Product Overview This hydraulic main piston pump is the core power component of the excavator hydraulic system, compatible with the E312D2 and 313D models. It supplies pressure oil for boom, arm, bucket, and travel movements. Manufactured with precise processing, it delivers stable output pressure and excellent wear resistance, making it an ideal choice for machine overhaul and replacement. Part Number 391-9442 Component Type Hydraulic Main Piston Pump Compatible Models