[v8volvo]

Diesels don't take much to run. All you need is fuel, heat, timing, and compression. Ruling them out one by one: you say you have at least 5 good plugs and they are getting power. Should be enough to get it started, so there is your heat. Compression, it might not be perfect but you surely have some since compression doesn't disappear overnight unless you overheat or do something else dumb. Fuel, you probably have enough if you are seeing smoke (though you should check by loosening the fuel union nuts at the injectors and cranking the engine on a fully-charged battery with accelerator to the floor -- fuel should come spurting out all 6 lines).

That leaves you with timing, the most likely thing to change suddenly other than glow plugs and cause a starting issue. When was the last time the front and rear timing belts were changed? How tight are/were they? Any teeth missing from either one? Skipped timing will make the engine impossible to start. I'm guessing that is where your issue is.