Fuel injection system for an internal combustion engine

Claim 1

A fuel injection system for an internal combustion engine with solenoid-valve controlled fuel injection nozzles receiving fuel from a common high pressure fuel supply line, said fuel injection system comprising a mechanically operated high-pressure pump connected to said common high pressure fuel supply line by way of a high-pressure line including a check valve for supplying fuel under pressure to said common high pressure fuel supply line, said high-pressure pump having a pump piston disposed in a cylinder and defining therewith a pump working space, a low-pressure fuel feed line in communication with said pump working space for feeding fuel thereto when said pump piston is in a retracted position, a control line extending between said high-pressure line upstream of said check valve and said fuel supply line and including a solenoid valve to permit the discharge of fuel from said pump back to said fuel supply line when the pressure in said common high-pressure fuel supply line is sufficient, and a bypass line providing communication between said high-pressure line downstream of said check valve and said fuel supply line via flow passages formed in said piston and through said piston working space when the piston is in an inserted position and said solenoid valve is open to permit the release of pressurized fuel from said common high-pressure fuel supply line to said fuel supply line.