Fuel injection pumps are a technical marvel of their time. I'm not a pump rebuilder but I think I have a basic understanding of how they work. You appear to be a pump rebuilder so I would expect that you would have a greater knowledge of the various systems and components of said pumps than I do. Everyone here understands this, as do I. Since I have no intention of ever becoming an IP rebuilder, I'll leave that up to the experts.
However, in order to correctly diagnose a defective IP, one needs to know enough about how they work in order to
not send a perfectly working pump off to be rebuilt. In the event that the said pump gets rebuilt, and the engine
still runs terribly afterwards, I've just spent the customers money and perhaps a large part of their budget as well. I have a number of tests and adjustments I make before I send a pump off to be rebuilt, so a fairly high understanding of
all of the working components of the engine ( which includes the IP ) becomes key to any sort of success.
I often tell customers that they probably don't need to know how to rebuild an engine; they need to know how to properly maintain one after its been rebuilt. The same goes for injection pumps - I need to know if one
isn't working, not how to rebuild it. Send me a PM with your phone number if you like.