Could be a "Cam Position Sensor"... about $130 on line. Located on front of motor, requires a 10mm wrench to replace. I've been told to carry one, haven't needed it yet. I've had my 2001 PS for about two years. Good luck.
I have just encountered a similar problem with my '90. I can hear the solinoid clicking but that is it. I successfully jump started it and drove home with the amp meter very low. Once home I cleaned the battery posts, etc. but it would not start. I put a charger on it and it accepted a charge and eventually started with the charger on engine boost. After driving to the airport and parking, it again would not start. I pulled the battery and put the charger on it and found it was fully charged.
I have not tried to start the vehicle again however, I am not hopeful. The battery is only 2 years old and has never been completely discharged before.
Is there an inexpensive way to diagnose the problem? Battery, alternator or ?