Hello! I also have after a problem with the car, which I replaced the high pressure pump that chipped. I bought a new pump, took the injectors to a repair shop, cleaned the entire fuel system and tank, every line apart. I primed the pump well before the first key.

After I installed new parts, the car drove without problems for about 100 km, after which it gave P0087 again, too low pressure in the rail, an intermittent, sporadic problem. The pressures at the time of the error are apparently OK (see in the code at the end, where it gave too low pressure at 1.118 bar...). After turning the engine off and on, the limitation and warning light would disappear.

Besides that, in two mornings, in the cold, it gave too much pressure, the following days it didn't have any more issues).

I replaced the rail pressure sensor and the rail pressure regulator, to no good, same behavior. I reset the values ​​learned from all sensors, rewrote the injectors (although they were the same, put in the same positions), to no good. I even tried putting the old pump pressure regulator on after cleaning it as best I could with brake spray and compressed air.

I also have an A4 2.7 that had a pump failure last year that had a similar behavior, but there it was losing fuel on the return of an injector. Here everything is clean, it doesn't lose a gram of diesel anywhere, I even changed the injector caps.

In fact, neither I nor my colleague with whom I did the work know what to do anymore. Maybe someone has encountered a similar problem and can give me an idea.

Code:
Tuesday,17,January,2023,18:32:09:00007
VCDS Version: Release 18.9.0 (x64) Running on Windows 10 x64
www.Ross-Tech.com

Address 01: Engine Labels: 059-907-401-V1.clb
Control Module Part Number: 8R0 907 401 J HW: 8K1 907 401 A
Component and/or Version: 3.0TDI EDC17 H14 0008
Software Coding: 0114002C240F0928
Work Shop Code: WSC 36765 142 97888
ASAM Dataset: EV_ECM30TDI0118R0907401J 001008 (AU48)
ROD: EV_ECM30TDI0118R0907401J.rod
VCID: 39799BE5B8599582D2-806C
1 Fault Found:

5211 - Fuel Rail/System Pressure
P0087 00 [167] - Too Low
MIL ON - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 244419 km
Date: 2023.01.17
Time: 18:05:12

Engine speed: 2195.00 /min
Normed load value: 96.5 %
Vehicle speed: 116 km/h
Coolant temperature: 87 °C
Intake air temperature: 28 °C
Ambient air pressure: 990 mbar
Voltage terminal 30: 14.240 V
Unlearning counter according OBD: 80
Crankshaft speed (RPM): 2195.0 /min
Vehicle speed: 115.46 km/h
Mean injection quantity: 58.88 mg/stroke
Fuel temperature: 40.4 °C
Fuel high pressure: actual: 1.1189e+006 hPa
Rail pressure regulation: status-Bits 0-7: 00000101
Inj Crv st Inj Char Act Val 0-Bits 0-7: 00010100


Readiness: N/A