A high-pressure pump includes a pump cover, an air cylinder, a piston, a water cooling device, and a pump seat. The air cylinder is formed by a first air cylinder, a second air cylinder and a third air cylinder whose diameters are progressively reduced and that are coaxially disposed. The piston is also formed by a first piston, a second piston and a third piston whose diameters are progressively reduced and that are respectively disposed in the first air cylinder, the second air cylinder and the third air cylinder. A water cooling device is disposed between the second air cylinder and the third air cylinder.

A high-pressure pump includes a pump cover, an air cylinder, a piston, a water cooling device, and a pump seat. The air cylinder is formed by a first air cylinder, a second air cylinder and a third air cylinder whose diameters are progressively reduced and that are coaxially disposed. The piston is also formed by a first piston, a second piston and a third piston whose diameters are progressively reduced and that are respectively disposed in the first air cylinder, the second air cylinder and the third air cylinder. A water cooling device is disposed between the second air cylinder and the third air cylinder.

In order to prevent working medium from accumulating in the compressor housing (2) of a piston compressor (1) in a simple manner by means of a sealing of the piston rod (7) in the form of sealing medium barrier supplied by a hydraulic unit (12), it is provided that a ventilator (32) and a sealing medium container (37), which is partially filled with sealing medium, are provided in the hydraulic unit (12), wherein the ventilator (32) suctions air from the free space of the sealing medium container (37), and the free space (45) in the sealing medium container (37) is connected via a line (15, 17) to the compressor housing (2), and an opening (16) is provided at the compressor housing (2) for connecting the interior of the compressor housing (2) to a purge gas reservoir (18).

In order to prevent working medium from accumulating in the compressor housing (2) of a piston compressor (1) in a simple manner by means of a sealing of the piston rod (7) in the form of sealing medium barrier supplied by a hydraulic unit (12), it is provided that a ventilator (32) and a sealing medium container (37), which is partially filled with sealing medium, are provided in the hydraulic unit (12), wherein the ventilator (32) suctions air from the free space of the sealing medium container (37), and the free space (45) in the sealing medium container (37) is connected via a line (15, 17) to the compressor housing (2), and an opening (16) is provided at the compressor housing (2) for connecting the interior of the compressor housing (2) to a purge gas reservoir (18).

Provided is a configuration which prevents an engine from being unable to start in the state in which dew condensation occurred in a fuel injection pump and froze. The present invention relates to a fuel injection pump which is provided with a pump body and a hydraulic head and driven by an engine, and is characterized in that while the engine is in operation, the temperature of the hydraulic head is increased to a dew-point temperature or higher. Consequently, it is possible to increase the temperature of the hydraulic head and remove water in the fuel injection pump while the engine is in operation. Accordingly, the engine can be prevented from being unable to start in the state that dew condensation occurred in the fuel injection pump and froze.

Provided is a configuration which prevents an engine from being unable to start in the state in which dew condensation occurred in a fuel injection pump and froze. The present invention relates to a fuel injection pump which is provided with a pump body and a hydraulic head and driven by an engine, and is characterized in that while the engine is in operation, the temperature of the hydraulic head is increased to a dew-point temperature or higher. Consequently, it is possible to increase the temperature of the hydraulic head and remove water in the fuel injection pump while the engine is in operation. Accordingly, the engine can be prevented from being unable to start in the state that dew condensation occurred in the fuel injection pump and froze.

A water pump drain plug has a first end which is adapted for engagement to a water pump drain opening which communicates with the pressurized fluid within the water pump. The drain plug has an axial passage communicating therethrough capable of draining fluid from the water pump. The axial passage is plugged initially by a sealing member engaged therein which will release upon communication of fluid pressure against it at a predetermined release pressure.

A water pump drain plug has a first end which is adapted for engagement to a water pump drain opening which communicates with the pressurized fluid within the water pump. The drain plug has an axial passage communicating therethrough capable of draining fluid from the water pump. The axial passage is plugged initially by a sealing member engaged therein which will release upon communication of fluid pressure against it at a predetermined release pressure.

A piston pump as a high-pressure fuel pump of a common rail system includes: a pump cylinder; a pump piston moveably mounted in a recess of the pump cylinder, the pump piston being moveable up and down in the recess; and a leakage groove arranged in the pump cylinder in a region of the recess, the leakage groove being coupled with a leakage line configured to discharge a fuel leakage. Between the pump cylinder and the pump piston a different size pairing clearance is formed in first and second portions of the pump cylinder.

A piston pump as a high-pressure fuel pump of a common rail system includes: a pump cylinder; a pump piston moveably mounted in a recess of the pump cylinder, the pump piston being moveable up and down in the recess; and a leakage groove arranged in the pump cylinder in a region of the recess, the leakage groove being coupled with a leakage line configured to discharge a fuel leakage. Between the pump cylinder and the pump piston a different size pairing clearance is formed in first and second portions of the pump cylinder.