How Does a Diesel Fuel Injector Work?

an old off-white diesel machine

Diesel engines make use of the diesel fuel injector to pass fuel to the engine cylinders. A direct injection system is used, which means, that fuel is injected directly into the cylinders, thus the injector is of a vital nature. Nowadays this has become a rather sophisticated piece of engineering, making use of computer chips (ECM communications) to regulate the air intake, fuel spraying, RPM etc. Diesel engines normally are much more efficient than gasoline engines but not so long ago, diesel powered vehicles were associated with big and polluting trucks. It is true that diesel is great for large shipments but that’s not all, because today things started to change and the casual driver has grasped the fact that modern diesel engines are much cleaner and produce less noise.

How Fuel Is Passed

Fuel is pumped by a primary pump through a filter and then to the injection pump. There it is pressurized to 2300 - 3500 psi to each injector.

The Injector Device Itself

The fuel injector is controlled by the ECU with the help of various sensors. The ECU makes the appropriate calculations to determine, for example, the air intake and fuel injection, amongst other functions. The injector makes use of a solenoid that is normally opened so that vaporized diesel can pass (the duration of this process is called the pulse width). Each injector present on each cylinder receives different amounts of fuel, calculated by the ECU. The latter will allow to the combustion process to reach the ideal stoichiometric ratio (air, fuel and ignition mixed together). The injector device has a small pump attached to it which is used to force air into the injector, mixing with the fuel, hence the device has to be able to resist high temperatures and high amounts of pressure. The device uses a small nozzle to spray diesel into the combustion chamber. The nozzle has a sequence of small holes so that fuel is distributed accordingly into the cylinder. The system makes use of another valve to suck air from the chamber which is mixed with vaporized diesel to intensify the combustion process.

The Final Step

Finally the exhaust valve removes any emissions present in the combustion chamber whilst the return fuel line removes any remaining fuel present in the chamber and returns it to the fuel tank.

Types of Diesel Engines

Some diesel engines may have a glow plug. A glow plug is that piece of equipment that heats up the combustion chambers to raise the temperature because sometimes the engine doesn’t rise to the required temperature for proper combustion, due to cold weather. Today large engines do not use glow plugs. Instead, all of the work is done by the ECM which reads the ambient temperature and retards the spraying of diesel into the cylinders accordingly. However, glow plugs are still an alternate system to raise temperature on smaller diesel engines.