A reciprocating pump assembly comprises: a motor with a rotary motor drive shaft; a cam coupled to the motor drive shaft with an axis of rotation and a cam channel cut generally axially into a radial face of the cam; and multiple reciprocating pump units arranged radially about the cam axis of rotation, each with an inlet valve, an outlet valve, a plunger and a plunger sleeve, with a free end of its plunger coupled to the cam by way of a cam follower riding in the cam channel; wherein rotation of the motor output drive shaft causes the plunger in each pump unit to independently reciprocate in its respective sleeve.