What is the difference between a glow plug and a spark plug? These two car parts sound similar, but they each serve their own purpose. Knowing which is which can help you understand your vehicle’s performance and maintenance needs. If you’re thinking long-term about your vehicle’s health, an extended motor warranty can go a long way to cover costly repairs.
What Is a Glow Plug?
Glow plugs are heating devices used in diesel engines to help with starting, especially in cold weather. They work by warming the air in the combustion chamber to a temperature high enough to ignite fuel.
Its Role in Diesel Engines
Diesel engines rely on compression to ignite fuel, not a spark, like petrol engines. In cold conditions, the air-fuel mixture might not reach a high enough temperature to ignite on its own. Glow plugs act like little toasters inside your engine, heating things up quickly to get your car started smoothly.
How Glow Plugs Operate
Glow plugs are switched on when you turn the key (or press the start button), and they begin to heat the combustion chambers. Once the engine is running, they usually switch off, although some modern vehicles keep them running briefly to reduce emissions and ensure efficient operation.
What Do Spark Plugs Do
If you drive a petrol-powered car, you’ll be more familiar with spark plugs. They’re essential for starting and running your engine.
Spark Plug Function in Petrol Engines
Unlike diesel engines, petrol engines need a spark to ignite the air-fuel mixture. That’s exactly what spark plugs do. They deliver a small, high-voltage jolt of electricity to create a spark that kicks off combustion.
Spark Plugs vs Glow Plugs
While both parts live in the engine and are involved in combustion, they’re used in entirely different types of engines. Here’s a quick side-by-side:
|
Feature |
Spark Plug |
Glow Plug |
|
Engine Type |
Petrol |
Diesel |
|
Function |
Creates spark to ignite fuel |
Heats chamber to aid ignition |
|
Activation |
During engine start & run |
Primarily during cold starts |
|
Failure Symptoms |
Misfires, rough idling |
Hard starts, white smoke |
Signs of Failing Glow Plugs and Spark Plugs
- Glow Plug Issues: If your diesel engine takes forever to start, especially on chilly mornings, your glow plugs might be on their last legs. Other signs include white smoke from the exhaust and poor fuel efficiency.
- Spark Plug Problems: Misfiring, engine knocking, a rough idle, and decreased acceleration can all point to worn-out spark plugs.
Effects on Vehicle Performance
Neglecting these parts can lead to sluggish performance, higher fuel consumption, and even permanent engine damage over time. That’s why recognising early signs of failure is so important.
Protect Your Engine & Your Pocket
Understanding the basics of how car components work is important to keep your vehicle running at its best. And while you can manage some maintenance yourself, bigger issues can become expensive. That’s where a worry-free extended motor warranty can give you peace of mind.
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