Porsche Repair: Porsche 928 84 Alarm?, haynes repair manual, type diagnosis

Question
Dave, I have a 1984 928S.  This is a car I purchased about 8 months ago.  The car was a lot of fun for the first 5 months.  The last 3, "not so fun".  One time I pulled in the driveway and the car died.  I checked and found only 3-4 volts to the ignition coil.  Later the same day I tried to start and it started fine.  I didnt think much about it and continued to drive a great car.  Sometime in the fall, I was driving and drove over a railroad track.  The car died as if I turned the ignition off.  Had to have the car towed home and have had no luck finding the cause.  I have had Ideas like, ECU, Alarm, Ignition module,wiring, ect..  I have seen some flow type diagnosis charts online for the 944, telling how to check power at certain pins on the ECU, ect.  The car was running so good until the railroad track incident.  I again only have 3-4 volts @ the ingnition coil.  Any ideas or diagrams would be greatly appreciated.  I have to help customers and mechanics with technical questions on the phone and know how much harder it is when you can't put your hands on it yourself.  So, Like I said, any suggestions would be great.  Tim


Answer
Hi Tim, this is a tough one because of all the possibilities.

This idea may help a bit:

I'd locate and buy a Haynes Repair Manual for the Porsche 944.  It's their manual #1027 covering models from '83 to '89.  I have found it useful in diagnosing 928 problems.  I can't guarantee the wiring diagrams will be identical to your car, but they will be the closest possible.  

The manual should be in any of your local parts stores but it'll be cheaper on the internet and you can even find clean used copies on book seller sites like:

http://www.bookfinder.com/search/?ac=sl&st=sl&qi=V2EK4oBoQx79,6cMU5hes0gww5A_233...

Good luck.

Dave