[Formerly Steve Wilkinson]

Car is a twin-plugged, carbureted '83 SC with twin MSD ignition boxes and twin Blaster coils, absolutely no other engine electronics. Meaning it's an old-fashioned air+ fuel + spark = guaranteed ignition car. Drove just fine yesterday--totally normal, no missing, no loss of power, nothing out of the ordinary. Shut it down in the driveway. And today it won't start.

Cranks just fine, fuel pressure is three psi on the gauge, there's still plenty of atmospheric air here in New York, so I pulled one of the two coil leads and with a bent paperclip inserted into its socket tried to coax a spark, while my daughter cranked, to jump a small gap to the fan housing. (Normally, these MSDs will send a monster spark an inch or two.)

No spark. (I didn't try the second coil, because assumedly if that one's working I'd still get a start on just one set of plugs.)

Is there a failure point anybody can come up with that would simultaneously disable both independent ignition circuits with absolutely no warning or prior symptoms? The only other anomaly the car has been showing is that, since coming out of winter storage (and after hundreds of miles of normal driving), the tach is inaccurate at the low end of the scale; it seems to be accurate from 2,000 rpm up, but it usually settles on about 2,000 at idle when I know the car is doing 850 or so rpm.

Any ideas?