Though diesel engines and gasoline engines are each internal combustion engines, from there the similarity essentially ends. Both engines ignite a fuel/air mixture that delivers an explosive force to drive a crankshaft, thereby powering, for instance, the wheels of an automobile. The method of fuel ignition, however, is far different between the two engines, with the diesel fuel pump being crucial to this ignition.
Diesel fuel is heavier than gasoline, and not quite as volatile. Also, diesel fuel evaporates more slowly than does gasoline. The popularity of diesel engines is, in large part, a result of the energy density of diesel fuel, which is considerably higher than the density of gasoline, resulting in better energy efficiency. The diesel engine, unlike gasoline engines, does not use a spark to ignite the fuel/air mixture. The heat of the compressed air in the cylinder of the diesel engine provides the ignition source, thus, eliminating the need for spark plugs.
A diesel fuel pump, often called a diesel fuel injection pump must, therefore, inject fuel directly into the cylinder. The diesel fuel is ignited when it comes in contact with the super-compressed, super-heated air inside the cylinder. Sometimes, the diesel fuel injection is helped along by compressed air being injected as a boost to the fuel injection process.
The diesel fuel pump is a fairly complex and sturdy mechanism. In fact, it is the most complex diesel engine part. Additionally, a diesel fuel pump must be durable enough that it can withstand the pressure of the compressed air, and the heat of the injection process. The fine mist of fuel needed for the proper ignition must be maintained by the diesel fuel pump under these extreme conditions.
Diesel fuel pumps may be located just about anywhere on the engine, depending on the manufacturers design. Much experimentation has been done over the years regarding the most effective placement of the diesel fuel pump. So far it seems that so long as the pump is mounted on the engine, it will effectively deliver fuel to the cylinders. A gasoline fuel pump, on the other hand, may be mounted anywhere in the engine compartment or along the fuel distribution system.
Depending on the location and design of the diesel fuel injector pump, pre-combustion chambers, customized induction valves, and other systems are often used in the injection process. These injection enhancers often aid in circulating, or swirling the air inside the cylinder for more efficient combustion. Just as with any engine fuel injection system, diesel fuel pumps are constantly being improved to be more efficient and less costly.