What happens to the fuel after it is raised by the pump?

The injection pump "or injection pump" is a device capable of raising the pressure of a fluid , usually present in systems of fuel injection as diesel (Diesel Engines) or more rarely petrol (gasoline), to a level at high enough that when it is injected into the engine it is sufficiently pulverized, an essential condition for its spontaneous inflammation (basis of the diesel engine cycle ), thanks to the high self-combustion temperature.

They also distribute the fuel to the different cylinders according to their order of operation (eg 1-3-4-2 in the 4 cylinders). Basically there have been two types of pumps for diesel and gasoline (the latter already disappeared when the electronic injection appeared ). These two types are: the line pumps and rotary pumps.


This injector pump, receives the movement from the engine generally through a drive such as the distribution, so that it rotates synchronized with it, and half revolutions in a 4-stroke engine.

The pressure is regulated by a screw and has no electrical circuit.

Internally it has a piston adjusted with great precision (2 micrometers ) that has two simultaneous movements: rotary to distribute, and axial to compress the diesel.

The diesel oil flow regulation is done by means of an annular slide that opens the pressure piston discharge more or less late, depending on the position of the accelerator pedal and the engine speed at that time. When the discharge is opened, the pressure in the injector falls below the opening pressure of the spring, the injection being terminated.

In the case of in-line pumps, the oldest chronologically, there is a flow piston for each cylinder. The pistons are driven by an internal camshaft of the pump, in the order of starting the engine. In this case, the flow rate is regulated by the simultaneous rotation of the pistons by means of the action of a rack, whereby the pressure discharge channel is discovered sooner or later, dosing the injector as in the rotary pump.

It has the disadvantage with respect to other types of pumps that are heavier, bulky and can not turn at high revolutions, however it is the most used in diesel engines of heavy equipment and cargo trucks whose engines are not very fast, for its robustness, useful life and stability. The graph also shows the tubes that leave the pump to the injectors.

All the pistons feed on a common conduit made in the pump body.