Excavator Hydraulic Pump 708-3S-00961 708-3S-01850 Komatsu PC50 PC55 PC56-7 Main Piston Pump Komatsu PC56-7 Hydraulic Pump Common Faults The main pump for Komatsu PC56-7, part No. 708-3S-00961, is a variable displacement piston pump integrated with a tandem pilot gear pump, equipped with PC-EPC electronic flow control solenoid valve. Primary failure causes include contaminated hydraulic fluid, suction-side air ingress, defective PC-EPC solenoid valve, and seized regulator