gm hei no spark?

The mag pickup gives a transient signal. As the distributor spins slower, the signal amplitude gets much weaker, eventually not triggering the ECU. The amplitude also depends on the reluctor gap. You can't see any of that without an O-scope. Best you can do w/ a multimeter is measure the pickup output in VAC mode (should be >1 VAC). Try to reproduce how fast the distributor will spin when cranking the engine. I would guesstimate cranking speed is >2 rev/sec (120 rpm), so 1 rev/sec for the distributor. Spin it by hand like that and verify spark. It might just be that your reluctor gap is too large or the engine is cranking too slowly. BTW, Chrysler later changed to Hall-effect pickups (even in later crank sensors), which are better since DC-accurate and give the same strong square-wave at all speeds.