Abstract: An injection system for an internal combustion engine, in particular an engine operating on liquid gas as fuel or fuel component, includes an injection unit for each cylinder for direct fuel injection into the combustion chamber, and a fuel supply system with at least one fuel tank and an oscillating pump element configured as a displacer for delivery of the fuel. The pump element is provided with an elastic sealing element fitted in a housing and which divides a pump chamber into two subchambers sealed tightly against each other, the first subchamber being supplied with fuel via a fuel feed line of the fuel supply system, and the second subchamber being supplied with a secondary medium. The dead volumes of the pump element may be reduced by configuring the pump chamber as an annular chamber at least partially surrounding a shaft moving axially in a cylinder, which shaft is mechanically linked with the sealing element.