Restoring databases using only data/ dir

Hi,

We have run into some problems here which stops us from properly backing 
up the databases using pg_dump. We do have a tarred version of the data 
directory (/usr/local/pgsql/data) which contains databases that we need 
to restore.

I found out that simply replacing the data/ directory does no good. Is 
there another method in which I can restore databases with the data/ 
directory?

Thank you

Afra