A fuel system includes a low-pressure fuel delivery unit; a high-pressure fuel delivery unit which has a drive region and a delivery region such that the drive region supplies fuel to the delivery region and such that the delivery region supplies fuel to a high-pressure fuel injector; a low-pressure fuel supply passage which supplies fuel from the low-pressure fuel delivery unit to the drive region of the high-pressure fuel delivery unit; a cooling passage which receives fuel from the drive region of the high-pressure fuel delivery unit; and a low-pressure fuel injector supply passage which is in direct fluid communication with the low-pressure fuel supply passage and which supplies fuel to a low-pressure fuel injector from the cooling passage.

A plug-in pump for a common-rail system has a pump housing having a cylinder formed therein and a piston guided in the cylinder, a fuel inlet, and a fuel outlet. The pump housing also includes a plug-in section for inserting the pump housing into an opening of an engine component, and a flange that delimits the plug-in section, for fastening the pump housing to the engine component. To cool the plug-in pump, the pump housing has at least one flow duct with a separate fluid inlet and a separate fluid outlet. The fluid inlet is connectable to a fluid-discharging line of the internal combustion engine, and the fluid outlet is connectable to a fluid-receiving line of the internal combustion engine.

A fuel pump includes a first plunger that reciprocates in a first cylinder. The fuel pump further includes a first mover connected to the first plunger; a second mover that serves as a counterweight for suppressing vibration that occurs due to reciprocating movement of the first mover; an electromagnet and a magnetic member that are provided between the first mover and the second mover; a plate disposed between the first mover and the second mover; and a third spring and a fourth spring being a pair of springs sandwiching the plate between the third spring and the fourth spring, the third spring and the fourth spring having end portions connected to a housing.

A fuel pump according to the present invention includes: a pump head; a plurality of plunger barrel units that are mounted in parallel with the pump head and that include a plurality of pressurization chambers in which a plurality of plungers are movably supported, and in which fuel is pressurized by movement of the plungers; a plurality of discharge valve units disposed in a plurality of fuel discharge channels provided to the pump head so as to each communicate with the plurality of pressurization chambers; a plurality of suction valve units disposed in a plurality of fuel suction channels provided to the pump head so as to each communicate with the plurality of pressurization chambers; a fuel discharge side communication channel by which the plurality of fuel discharge channels are communicated; and a connector that is capable of externally supplying fuel in the fuel discharge side communication channel.

A desmodromic mechanism exhibits reciprocating motion of a pair of cam followers driven by a single cam. The mechanism is useful in a fuel pump that pressurizes a liquid for delivery to a fuel rail of a combustion engine. A desmodromic lever is symmetric about its rotational axis and maintains continuous contact between cam lobes and cam followers for the entirety of each rotational cycle. The mechanism is particularly useful in multi-piston pumps required to deliver higher than normal volumes of liquid fuel, as is the case with low energy density alternatives to diesel fuel.