OBS: Before you start to work on the fuel system disconnect the battery and make sure that nothing in the vicinity of fuel / leaking fuel can produce sparks or like.
Quick Links: Fuel Pump Fuel stops at 1/4 tank
Fuel pump
Here are some preliminary links to replacing the fuel pump located in the fuel tank right side.
The videos by HFP show replacement by an aftermarket pump. I see no reason not to use genuine BMW parts, however the videos are very detailed and professional.
HPF BMW M3 Fuel Pump Hanger Install Instructions Part 1
HPF BMW M3 Fuel Pump Hanger Install Instructions Part 2
HPF BMW M3 Fuel Pump Hanger Install Instructions Part 3
DIY: M3 Fuel Baffle Fixture + Fuel Pump
ISSUE: Fuel supply stops at ¼ tank.
The tank has two deep sections connected with a more shallow middle section. In broad terms about ½ the tank volume lies over the shallow section and all of this content can flow to the right side of the tank, where the fuel pump is located.
When the tank is less than ½ full, the contents is located in the two deep sections, the right with the pump and the left, where there is no pump. From this level and down the pump can empty the right section, but not the left. The left “pool” contains app. ¼.
From the factory there is a transfer system, which transfers fuel from the left “pool” to the right. This system works without a (electrical) pump. It is an injector system that creates a suction effect by the return flow which is routed to the left side. It’s a venturi system.
The common failure seems to be that a hose (pipe) is disconnected, clogged or the plastic material has aged and cracked. If you plan to take the system apart to solve the problem, I’ll recommend to get a new rubber seal (Part 16 14 1 182 905 – No 4 on picture below) before you start. Leaking petrol is not to take lightly.
This video, V10 E46 M3 fuel system & brake lines - Driftworks BMW project Pt 28, basically deals with something quite different, however from 1:30 to 2:30 the siphon system (transfer system) is shown.
PS: The error can be corrected in the left side only.
