SOS...tach help
 

First, hi to all here, and thanks for any help in advance! My son purchased a 1990/f350 dually with 7.3 International idi beginning winter and runs very strong. Had to replace #2 injector line along with main line from filter/separator to resolve fuel leak, done. Now two items stumping us...one is tach which rarely would work so based on info from here( thank you) did find bad wires from sender and ordered and replaced. Still not so much. Checked ohms and traced wires to plug at right fender under hood,OK. Now my question is, this truck originally had auto trans but was swapped out to 5 speed zf5 by po and old connections trans are under truck. Is there something we can, should, be doing there in regards to possible connections relating to these as I have read that on auto trans tach was also run to trans?! Any help appreciated!
I apologize if I'm being windy just trying to give all info to assist the forum in assisting us.
Second issue is water in fuel light. Replaced water in fuel sensor ( sm. black 1in plug in) below seperator but have read on here that there should be elec. connector/plug at bottom of same. The only two connectors are round on what I believe is fuel pressure sender and am. oval connector that I read was fuel warmer? Please help if you can, I'm stumped and son can't believe it...Thank you :s:

Nothing? Know one?

the tach is usually the sending unit
as for for the water fuel sep. ihave no clue i just bypassed mine

Thanks daves3940
Found the water in fuel light on because previous owner had wire for sender on separator housing on am terminal on alternator....go figure.
Replaced and tested sender and wiring up to gauge cluster..gonna go in cluster next and check tach itself.