Abstract: A positive-displacement pump (lifting pump) comprises a pump housing with a pump chamber having an inlet and an outlet passage controlled by an outlet check valve; a displacement member which delimits the pump chamber in one direction of movement of the displacement member and which is reciprocable in the pump chamber within a stroke region and includes a second check valve opening into the pump chamber within a stroke region and includes a second check valve opening into the pump chamber and disposed in a passage between the inlet and the pump chamber; and an actuating mechanism for repetitively reciprocating the displacement member in the pump housing within the stoke region.