Do diesel engines have spark plugs?

Q: Do diesel engines have spark plugs?

A: No, diesel engines do not have spark plugs.

What are spark plugs? What do spark plugs do?

Spark plugs are located at the top of the cylinder head in petrol-fuelled internal-combustion engines. 

As the name implies, these engines rely on the combustion process to power the engine. 

And a spark plug – as the name implies – is an electrical component which produces a spark that ignites the petrol-air mixture, causing the combustion process to kick off in order to power the engine. That spark is created between two electrodes at the tip of the plug as a result of a high-voltage charge received via the ignition coil at the other end of the spark plug.

What kinds of cars have spark plugs?

Spark plugs are found in cars with petrol engines.

Do diesels have spark plugs?

No, they don’t.

How many spark plugs are in a diesel?

None, but they do have glow plugs which we’ll get to in a couple of sentences below this. Most diesel engines run on one glow plug per engine cylinder.

Why don't diesel engines have spark plugs?

Because diesel engines use high compression, rather than an actual spark, to ignite the fuel. Air is drawn into the engine cylinder and compressed to an extremely high pressure and consequent temperature.

What do diesels have instead of spark plugs?

Glow plugs.

What do glow plugs do in a diesel engine?

As mentioned above, diesel engines use high compression, rather than an actual spark, to ignite the fuel. 

So, instead of spark plugs, diesel engines use glow plugs, electrical heating devices located in each cylinder of the diesel engine, which preheat the air in the engine’s cylinders to expedite the combustion process necessary to start the engine.

A glow plug in a diesel-fuelled vehicle is only needed during the ignition process, whereas a spark plug in a petrol-fuelled vehicle works continuously while you’re driving.

Do all diesels have glow plugs?

No, not all diesel engines have glow plugs.

When the diesel-air mixture is compressed quickly in a diesel engine, it ignites without any need for an actual spark and that produces heat enough to kick-start the combustion process.

But smaller diesel engines have difficulty maintaining the temperature necessary for combustion and the purpose of glow plugs is to warm the diesel-air mixture in order for it to combust of its own accord.

Many larger diesel engines don’t need any glow plugs because their diesel-air mixture ignites without any need for assistance. . The diesel-air mix has sufficient heat coming from the air, which becomes increasingly hotter as it is quickly compressed.

How does a diesel engine work?

This is best explained by a panel of diesel experts over at Cummins who came up with this nifty explanation … and it reads like poetry to me:

“In general, a diesel engine works by using a piston to compress air to increase the temperature in the cylinder and then injecting atomised diesel fuel into this cylinder.

“When the fuel comes into contact with the high temperature, it ignites, creating energy that drives the piston down transferring energy to the crankshaft and through the powertrain.

“This process is repeated over and over again at a high speed, making a diesel engine a powerful piece of technology. 

“Different types of diesel engines will have varying compression ratios. The compression ratio of the diesel engine impacts how much power the engine puts out. The higher the ratio, the more power is generated.”

Couldn’t have said it better myself.