James, good post.

With a common rail system I find it is essential to confirm fuel quality and supply before doing any sort of testing, especially if pressure faults are being generated, new fuel filter if there is any doubt as to when it was last changed and a good look and sniff test of the fuel being supplied to the pump, I spent many hours in the past chasing faults only to find the filter was restricting supply.

Vapor in the leak off bottles, worth taking a small sample of fuel and trying to light it?

Cheers
Steve

PS Just saw Tonys post above, all good points