Mercedes X Klasse Diesel Engine Stalling Issue

A faulty fuel volume regulator can cause those symptoms. Engine misfire, stalling, and reduced power are common. It can also affect fuel efficiency if the fuel injection isn't working correctly. The car sensors are reporting the fault, so that's a good starting point. What were the exact error codes?

The error code that came up was P0093 - Fuel System Leak Detected - Large Leak. Does this error code confirm the fuel volume regulator, or could it be something else entirely? I'm trying to gauge how urgent this automotive repair is. Is driving with this issue potentially damaging to the engine?

That code can relate to a fuel volume regulator issue, especially with the symptoms you describe. While it could theoretically be other things in the fuel system, the regulator is a likely culprit given the circumstances. It's hard to say definitively without further testing. I would recommend taking it to a workshop to have the fuel pressure tested and the regulator inspected. Driving with a fuel system issue can damage the engine in the long run, so I would advise against prolonged use.

I took it to a local shop, and they confirmed it was indeed the fuel volume regulator. Turns out the high pressure pump was defective, just as suspected. The whole repair, including parts and labor, cost me 1510€. Hopefully, this fixes the problem for good!