Air in fuel return line

[NashTom]

840 with new bmw fuel pump and other side bmw sending unit and all new hoses on tank. I occasionally get a large amount of gurgling air noise from sender side of tank at start up. I would think that a failed check valve in a pump would be the reason but does not seem likely in a brand new pump. Am I missing something here? Or is the brand new pump check valve bad? Can the FPR be damaged and let air in but not hurt performance? This is my first 8 and first BMW so I may not be the best judge to say it is running correctly but it sure feels smooth.

[Timm]

If you have a leak (air or fuel) between the pump and the FPR you will get long cranks if the car is not run for a couple of days. If you have normal cranking then it will be a small leak in the return line from the FPR to the tank.....

[NashTom]

Thank you Timm. It appears to be normal cranking. I expected to smell fuel if there was a hole large enough for air but smell no fuel. I planned to continue changing hoses anyway so I will start tracing the feed and return to replace rubber lines.