mixture, while the fuel injector precisely delivers fuel to the engine at the appropriate time and in appropriate amounts. Having a clear understanding of the Difference Between the Spark Plug vs Fuel Injector can aid drivers in identifying and resolving engine issues more efficiently, resulting in enhanced engine performance and efficiency.


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