A rod actuated downhole well pumping system is provided with spaced apart annular elastomer members secured to the pump rod at predetermined intervals to prevent solids particulates entrained in the pumped fluid from settling down to and clogging the pump mechanism during periods of pumping activity. The elastomer members are provided with longitudinal slits so that they may be sleeved over a pump rod without disconnecting the rod from the pump assembly in retrofitted installations. The elastomer members are preferably secured to the pump rod with a suitable adhesive and are of a diameter at least slightly less than the inner diameter of the tubing through which fluid is being pumped.