Not familiar enough with this type engine. Just a few other thoughs though and not meant to frustrate you as you may have covered already. I would warm up and shut down. Remove return line from injection pump and see if any fuel discharge when cranking hot. Just primarily verifys lift pump is not going down when engine hot I think. If your problem was quitting on road only would suspect back pressure (blowby) shutting down pump with perhaps semi obstructed bypass system as a possibility. I do not think engine can retain blowby pressure after shutoff when warm but you may want to verify again because it is so easy to do. Simple as removing oil fill cap prior to trying hot restart..