Hi... I really don't have any suggestions here. I think you need to have some alternate parts to start out. Make sure the propane and fuel inlets are not mixed up as that would cause you some issues but i doubt you'd reach 75k with the inlets mixed up. Without a known to be good pump, and real working knowledge of the engine you might be chasing your tail.

Try flushing the pump and running fuel through it circulating it for while. if it seems sluggish take it apart. there are only two screws but be careful not to lose the gears the pin or the o-ring in the cover. I would use 5volts to do this. I don't know that I lean toward the pump here but this is all guess work and I am a mechanic so I take known to be good parts and rule things out so you can deduce what is wrong without guesswork

Andy