Get the manual for the I2/3 valve and then the maxton etc. Go through and read the sections on the order of events of how the oil flows and is controlled by the solenoids opening/closing and the sequence that follows. I say start with the I2/3 because they have very good explanations of this and pictures, you will be able to fully understand how the oil is controlled and how it moves the pistons etc. There's not much better way than this other than someone hands on teaching you with the diagrams/a real valve to disassemble. Say look at the oil line input to the jack, how's the valve stopping oil flow at rest? How's it changing that to allow the car to move? What's happening when the car runs up?

If you need manuals PM me

Honestly I'm not sure I've ever seen a book book on what your asking. All of my experience/knowledge came from installing alot of hydros and also alot of service calls on them. Sometimes there no answer other than trying things till you figure out the problem of the day

Alot of times isolating/narrowing down the issue area is done by careful consideration of all symptoms and logically ruling things out to methodically narrow down the direction your looking in. Setting up tests or adjusting something to determine if it got worse or better or no affect at all, might tell you your in the ballpark or look at something else entirely

Thanks for the advice. I have an I2/I3 manual in my files, I’ll read it with what you said in mind.

youtube.com/lindenelevator

Roy made some videos of maxton/eeco/dover valves that are very helpful. Other then that its all about experence