[bestgenman]

I've been following this conversation and don't have much experience with older Newell's with Perkins powered sets.  My input is to operate the switch (your helper operates the switch) and listen or feel the pump to see if it operates.

 All injection pumps need a positive pressure at the inlet provided by a mechanical or electric pump.  The most common problem with hard starting is no fuel at the injection pump likely caused by filters.  Lines on the suction side of the pump, even though they look good can leak air into the fuel system, not good!  Your lift pump, either mechanical or electric should be operating when the engine is running.  It is entirely likely the switch, as Dean states, is momentary for priming.  You'll know once you determine what the "mystery switch" does.  You state the switch is maintained rather than momentary, is that a correct assessment?  I can't imagine the running instructions require the pump switch to be turned on every time you start the engine, but I have been fooled many times before!! 

Otherwise, this engine should run if positive pressure is on the inlet of the injection pump unless there are stuck components in the injection pump.  This is highly unlikely.  

Let me know what you find.