Method of pumping fluid from a wellbore by a subsurface pump having an interior flow passage in communication with a fluid chamber via a filter positioned in a side wall of a plunger

A pump can include a plunger and a barrel, at one stroke extent flow being substantially restricted between the plunger and the barrel at spaced apart positions and a plunger interior passage in filtered communication with a fluid chamber between the positions, and at an opposite stroke extent the fluid chamber being in communication with the standing valve. A method can include displacing a plunger in one direction, thereby receiving filtered liquid into a fluid chamber, and b) displacing the plunger in an opposite direction, thereby transferring the liquid to a barrel interior passage. A system can include an actuator that reciprocates a rod string, and a pump including a plunger with a traveling valve, a barrel with a standing valve, and a filter that filters liquid which flows from a tubing string to a compression chamber disposed between the traveling valve and the standing valve.