@advmom:
Thank you, your son basically said what I was going to say. For whatever reasons, German cars do tend to be complex to work on, and also the parts tend to be a lot more expensive as well. Fuel pumps on some cars are relatively simple things to replace, but there are cars where they are buried under a ton of things to be removed, and are time consuming, and that costs (a typical service center in my area are over 100/hour easily, Honda is like 125 (dealer), a BMW dealer is probably in the 150/hour area).
I am not all that familiar with BMW’s, but if the car went in for an oil change it is unlikely that the tech accidentally damaged the fuel pump, unless BMW does something weird, most cars have electric fuel pumps IME and they are back where the tank is. In the bad old days, when there were mechanical fuel pumps, they often were driven off the engine, sometimes off the cam, or through some other actuation, but with electric pumps they generally are at the rear, so in changing the oil the tech would not be anywhere near that. If the tech pulled of a wire from a fuel injector, it likely would allow the car to start, but it would run like crap, especially if it was a 6 cylinder, one cylinder not firing would allow it to start. Given the age of the pump, that is not a big surprise. One of the things with fuel injection is it require high psi into the injectors, and some engines have a cut off mechanism where if the pump is not delivering enough pressure, they won’t allow the car to start (I don’t know about BMW with this, but being performance oriented engines, wouldn’t surprise me), so the fuel pump may have been marginal, delivering just enough pressure, and it dropped below the shutoff level and caused what you saw.
Modern cars are a blessing and a curse. They are a blessing because compared to the cars 30, 40 years ago, they are mechanical marvels in my opinion, they will last a lot longer, and in so many ways are more reliable, economical, less polluting, and more fun to drive, too , across the board. The downside is they are a lot more complicated to fix, even tho ugh you can buy diagnostic programs that run on a smartphone that use a bluetooth gizmo in the OBDII port to report the faults, it is still not easy to troubleshoot them, even changing the brakes is not as simple as it once was. Among other things, it often means mechanics resort to something that people groaned about in the ‘old days’, where they would replace parts until the problem went away, the diagnostic computers often don’t give that clear a picture what is wrong…and it can be costly. It is likely to happen a lot less often than it did in the good old days, that is for sure, but when stuff goes south it also can cost a lot more to fix.