My TD6 Wont start.,it will if you give it an Easy Start shot though.
The diaog give a code low rail pressure at start up.
I changed 1 injector 30k ago and the other 5 yesterday hoping that it would cure the issues. Before the injector change the fuel rail had a reading of 82 bar whist cranking after that has risen to 102bar but thats still not enough to start with out the Easy Start boost. When the engine is running the rail pressure meets the demand required at well over 300 bar.
The fuel pumps must be ok for it to run normally when started?
Would it be the O ring on the HPFP ? I have the gasket kit but am not sure where it is or if I would run out of talent attemping to change it. 

Click image to enlarge

All is good now.
5 injectors changed and the O rings in the fuel regulator valve changed also.
It starts the best for years, changes up earlier , is smoother and goes alot faster. Will just wait on the mpg figures for the complete story. 

Click image to enlarge