Vehicle booked in for rocker cover gasket oil leak repair. After repairs the vehicle cranks but will not start.

Following rocker cover gasket work, the common rail diesel system was disturbed and the engine developed a crank no start. Engine would start only in fail-safe modes when key sensors were unplugged, indicating the ECU was substituting fixed values to allow limited running. Root cause was injectors mechanically seized from carbon/soot contamination pushed back into the injector internals during an incorrect bleed and restart process after cracking injector lines.