Piston pump with improved guidance

The pump has a movable piston (2), a cylinder element (3), in which the piston is partly led, and a separate second guide (4) with a guidance section (6). The piston is led into, and a filter (5) is integrated into the guide. The piston has a drilled hole (8) and a cross hole flowing into the drilled drilling. Fluid flows in an inlet (21) by the pump through a filter and the cross hole (9) into the drilled hole. The drilled hole has a valve seat and the second guide has a seal for the cylinder element.