Does the fumes smell disappear once your tank reaches 3/4?
Your tank may have a leak higher up (highly unlikely as your tank is plastic) or the seal where the sending unit is located may be gone. What year is your car?
Points of interest: http://www.realoem.com/bmw/showparts.do?mo...314&hg=16&fg=05 http://www.realoem.com/bmw/showparts.do?mo...317&hg=16&fg=15
Number 5, rubber seal.
Here's a write up from Pelican (fuel pump change) telling you where the fuel pump is located. Pull your rear seat and check if you can see any fuel seapage. http://www.pelicanparts.com/BMW/techarticl...6-Fuel-Pump.htm
Read the article and pay attention to figure 9 and the paragraph that contains figure 9. It mentions the O-ring or the seal I mentioned above.
The e36 has two senders so you'll have to check both seals or O-rings.
Let us know what happens and hope this helps.