Ok, I'm still trying to figure out why this one won't start. So far:

Glow plugs check out resistance wise and are getting power
New fuel filters
Fuel flow from main filter
K40 fully functioning
Audible click at SOV (new less than 1 year ago)

I just removed the SOV, and connected a hose to the outlet to the pump. When you turn the ignition on the SOV opens momentarily, then immediately recloses. This is also reflected in the fact that the engine fires a couple of times when you first try, then stops firing. It never fires enough to consider it running.

Previous owner still has slightly leaky SOV he took off less than a year ago, so I'll have that to try tomorrow. To me it seems like it could be the valve, or the signal to the valve. Is there some logic applied that the engine has to be spinning (read from crank signal back by starter) to keep the valve open? Any other thoughts?

Recent history: car ran fine and was daily driver until small front end impact about 3 months ago. Sat unstarted for 2 months, then started immediately and ran fine to pull onto trailer. Started a couple more times moving it around, then gradually ran worse until it wouldn't even start.