Havent looked into the X5 tank, but most EFI systems have two pumps. A low pressure pump that picks up fuel and tops up a surge tank. When full the surge tank overflows back into the main tank. Then they have an immersed high pressure pump which supplies fuel to the engine. If the low pressure pump has failed then fuel can only slosh into the surge tank so the high pressure pump can run dry.

General layout is a barrel shaped pump assembly that is immersed in the fuel tank. This has the high pressure pump inside it, and a lower pressure on the side of it.

Sometimes the low pressure pumps have a plastic mesh bag than hangs down from it and reaches the bottom of the tank. I've seen these filter bags drop off inside the tank so the low pressure pump cannot reach the last inch of fuel.

Good luck.