The best way to find out how an unknown pump control works (when you don't have accsess to technical information) is to "gut" it, study in detail, follow the oil passages and come up with the schematics using your head and prior experience. This procedure can be applied to any unfamiliar component and is called back engineering (or reverse engineering). It is, by far, the best way to learn existing industrial designs and a great mind exercise. Here are some of my own "back-engineerings". Should you bump into a mistake, please let me know - I am doing my best to present the information as accurate as possible, but I am still only human...
Rexroth R978035707 Motion Control Manifold
Danfoss PVEH Electrohydraulic Actuator - What's Inside?
Recovering an Old Parker Flow-Meter, Part One
Recovering an Old Parker Flow-Meter, Part Two
Recovering an Old Parker Flow-Meter, Part Three
Parker SCJN-600-01 Digital Pressure Gauge Design Thoughts
Wika A-10 Pressure Transducers - Did Wika Fail Me?
The Cheapest Digital Pressure Gauge I Could Find
The Analog Front End of the Cheapest Digital Pressure Gauge
Sauer Series 90 Pump
Sauer Series 51 Motor
Liebherr LPVD 064
John Deere Radial Piston Pump
A Very Important Add-on for the John Deere Radial Piston Pump
Komatsu Pump From PC 240
MS control for A4VG Rexroth pumps, used by O&K, Liebherr, and others...
Komatsu D7F50026 pump, simple displacement control - first stop before going into OLSS
Komatsu OLSS Pump, pressure cut-off and torque limiter - the OLSS, finally!!!
Filter holding manifold with cooler connections, an option for Sauer Danfoss series 90
Komatsu Pump From PC 340 - thorough this time!
Uchida AP2D14LV1RS7 Double Pump
HP pump M6PV72-72, with automotive and pressure compensator control
Kawasaki K3V - Transforming Negative Displacement Control into Positive
Linde BMV 105 Variable Displacement Motor