A fuel pump for an internal combustion engine is provided comprising a barrel including a central bore having a longitudinal axis, a plunger disposed partially in the central bore and movable along the longitudinal axis, a spring retainer, a first coil spring having a proximal end in contact with a first section of the barrel and a distal end in contact with the spring retainer to urge the spring retainer into engagement with a tappet assembly, an extender element coupled to the plunger, and a second coil spring having a proximal end in contact with a second section of the barrel and a distal end in contact with the extender element to urge the plunger toward the spring retainer, wherein the extender element includes a counter-bore to couple the extender element to the plunger.

A fluid end of a pump includes a body that defines a suction bore, a discharge bore, and a plunger bore. A first central longitudinal axis extends through the suction bore, the discharge bore, or both. A second central longitudinal axis extends through the plunger bore. A chamber is defined at an intersection between the suction bore, the discharge bore, and the plunger bore. An interior surface of the body that at least partially defines the chamber comprises a first wall portion that is at least partially planar and oriented at an angle that is less than or equal to 15 from perpendicular to the first central longitudinal axis.

A connecting rod for an air compressor includes a rod member, a wrist pin receiving end connected to a first end of the rod member, and a crank pin receiving end connected to a second opposing end of the rod member. A separation line for the connecting rod is provided above the crank pin receiving end. The separation line may be provided between the crank pin receiving end and the rod member. The connecting rod may include a first portion including the rod member and the wrist pin receiving end, and a separate second portion including the crank pin receiving end. The separation line may be provided between the first portion and the second portion.

A hydraulic pump assembly including a first pump, a second pump, a shaft, and fluid lines is disclosed. The first pump includes a first piston assembly. The second pump including a second piston assembly. Each piston assembly of the first and second pumps includes a cylinder and a piston slidably disposed in the cylinder. The shaft connects the first pump to the second pump and is configured to displace the pistons within the cylinders of the first and second piston assemblies. The fluid lines fluidly couple the first piston assembly with the second piston assembly to form paired piston assemblies. The first piston assembly is phase shifted from the second piston assembly.

A planetary drive system that aligns four fluid ends for a pump or four compressor cylinders in the same plane, allowing for four fluid ends/compressor cylinders to be driven by one rotation of the pump's motor. Additionally, the planetary drive system is stackable to allow, for example eight, twelve, or other multiples of fluid ends or compressor cylinders to be driven while minimizing any reduction in output pressure. The chemical injection pump also includes threaded vents on the fluid ends to capture chemicals primed through the valves to avoid spillage and waste during the priming process. The air compressor cylinders also include pistons with enhanced vacuum actuation under a flexible inlet (e.g. flapper inlet).