From digest.v6.n762 Thu Jun 12 08:44:25 1997
From: "Brett Anderson" <Bretta_at_webspan.net>
Date: Wed, 11 Jun 1997 22:15:27 -0400
Subject: Re: E36 - Bad fuel gauge !! Help!

>
> From: "VTECMAN" <redline_at_cadvision.com>
> Date: Wed, 11 Jun 1997 08:28:00 -0600
> Subject: E36 - Bad fuel gauge !! Help!
>
> I have seen info on this before ,but never thought
> much of it ,until now. The fuel gauge in my '92 325i is
> bad!!! The gauge seem to have a ghost in it.
> Sometimes when I fill up, the gauge stays on the empty mark and takes
> hours before it will show the proper level.
> The gauge is also very poor at telling what is really in the tank. I can
> often drive for two days without it moving off the full mark.
> Any ideas? Any recalls or service bullitins?.
>
> Thanks
> Rob
>
>
>

Fuel gauge problems for the E36 have been discussed in detail in the past, there are three possible problems that have been seen on a some what regular basis, first a cluster problem, fixed by replacing the cluster. Second, a dead spot in one of the senders, or a bad float. Third is corrosion problems with harness connectors on top of the sender units, they sit in a hollow and can suffer in extreme weather climates.

The gauges of all BMW's, for as long as I can remember, have read full quite a bit longer than the tank is actually full, the float at its maximum height remains submerged in fuel until the level drops considerably, the theory is that if the float has less travel, the resistance values can be more precisly transferred to an analogue gauge, making the gauge more accurate once it begins its travel.
The proof of the theory is that even though the gauge does not move for a long time after filling up, it very accurately represents the level when the tank is in the last 1/4 .

First thing to check when trying to identify the problem is the connectors on top of the senders, if they are clean, fill the tank to the point where the gauge dies, then check for resistance to ground on the senders, if one shows an open circuit, that is the culprit, if not , allow the fuel level to drop to below half, then remove the senders and again check resistance between the two pins while sweeping the floats through their arcs. If nothing is found, reinstall all, and remove the cluster, ( best left to a professional as it requires removal of airbag ) and check for the appropriate resistance into the gauge, if its ok, replace the cluster

Brett Anderson

BMW and ASE Master Technician