generally the fuel pumps are quiet
in general, if they start making noise then it is probably time to change them. You cannot hear them when the engine is running. Needs bridging thefuel pump relays. Or someone listens at the rear end when you switch ignition on. When you switch ignition on without starting the engine, the fuel pumps start working till they have made enough pressure in the fuel pressure line which is required that engine can start. That is usually (when the check valve in the tank is fine) just 1-2 seconds, when check valve in tank is not good, and the car has stood for example over night, it might take some seconds.
Or you use long cables from the engine room B+ and ground and give directly power to the connections inside the trunk.(or from a jump starter)
Easiest is the fuel pump relay jumping, see Johan's website, link is on my website below under DIY links private.Shogun E32 Tech Tips: http://twrite.org/shogunnew/topmenu.html
Pulse sensor if no fule pump realy pull in
If you don't see fuel when cranking ( using info from previous posts) you can bypass fuel pump relay with a jumper to test from relay socket back. I think shogun or Sean has a link on his site. If that works you could have a bad crankshaft pulse sensor. It plugs into main harness and sensor head detects crankshaft pulley rotation and to pull in the fuel pump relay. This sensor can go out all at once or sometimes not pull in at low RPMs but trick you all is okay until you stop. then no start. I think if you look hard they run around $55 to $75. You can also do a resistance check on the sensor to get an indication is its faulty. My BMW mechanic buddy always keeps a used spare one around to quickly trouble shoot things like this. I borrowed his to keep driving until my new one arrived. that was at maybe 230K mark. Good luck ! KenKen
74-Widebody Porsche 911S