The owners of N53/N54 (and early N55) series engines know that the high-pressure pumps (HPFP), nevertheless their heavy construction (3 plungers, a massive body, pressure regulation valve of an impressive size, chain drive), tend to fail. The reason usually is trivial – fuel leakage in one of many valves. One of the typically most leaking valves – is the pressure regulation valve. Unfortunately, this valve is not sold separately by the manufacturer. When the defect appears, a new pump should be purchased; there are no other options.
A new pump costs at least EUR 1000; if you return your damaged pump as part of the exchange program.

Code of the pump: 13517616170

When checking the offer on the Internet, some alternatives are offered:
a. pumps, manufactured in Hongkong, with delivery from UK or DE, their price around EUR 300;
b. pumps, manufactured in China with delivery from China, their price is around EUR 150.

Most probably, both pumps are the product of the same manufacturer, only delivery costs to the EU included (which is understandable – time, tax, shipping costs – no one has canceled this).

This time – the experience of one user. Here is the DME error message list after 2 months after installation of such pump:

As we see, the Rail pressure regularly has dropped very low: even till 30 .. 50 Bar (instead of the necessary 200 Bar). At the same time, fuel consumption, measured by the DME, was tiny: only around 2 l/h). The vehicle’s owner used the Rail pressure sensor replacement as the last hope. Unfortunately (as suspected), it did not give any results.

Here how the live data look:

As we see, DME has completely turned off the HPFP, and the engine runs from fuel (and pressure), which is supplied by the low-pressure pump located in the fuel tank.
The abilities of HPFP are so much reduced that several seconds after starting the engine, the Rail pressure drops 4 .. 6 times, and then DME turns off the HPFP completely.
This time we have to conclude that the pumps manufactured by the People’s Republic of China are usable only as scrap metal.