89 RS with 305 v8. Car was running good and no problems starting prior. Removed transmission for rebuild, during this time I messed around with under the dash wiring a little bit, but nothing major, Mostly just trying to isolate old aftermarket security system, but didn't remove anything. Also replaced Positive cable, as well as new bolt/nut where all the positive cable and fusible links connect near the battery. Got the transmission put back in as well as replacement clutch.

Tried to start, starter would engage but not spin. after a while thought it was a bad starter so I replaced it. no change. Eventually got around to jumping the wiring to bypass the neutral safety switch and then the car would crank and start but only if the clutch pedal was not pressed.

Figure that was good enough for now, next day jumped the safety switch wiring again and drove the car approx 15 minutes to my parents house with no problems. (Gauges were disconnected at the time) Got to their house and noticed it was overheating and the radiator cap was leaking. reconnected gauges and temp showed around 260. (yes im an idiot for not taking the 2 seconds to reconnect gauges before driving)

Let it cool off for a couple hours, Topped off coolant in and restarted. after getting new broken drain plug that was leaking and retopping off coolant again the cooling fans never came on. Thermostat working fine, but let it get up to 230-240 and fan never came on.

Just wanted to get it home and into my shop, so figured I would simply hard wire the fan to the battery and get it home. Now with fan running attempted to again jump the neutral switch wiring and start the car... Nothing, no starter click, nothing. Checked all fuses, was a popped acc fuse and also the cooling fan fuse. Replace both, still nothing. Reconnected fan and tried again, still nothing. All fuses under the dash are good. Fusible links appear to be good.

Im at a loss. The few seemingly unrelated problems make me think problems with either power distribution or a common ground somewhere. Anybody have any ideas on where to dig in first? The wiring especially under the dash is a **** show from before we bought it, wiring under hood seems decent.

Thanks

 

You said the fusible links appear to be good but have you checked for continuity from point A and point B on the fusible links? They can look fine but still be bad.
I would check for power in and power out of the starter enable relay and power in and power out of the clutch start switch. I would also rule out the resister on the key.

Wayback Machine (archive.org)

 

Im thinking it is likely the fusible link. I have no power getting to the starter relay on either of the yellow wires going into when key is in start position. Ill dig into that this weekend. Thanks for the reply

 

Random though........
When you removed the trans did you support the motor in any way? Have you checked the condition of the firewall to Pass. cylinder head ground? Is it possible that it was damaged during tran removal and install? Weird things happen when you loose a ground.
If no power at the starter enable relay then the ignition switch and it's wiring could be suspect.