How Does a Diesel Truck Engine Work?

The modern diesel engine is much more powerful and efficient than the original. Today, they are built to withstand the rigors of higher compression and increased performance standards. Because of that, they’ll function longer than previous models before needing any tune-up or repairs. Diesel engines’ longevity is the main appeal for its fans. The increased torque and power output by the engines lead to increased towing power. That’s why all heavy machines and tractor-trailers have a diesel power plant—they can do a lot of work. Light-duty pickup trucks that have diesel engines, combined with an Allison 1000 transmission, have more power and torque than their gasoline counterparts. So, how does a diesel truck engine work? Let’s take a look.

Fuel Ignition

The fuel in diesel engines is ignited through compression, unlike a gasoline engine, which relies on a spark plug to ignite the fuel. A piston within the engine compresses the air in the cylinder, making it extremely hot. Once the air is heated, fuel injectors atomize the diesel fuel and inject it into the hot cylinder. The hot air instantly ignites the fuel, creating ignition—the energy needed to initiate the combustion process. The ignition causes the diesel to burn with oxygen from the atmosphere. That contained explosion causes the piston to be pushed back out. This process carries out again and again, with all the pistons firing in unison. The pistons connect to the crankshaft, and as they move in and out, the crankshaft turns.

The crankshaft connects to the flywheel at one end, and to the camshaft at the other. The flywheel regulates the power of the crankshaft, similarly to a surge protector.

Diesel Fuel

Starting a diesel engine on a cold day is difficult. Diesel owners must go to great lengths to keep the engines warm, so they don’t freeze up. The reason for that is the way that diesel engines ignite the fuel. The starter motor must be strong enough to compress the air inside the cylinders and ignite the fuel and air mixture. Diesel fuel has a freeze point of 32 degrees Fahrenheit, which is much higher than gasoline’s. When the temperature is around 32 degrees, the fuel will start to crystallize, turning murky and cloudy, signifying it’s about to freeze. At around 10 to 15 degrees, the liquid paraffin wax in the fuel will start to gel. When that happens, the fuel can’t flow or inject into the cylinders—meaning, the engine won’t start.