Mike
The following method works on all BMW's using a cold start valve. On tii's always allow 5-7 seconds with key in run position before cranking, as this allows fuel pressure to build and stabilize. Cranking before this only runs down the battery and grinds on the starter and flywheel.
Sounds like lack of cold start primer shot. For a test, get a pair of miniature female spade clips and build a test harness for the cold start valve.
Disconnect the blue plug fromt the cold start valve and clip a ground wire to one lead (-), and a hot (+) to the other while a friend is cranking the engine over.
If adding fuel fixed the problem, by-pass the thermo-time switch mess and relay a cold start system from the parking lights, or something else you can control.
If adding fuel doesn't help, see if installinng one warm spark plug does. But that's food for another article.

Dan Patzer the CyberWrench from BIMMERS ONLY 72' tii touring K75RT 85' 732i R1100GSA R850R http://www.nwlink.com/~bmrfamly/ 425-259-3601 O.E.M. parts, Independant service since 1967 12724 Marine Drive, Marysville, Wa. 98271