Car stalls when gas tank gets to half full, then starts back up

My best stab at it would be: The power to the fuel pump or the fuel pump, rusty wires if driven in salty winter conditions, I dont know if thats the case Let me know. Or even could be a problem with a sensor detected by the ECU/ECM. Also might be the fuel filter, very cheap and good to change often either way. If its High mileage then bad plugs could contribute but have no relation to why it seems to happen @ half tank. Air filter would also be good to check it costs nothing to yank it out and make sure there is no blockage around leaves, plastic bags. Try running High test gas on your next couple tanks, it will improve the combustion. It may sound like alot here but start with the cheap and easy stuff try it out.

This just happened to my 2005 BMW X5. Originally I was smelling gas on just the left side after I would drive the vehicle. I took it to a mechanic and he discovered and replaced the siphon unit which according to him was leaking under pressure only from the bowl portion. This unit distributes gas from the left side to the right side of the gas tank, which is required after the fuel level falls to approx. 1/2 tank. The unit was installed improperly which lead me to this discovery. Either the gasket was pinched or the siphon hose got dislodged. Either way, under computer hookup and analysis if the right side tank isn't receiving fuel from the left side its most likely the Siphon unit.

Did you ever find out why? Our 2011 BMW dies at half full.