[bestgenman]

You’ve given a fair amount of information here and my bet initially is a filter restriction. “Slowed and stalled” supports no fuel.  If you have fuel pressure of 5psi (don’t know exactly where you gauge is mounted) , there should be enough fuel to the injection pump.  If the gauge is at the output of the primary and the fuel passes through the secondary, you might change that filter.  This is where a picture is worth a lot.

I’m not sure at what level the pickup runs of of fuel but since you filled there is a good possibility of filter clogging material in the generator suction that passed beyond your primary.   And, if the fuel quality is low (dirty or alge laden) it may take a couple of filter changes.

Since it stopped while carrying a fair load, it doesn’t make sense that it is an electrical problem unless it stopped on high temperature and 784 should have a controller indicating the shutdown cause.  If it starved for fuel then it would stop and no oil pressure would be your indication.  Again here, what did the controller report?

The lift pump may be failing also.  It shows pressure while you are attending but during a run it may be loosing pressure (again, a no fuel problem).  If you’re sure the fuel is good and I’m assuming the main engine is happy with the last fuel load, then swap the pump.  Any 12V 5psi pump will work.  My 5psi rated pump only shows 3psi but works fine.  

These kind of problems are very difficult to diagnose remotely.  I hope this helps.