Well the new IP came in last week and got the hydraulic head installed over the weekend. With both the hydraulic heads pulled out, I went ahead and compared the two. The old one definitely felt "wore out." The plunger easily moved up and down and the red toothed gear spun very easily. The replacement HH I could not move the plunger up and down nearly as easily as the old one. Clearly a tighter fit.
Once put back together, a quick shot of starter fluid, and the truck roared to life! It runs better than when first purchased! So yet another story of a bad hydraulic head. Lesson to be learned: always filter WMO BEFORE putting it in your tank!