what this part does? 16116759836

I know where it located,but i can't figure it out what it does in term sending fuel from where to where? What does keep the fuel pressure in fuel line after car is off ?. I have first poor start in the morning. it starts right the way but RMP goes up to 1000. When i start 2 time it jump to 1200-1300 with powerful start and then go to 600 right the way. All new filter, pump good gas always 93. Thank you guys for any suggestions.

it looks like that is the pump that sits in the fuel tank and sends fuel to the engine:

http://realoem.com/bmw/showparts.do?...16&fg=15&hl=11

I believe that the pump keeps the system pressurized even after the car is turned off, and a bad fuel pump will slowly bleed off the pressure thus causing longer starting times as pressure builds up.

In all honesty, I would check the battery's health because it sounds like the car is revving a bit hard on a cold start to help charge the battery to get power to electronics.

Thats what i have now sometimes and my battery is new but not registered to the car im getting it done on friday when the battery was new and just installed it was all fine.

It is #4 on diagram and it located on driver side with tubes ends at pump end. Tube is about 4 feet long. The pump starts to work when ignition,but then we have pressure regulator in the filter. When i goes to fuel rail it has no return hose, it is one way hose .

i cant understand

what is your question ?

Isn't that a fuel syphon?

The fuel tank is a saddle type, it straddles the propshaft, the tank only has one fuel pump on one side of the tank.

The fuel pump sucks fuel from one side of the tank feeds it to the pressure regulator and the excess is fed back to the tank, this is where it enters this piece and as it flows through is draws fuel from the side of the tank without the pump and feeds it into the side with the pump.

The fuel basically is siphoned into the pump side by the return line from the fuel pressure regulator.

At least I think that's what it is!

Stuart