I know this post is a bit old, and you may not even come round here anymore...

But I too have been dealing with the same issue (even down to the low pressure readings off the sensor being the same values...)

I've found by unplugging the pressure sensor off the front of the common rail that the indicated pressure value and target value both set to 400bar and the truck fired straight up.

I've been reading around the last few days about people having similar issues and going down the injector leak down testing route to establish leaky injectors too....

I've noticed on mine, if i let the truck sit for a while and then start it, it's quite heavy on diesel fumes and gasses out the back, so the leaky injector path is my next place to start looking.

I'm not sure how that would play into the fact of the low pressure on crank apart from them leaking that badly they don't allow pressure to build up at all...

I may have two separate issues at play here, one being leaky injectors leading to the smoke on start-up
And two being the pressure sensor off the rail being faulty.

Just thought I'd give you some information from my own experiences of dealing with this same issue...