Ever wish you hadn't done something. I'm there right now. While I had my dash out of the car for replacement I decided to remove the Crime Guard 328i alarm system that had been installed by a PO. The modules under the steering column were just bunched up and rattling around down there. I downloaded the installation instructions for the alarm system and disconnected each wire in order of the installation instructions (battery disconnected). All the wires were spliced into the existing wiring harnesses by opening the insulation and soldering in a connection. I removed all those wires. Only one circuit had a section installed in series and that was the large yellow starter circuit wire. It had been cut and each end then was soldered to other wires that went to the starter interrupt relay. I used a crimp connector to join the ends of the yellow wires and then soldered them up. After everything was removed I reconnected the battery, pushed down on the clutch pedal and turned the key. NOTHING. Not a click or anything. I verified that the yellow wire has power when turning the key. The dash is still out and all the various connections for the instrument cluster, aux cluster, radio, etc. are there, but not hooked up. Could this be the problem? Is there a dash connection that needs to be hooked up for the car to start? The only odd thing that I could find is there are two small green wires that come out of the ignition switch by the larger red and yellow wires. Both of these had been cut, the two to the harness had been connected together, one from the ignition switch had tape over the end and the other had a wire extension from it to a scotch lock, but I don't know where it might have gone to. I checked all four ends while turning the key and none of them are hot so I don't think that this has anything to do with it.
None of the wires for the alarm system connect to any PCM circuit ... just a starter interrupt system with a siren and would probably flash exterior lights if activated.
I've got the factory service manual, but it doesn't seem to help. I really wish that there was a complete wiring diagram in the manual so that I could try to diagnose the problem. Those old manuals aren't anywhere near so good as the ones for new cars.
The car is totally dead and I don't know what to do. Any thoughts?
1986 GT with S@ 3800SC, 5 spd Getrag.

Check for power on the starter wire either at the starter if you can get at it or at the C500 connector to make sure you have a good connection from the clutch start switch to the starter. Also check for power at and getting through the clutch start switch

quote Originally posted by FIEROFLYER: Check for power on the starter wire either at the starter if you can get at it or at the C500 connector to make sure you have a good connection from the clutch start switch to the starter. Also check for power at and getting through the clutch start switch

Thanks. I will check those in the morning.

Fieroflyer. Thanks for the recommendation. I had power to the clutch safety switch (yellow wire), but no power out of the switch to the purple wire. I removed the switch and found that the locking clips had come off so the switch wouldn't close. I jumpered it and the car started right up. Now all indeed to do is reinstall the switch, adjust it and put it all back together. Found a nice article on the switch in the link below. Thanks again for the tip. I will sleep better now.

https://www.fiero.nl/forum/Forum2/HTML/123269.html