An airless dispenser pump assembly includes a pump mechanism with an inlet valve that is configured to efficiently pump viscous fluids and that is able to be pre-primed when the pump mechanism is attached to a container. In one form, the inlet valve includes a seal member that seals an inlet port of the pump and an outer support member that secures the inlet valve to the rest of the pump mechanism. Two or more legs generally extend in a circumferential direction between the support member and the seal member in order to create a large flow opening for fluid flow through the inlet valve when opened and to rapidly close the inlet valve. The pump mechanism further includes an outlet valve that is configured to draw fluid back from a nozzle of the pump after dispensing in order to minimize build up around the nozzle.