I have just finished changing all my fuel lines on my 96 e300 and was hoping that my car would start. After purging all the air out of the lines i noticed that when i started to turn over the motor the fuel was being pushed backwards into the tank. All of the lines are in the right place so why is my fuel going backwards.

 

Well i finally got my E300 running....
it was a bit unconventional but i could not crank the motor long enough to purge all the air and the fuel was draining back into the tank.
so while the intake was off i put some fuel into the intakes and started the ar a few times and after the forth time it stayed running and all the air is now out of the fule lines.