I'm not sure how close in detail any diagram from Freightliner would be as some items may have been re-located by the coach builder.
But calling Freightliner's free help line with your chassis serial number , should be your first step.
Sorry I don't have the number handy at the moment .
1-800-FTL-HELP ??
A fuel strainer as detailed in this post , might be in the harness ( frame rail) above the passenger rear air suspension bag.
http://www.irv2.com/forums/f26/the-t...er-328852.html
I have fuel line connections at that location , but a previous owner may have removed the strainer.