Difference Between the Spark Plug and Fuel Injector (Notes with PDF)

In this article, you’ll learn the differences between Spark Plug and Fuel Injector. After reading this article you can easily figure out the differences between these two. So let’s start with the definition of Spark Plug and 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

Here are some important points of the spark plug which you 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, Learn Mechanical

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 vapourised 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, Learn Mechanical

Difference Between the Spark Plug and 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 compression of air).
This component generates the spark with the help of DC current.This device compressed the diesel and sprayed the compressed fuel inside the engine cylinder.
In the case of Spark Plug, we need to maintain it on a regular basis, otherwise, carbon will be formed over the electrode and then we face engine starting problem.However for Fuel Injector, we don’t need regular maintenance like Spark Plug, but obviously we need to inspect Fuel Injector once a year.
In term of price point, Spark Plug is available comparably less price then Fuel injector.The Fuel Injector is a costly component.

So these are the difference between Spark Plug and Fuel Injector, I hope you are able to understand the difference between these. If you liked this knowledge-based article then do not forget to share this on your favourite social media platform, I hope to see you in further articles, till then stay happy and keep learning.

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  • All Images made by Saubhik Roy- Design Team Learn Mechanical
  • Feature Image modified by Author


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Anup Kumar Dey

A Mechanical Engineer with 19 years of working experience in various renowned MNCs.

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