Thanks mbell666 and Makomagnet for your responses. I appreciate your feedback.
I have an AutoXray 6000 that read no fault codes through the standard OBDII. I ordered some INPA/Ediasbas cables to try to read the BMW specific codes and diagnostics but haven't received yet. Shipping from Hong Kong. The oil level is good.
I actually ordered a new Crankshaft Position Sensor last week and I'm just doing the fuel pressure and spark test for extra confirmation. I suspect CPS but I haven't tested it yet since I do have all the symptoms of a bad CPS. I was too lazy to pull the CPS to get the ohm measurement but I will probably do it on my day off on New Year's. It also appears to be a favorite failure point on our E39s.
From my readings from general web searches, the fuel rail does take a few seconds to reach threshold (3-5 seconds would be normal). I would assume that if there was some pressure in the rail, priming the fuel pump for 2 seconds should bring it up to 42 as you mentioned, Makomagnet. Apparently, if you run out of gas and added gas to the tank, it would take a bunch of cranking to get the gas to the fuel rail and to build the needed pressure.
I may be wrong but the case is that if you put the key to the second position, the pump primes and it's ready to pump fuel into the fuel lines through to the rails. The pump stops at this point (in a ready state) unless you proceed to crank the engine. Cranking will turn on the fuel pump again and continue to build the necessary psi in the rail. If the CPS failed, the fuel pump will not turn on during cranking and no increase in fuel pressure is seen which I believe is my case. The fuel pressure tester gauge does not increase psi even after cranking for a few seconds. But it does while priming.
I primed my pump 8 times and I was able to achieve almost 50 psi (looks like 48). My pressure guage must not be accurate if it's supposed to be 42. 8 x 2 secs is 16 secs and that doesn't sound good for me as it might indicate I have other issues to deal with. I didn't think this would cause a no start issue. Maybe more like a start and stall, start and stall issue on the fuel side.
That's a good question Makomagnet because I think based on the previous owner's receipts, the fuel filter and pressure regulator has never been changed. It's at 118k now so it's probably my next maintenance issue to tackle.
I'm kind of leaning towards it being normal like mbell666 said since the fuel pump is priming and I'm able to achieve the threshold psi on the fuel rail but it is definitely underperforming maybe from the fuel filter and pressure regulator as Makomagnet pointed out. It really helps to have a great community like yourselves. The feedback helps tremendously. Please correct me if anything stands out wrong.