bmw x5 e70 diesel fuel pressure drop

[shurik]

HI everyone. I've got bmw e70 diesel which doesn't start due to fuel pressure drop in a system.

i have changed the fuel filter. had a car connected to the factory scan tool which also indicated fuel pressure drop.

when the engine is cold i can only start it by spraying an aerostat into the inlet. next i have cracked fuel supply pipe nut to the injector and while i am cranking not much pressure coming out of the pipe but as soon as the engine starts with the help of the aerostat the pressure from the pipe nut is absolutely huge. the engine starts and runs and the car drives perfectly fine.

when the engine is warm it is possible to start without using the spray but it takes a long way to crank.

it feels like a fuel pressure regulator is lacking off pressure and it takes time for the pump to build it again.

is a fuel pressure regulator built in the pump or somewhere on a fuel rail? and how i can test it?