1997 Chevy Silverado Truck won't start / run - cranks fine

History:
No codes but was getting more difficult to start when cold. There was a short period of time when truck would start immediately but later not start at all or vice versa, (same conditions – cold, not run for several hours). No other maintenance/repairs accomplished coincident with failure to start.
Current:
Will not start. Good spark and fuel pressure (60+ psi) – fuel pump is new. Will not crank on starting fluid. No check engine light. Compression is good at about 170 psi.

-Boris-