Abstract: A high pressure fuel pump unit and assembly is provided which includes a pump barrel containing a bore, a pump plunger mounted in the bore for reciprocal movement between an advanced position and a retracted position, and a force transmitting device for transmitting axial loads to the plunger while minimizing side loads on the plunger. The force transmitting device includes an extension member extending into the inner radial extent of a bias spring and including a distal supporting end positioned in uncoupled abutment against a driven end of the pump plunger to form a decoupled force transmitting interface. The pump plunger and extension member are capable of relative lateral movement at the decoupled force transmitting interface which is positioned a spaced axial distance from the outer end of the pump barrel when the pump plunger is in the advanced position.