I think it is called trouble shooting, start with what works and see where it brakes.
you could also ask scthom about it.
As a off note, and Not that this has anything to do with you, but it was on my mind and is sort of related (just a story about a event in history).
Today a tech was wondering why his PDS (Parameter distribution system) sprayer (for pest control) would not spray chemical. Looking at his system I Immediately noticed there was no gasket in the filter (the filter housing is see through), and two hose connections were lose. Instead of thinking things through and possibly fixing it. the tech wanted to argue with me (for 30 Min's or so) waisting more of his time he said he did not have to "Fool With It". Once he did what I said it all worked just peachy and only took about 1 min to fix.
I shook my head as he rode off in the sunset.