Fuel scavanging sound from fuel tank

[MarkM535i]

Ive noticed when my tank is just below half full (on the 'accurate' dash gage there is a scavenging sound coming from the fuel tank, sounds like the in tank sender unit is struggling to 'pump' fuel. must admit im unclear if it is actually a pump or just a level sensor. Im wondering if something is blocked or fallen off. If I fill the tank, sound goes away, all good. If I run it really low, but still above min red line, sometimes I have issues starting the car. Any ideas before I dive in and remove it, hate messing with fuel tanks


(forgot to add it was converted to M30B34 about 10 years ago, don't know if that helps, probably not but worth mentioning)

EDIT, the car used to be a USA 528i beofore m30B34, so in the Haynes manual it says 'remove the nuts and remove the predelivery pump, then remove the screws and remove the unit and gasket'. So im guessing my car does have a 'pump' in the tank.

[Lenny D.]

So im guessing my car does have a 'pump' in the tank.

Likely, but your complaint is more likely due to the fine mesh screen that needs periodic cleaning if you do have the in-tank pump. Classic condition of noise from a fuel level below half tank. Clean the screen before you toast the pump.
And plan ahead to replace the round gasket where the sender assembly attaches to the tank top . . . and freshen the hose ends, they're likely cracked . . . and will be too short once you get to good hose.
A M H I K

[MarkM535i]

Thanks Lenny, will get the gaskets first, I have hose and fuel injection clamps so once im all tooled up, will go to work on it.