It’s a fairly basic process. To begin, air is pumped into the cylinders. Then, pistons compress the air between 14 and 25 times, producing heat. Once the air is compressed, the fuel injectors spray diesel fuel into the cylinders. Introducing the diesel fuel to the hot air causes the mixture to ignite, producing chemical energy. The combustion pushes the piston back out of the cylinder, which transforms the chemical energy into mechanical energy. This process repeats hundreds to thousands of times a minute to produce enough energy to power a vehicle.