('79 300TD; W123)

Tonight I tried to replace my manual fuel pump 'cause the original one
is leaking.  I went to the dealer, pointed at the picture, and got the
item ordered.

I went back today, 'cause I figured I needed a gasket or something.  The
dealer told me, "oh it comes with what you need".  Ok.  Back home I look
at it carefully, and no, there's no "seal ring" in the package.

Anyway, I pop the old manual pump out (not a lot of room in there for a
wrench of the appropriate size, eh?), pull the seal ring off the old
pump, and hmm interesting, it doesn't fit on the new pump.  Like, the OD
of the seal ring is the OD of the pump minus the threads.  So,
obviously, the new pump did not get installed as it would not fit in the
hole.

I'm wondering then a few things: might I have a pump from a different
car?  It looks like the pictures over here:

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=123190&M=617%2E912&GA=722%2E118405&G
M=716%2E005++++++++++++++717%2E400&CT=M&cat=143&SID=07&SGR=045&SGN=01

If I do in fact have the original equipment on my car, is there any
precedent for Mercedes giving out the wrong parts?  The part number
seems to match; the packaging I have says A 000 090 88 50, and the above
site lists two: A0000900050 and    0000908850 (am I'm guessing correctly
that the second column means, "superceded by"?).

The fact that the new one doesn't have the seal ring is suspicious, but
it seems odd that MB would have the wrong part in the bag.  There's no
way the part I have will fit.  Any thoughts?

thanks,
-tom!

--