From digest.v7.n605 Mon Nov 17 12:48:52 1997
From: t092986_at_telefonica.es (Juan J. Garcia Ruiz de Angulo)
Date: Mon, 17 Nov 1997 09:17:53 -0800
Subject: [Fwd: 325ix Fuel Tank]

Geoff.G.S.A.Allison_at_openmail.TCT4.pdomus.simis.com wrote: >
> Juan Jose,
>
> Hello,
>
> You posted a question a while back to the BMW-DIGEST about your 325ix
> fuel tank. I have a similar car, a 1989 325i touring, with the same
> tank arrangement.
>
> Did you solve your problem and what was the answer? I will shortly be
> changing my fuel pump so wanted to know how it all works!
>
> Any info would be most welcome, Geoff.

Hello Geoff. At the end I fixed it. It was some dirt in the zone where the inner tube narrows itself.

The fuel tank is something like this:

                ____-1-____________-2-____
                |        ________        |
                |   A    |      |   B    |_r
                |_|s__|__|      |________| 

The tank is filled into part A, and if sufficient fuel is poured, it flows over to part B end the rest of room over both parts. The pump and a level gauge (with the switch for the reserve light also) is mounted in the hole -1-, and a second level gauge is mounted in hole -2-. The pump gets the fuel from "s", and the return tube is connected to the tank in "r". From "r" to "s" an internal metalic tube runs through the bottom of B and over the bridge to A, ending in "s". Just in the bottom of B the tube has a zone with his diameter reduced where a Venturi is constituted. Just in the part towards "r" of the Venturi there is a hole (about 6 mm diameter) facing to the very close bottom of the tank, and that you can not see from -2-(I used a little mirror to discover it). When the returned fuel runs though the Venturi, it "sucks" the fuel of B which is carried to A. When this does not function because the narrow part of the Venturi is clogged, fuel remains in B, even when A is getting empty, with the reserve light on, and the level indicator showing near 20 liter!.

Juan José