Well it's official, I killed the HH by starving it!
I installed the HH at lunch today. Bleed the system and bumped the starter, it roared to life. Not even any starting fluid.
I'm not upset, it was a $150 mistake. (Thank you again Tony!) I was trying to be cheap, and it ended up costing me more instead of stopping at the gas station on the way to my friends shop. It lurched at the traffic light at the gas station's corner, I should have filled up then. But I thought ehh I've only got 3 miles till I get "free" fuel. I can make it that far.
I really don't think the WMO played a factor in this failure. Me keeping my foot in it with it saying no more for a 1/4 of a mile downhill with nothing lubing the HH is what did it in. When the wife gets home tonight (I dunno where the camera is from last weekend's trip) I'll take pics of the plunger to show the issue.
I'm simply happy at this point in time that it's running again!
Lesson: NEVER starve a HH for fuel. If it bogs down for a lack of fuel, put it neutral and let the engine shut off. Let it coast to a safe point, then check the fuel system.
Also, I'm considering adding a tee on the bleeder port of the secondary filters. And installing the oil pressure pump I have perm. I can safely know then any fuel related pressure issues to the HH in the future. I've got to buy some fittings to "dual line" my 931 anyhow. Cheap insurance and yet another gauge I can use to monitor what's really going on.