If this is a W210 - seems like your shutoff solenoid is not allowing fuel or somehow the fuel has drained off (bad check valve in return line)

If this is a W124 - its the check valve at the fuel return which is allowing siphoning due it being stuck.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)