A hydraulic control unit comprising: an HCU block defining an eccentric chamber containing a rotating eccentric ; a piston guide including a first tubular portion extending along a pump axis with a first inner surface having a cylindrical shape receiving a piston rod and allowing said piston rod to translate freely only in an axial direction, said first tubular portion having a first outer surface with a generally cylindrical shape with a return spring disposed thereabout, said piston guide including a base surface extending annularly and radially outwardly from said first inner surface and facing away from said eccentric chamber , with a second tubular portion extending axially from said base surface opposite said first tubular portion and including a second inner surface having a cylindrical shape and radially spaced apart from said piston rod to define a first throat therebetween; and a gland seal disposed in said first throat of said piston guide surrounding said piston rod to prevent leakage thereabout as said piston rod moves axially therethrough, wherein said piston rod has a generally cylindrical shape extending along said pump axis between a first end and a second end , said piston rod having a smooth exterior surface extending substantially the entire length between said first end and said second end , characterized in that the hydraulic control unit further comprises: an end cap disposed around said first end of said piston rod adjacent said rotating eccentric and fixed to move axially with said piston rod , and wherein said end cap includes a flange portion extending annularly outwardly from said piston rod for engaging said return spring . an HCU block defining an eccentric chamber containing a rotating eccentric ; a piston guide including a first tubular portion extending along a pump axis with a first inner surface having a cylindrical shape receiving a piston rod and allowing said piston rod to translate freely only in an axial direction, said first tubular portion having a first outer surface with a generally cylindrical shape with a return spring disposed thereabout, said piston guide including a base surface extending annularly and radially outwardly from said first inner surface and facing away from said eccentric chamber , with a second tubular portion extending axially from said base surface opposite said first tubular portion and including a second inner surface having a cylindrical shape and radially spaced apart from said piston rod to define a first throat therebetween; and a gland seal disposed in said first throat of said piston guide surrounding said piston rod to prevent leakage thereabout as said piston rod moves axially therethrough, wherein said piston rod has a generally cylindrical shape extending along said pump axis between a first end and a second end , said piston rod having a smooth exterior surface extending substantially the entire length between said first end and said second end , characterized in that the hydraulic control unit further comprises: an end cap disposed around said first end of said piston rod adjacent said rotating eccentric and fixed to move axially with said piston rod , and wherein said end cap includes a flange portion extending annularly outwardly from said piston rod for engaging said return spring . <EOS>