88 735iL - Won't start, fuel delivery problem?

So randomly my 88' 735il wouldn't start. It would crank and crank (the cranking was strong and sounded normal), but it just wouldn't start. Finally after turning the key to the "on" position and leaving it for awhile and pumping the accelerator a bit, it would turn on. Once this was accomplished, it would run perfectly as if nothing were wrong with it.
I replaced the fuel pump and the fuel filter, and for about a day it was working normally, however later on, the problem came back. I can usually get it to turn on (after multiple attempts and some hair pulling) about 95% of the time, in which it will run perfectly. The pump and filter were replaced about 4 days ago. I've heard of new pumps being filled with air, and that it may just need some time, but I also am suspecting the fuel pump relay. I checked the fuses and they all seem to be in working order. I was about to buy a new fuel pump relay, but then I was told by a mechanic that if the relay were bad, the car would simply NOT start. Period. Is this true?
I'm worried that it could be a vacuum problem, or worse, electrical; not giving any power to the actual relay (but then again, wouldn't the entire ebox not receive power?).
I'm kind of running out of ideas, and it's incredibly inconvenient. I feel like most mechanics either aren't knowledgable enough about BMW's, or are just flat out crooks (I would really like to NOT have to take it the dealer).
Any suggestions on what I should do? I'm assuming it's not a spark plug problem, for it will fire, and the car will run perfectly (although there is a slight loss of power I think).
Anything you can tell me will be GREATLY appreciated!!

the first thing to do is see if theres fuel getting to the rail when its not starting. then check for spark.