[PDF] Basic Trouble Shooting Motor/Solenoid Equalizer Hydraulic Basic Trouble Shooting Motor & Solenoid for Equalizer Hydraulic Pumps Uni-Directional Pumps 12 VDC Equalizer Pump Numbers 2015, 2017, 1551, 1531, 2016, 2142, 1636 These uni-directional (motor only runs one direction) units can be identified as having one motor solenoid. SPX Stone Fenner Fluid Power Unit Parts - Page 1 - Melrose 1118AA SPX Stone Hydraulics Pump Coupling $16. 1118-AA SPX Fenner Stone Hydraulics 9 Spline Coupling. 1" long with center stop. This coupling is located between the pump and the motor on SPX Fenner Stone hydraulic power units. 11/16" O.D., 1/2" I.D. (slot to slot)..