Tach Doesn't Work

When I got my 72 911E the PO had removed a non functioning Perma-Tune CDI and just ran a coil and points. I just put in a new Perma-tune (the one that is for pre-70 911's cause I was missing the stock wiring harness) Car runs great. Hope it solves the fouling plug problem. However I can't get the tach to work. Wiring diagram shows tach wire as black wire with purple stripe. Perma-tune instructions says to hook it up to the yellow wire on the perma-tune harness. Didn't work. Tried to hook it up to the white wire on the harness (optional tach hook up) still doesn't work. How can I test the tach to see if it is some other problem? Thanks.

Kurt V
72 911E