I did a flight in the 737 after first selecting the AC11 commander 114, and when my fuel reached 50%, the engines continued to run. I did notice that the AC11 has a fuel tank selector for BOTH (ALL) fuel tanks, and it was set to that before I loaded the CS 737-200 (American Airlines livery). Because I still had the J-3 Piper Cub as the default flight, it may have overridden the default fuel tank selector setting.

I saw somewhere on the CS Forum (I think it was one of the 757 Captain III forums), that using a Carenado aircraft can cause problems with it. It might be the same for the 737.