Hey Pilots!

I write here because I cant open a new thread and I read this thread because I am new to the CS727 and I wanted to know how the fuel distribution is working...
but now I have the problem that my engines run out of fuel on every flight (all three at the same time).

My fuel load:
8000lbs in LEFT - CENTER - RIGHT

After startup I had all booster pumps ON and all the Crossfeeds OPEN (Selector is Vertical).
The Engines take the fuel just out of the center tank, and when the center tank is empty, all engines die.

Any suggestions for propper management?
FSX Gold Edition and the newest version of the 727 - SP 2.7

Thank you very much