Hello, I'm new to this forum.  Looking forward to getting lots of useful and helpful information about my BMW on this forum.  

I have a 2000 528i and I've got a problem with it now and thought that someone on this forum would be able to assist me in fixing the problem.  My BMW has always been very dependable over the years that I've owned it.  However, yesterday when I went to turn it on, it ran for about 5 seconds really rough as though it was only firing on two or three pistons and then it stopped.  I tried to turn it back on but it wouldn't start at all.  It's never been like that before.  I was out of town and it sat for three weeks since I drove it so I have to wonder if that may have done something to it. It had run flawlessly the last time that I drove it before the three weeks that it had sat.   The battery is not weak or dead.  When I try and turn it on, I hear a slight humming noise in the back seat area which I'm thinking is the fuel pump.  I've heard that sound every time I turn it on.  So I think it's not the fuel pump or fuel pump fuse(s).  I then noticed that when I used the remote to lock and unlock the car, the alarm wouldn't do the usual chirping sound.  I disconnected the battery for a few minutes and then reconnected it and went to try and start the car again.  This time the alarm chirping sounds came back when locking and unlocking the car before attempting to restart the engine.  This time when I tried to start the engine, it did sputter for a few moments and seemed to sound like it was backfiring a little bit but then it wouldn't run.  What it does now is it fires right up but seems to run for a second and then stops running like I've just turned off the engine.  I had a similar problem a few years ago and it was just the cam sensor which I changed.  I've also replaced the fuel filter in this car about a year and a half ago, unless there is a second one on the car that I do not know about.  The one I changed was under the driver's side of the car and was a metal cylinder about nine to twelve inches long.

So would anyone know what the problem would be with my BMW?  I'm sort of wondering if it's the fuel pump.  If so, where is it  located and how do I get to it (if I have to remove the back seat, how exactly do I do that?)  Would a bad cyclone separator cause this problem?  Where is the block of fuses for the car located?  I notice a few fuses right above the battery in the trunk space on the right rear portion of the car, but there has to be more then what I'm seeing, I only see about five or six fuses there.

Thanks for your help, I'm looking forward to any help that you could give to me.  And I'm happy to be on this forum.