Rail pressure too low

[TrashCo]

Hello everyone,

I've been driving a 120D E87 with the N47 177HP engine for several years.
The good one has always run perfectly so far, only sees long distances every day and now has 310,000km on the clock.

Unfortunately I've been having problems with rail pressure for 2 weeks. According to INPA it throws me the following errors:

- 004560 Rail pressure plausibility quantity controlled
- 004570 Rail pressure plausibility quantity controlled
- 004610 Rail pressure plausibility pressure-controlled


The first time this happened was on the motorway at 130kmh, it went into emergency mode but was able to continue driving, 500m before my garage entrance at 50kmh the engine turns off and wouldn't start. My wife then towed me away and 15 minutes later he came back in the garage at home, but very difficult.
Now it always starts after about 6-10 revolutions, in idling the engine is very quietly running and you can also drive at partial load without any problems. At full throttle boost pressure come in and it accelerates properly (as I know it from him), but then after about 1 second it runs in emergency mode, you can continue driving with not to much throttle, but if you continue full throttle the engine turns off and won't start again - wait 15 minutes then it comes back again very difficulty... What I've done so far is replace the diesel filter, according to INPA the delivery pressure of the tank pump delivers 7 bar which is sufficient. The rail pressure is at 87bar during the starting process after a failure. After waiting 15 minutes it is at 330 bar which means it starts badly but starts. While driving in the partial load range, the setpoint is 900bar and the actual value is 870bar. When accelerating, it reaches a maximum of 1400bar and then switches to emergency mode.

My question: could this be due to the HP pump or is the pressure control valve or flow control valve causing problems? I'm thinking about whether it could be that the pressure control valve is defective or leaking and I'm losing rail pressure via this valve. also i've read in forums that a defective flow control valve is supposed to not be noticeable or cause any problems.

A defective HP pump would not be able to reach 1400 bar or am I mistaken?

Thanks & greetings
TrashCo