So, why are so many of these Ford PMGR solenoids failing at such low hours? Skylor had an interesting theory: on airplanes, the ring gear and starter nosecone are exposed and pull in dust and grit kicked up by the prop and deposit that dust on the plunger of the solenoid, which eventually binds it up. To be clear, I'm talking about the smaller metallic cylinder, not the white plastic part. The clearance is pretty tight on that plunger. Of the three I've had fail in 750 hours, all have had sticky plungers. Cars have their ring gear and starter nose enclosed with a dust shield.
Or, the problem is cheap offshore-sourced parts. Including the ones that Sky-Tec supplies.
As shown below, the solenoids we're using look like this:
There are ones available which have rubber dust caps on the plunger; need to check if they will fit in the Sky-Tec housing. If so, could be an improvement.