FIG. 1 is a perspective view of a first embodiment of a paint spray pump housing; FIG. 2 is a front view thereof; FIG. 3 is a right side view thereof. FIG. 4 is a left side view thereof. FIG. 5 is a bottom view thereof; FIG. 6 is a top view thereof; and, FIG. 7 is a back view thereof. The details shown in broken lines form no part of the claimed design.