I have a starting D5 again.
The inlet hose to the HP pump was secured using a new hose clamp but not before:
- Brimming the inlet line with diesel via a vacuum pump,
- Blocking off the HP pump inlet and drawing vacuum at return line to test for leaks, and finally,
- Pulling a vacuum via the return line to force diesel from the (brimmed) inlet line to the HP pump.
I thought I had the system sufficiently primed to have a firing engine from a single turn of the key, but it took 10, see below:
I let it idle for around 10 minutes while double-checking for any leaks, followed by some revving. I also stopped and restarted the engine a few times.
I'm still convincing myself to take it out, will report back later.
Here's hoping that the non-starting issue was leak-related and nothing else and that my HP pump is still serviceable.
Thank you, everyone, for your help.