Postrgres data restoration problem

I'm looking for help restoring old postgres databases on a linux system
after a reinstall of Redhat (including posgresql). It's the same version
of redhat and of postgres I was using before the resinstall, but I've not
been able to get the database server to see the old databases.

The old data is stored in the standard postgres format. (No,
unfortunately, I did not have a backup.) The postgres data is located
on my system under /var/lib/pgsql. So I tried both creating a
symbolic link - setting up /var/lib/pgsql/data as a symbolic link to
/oldpgsqlpath/data, and, when that didn't work, I just copied the old data
directory to /var/lib/pgsql (that is, it ended up residing in
/var/lib/pgsql/data), which didn't work either:

I was able to connect to an old database (e.g., with psql dbname), but
when I listed the tables with \d, it responds with: No relations found.
I suspect that the data may be unrecoverable. Is my pessimism justified or
might there be a way (without spending days, that is) to recover the old
data?

Thanks very much!
Jim Cochrane