Major Electrical Problems

[96Vic]

The car in question is a '96 P73 with around 100k miles on it.
The problems I'm having:
-The ignition switch will not engage the starter, I am able to jump the solenoid directly to the battery and the car starts and runs perfectly.
-The switched alternator exciter wire won't power up meaning the alternator isn't working. Again I was able to jump this wire directly to the battery and now the alternator is putting out a healthy 14 volts.
-Both ABS and air bag idiot lights are on.

Everything listed went wrong at the same time, so it's clearly connected somehow. So far I've replaced the igniton switch, cleaned and checked battery terminals and grounds, checked every fuse and relay in the car and everything seems fine there. The car will run and drive fine after jumping the starter, however that is going to get old really quickly.

Is the PCM connected to any/all of these systems? The reason I ask is because the day before all this started I had a hard time starting the car and then a horrible misfire for the first 30 seconds of so after which it ran fine. I also noticed the voltage gauge moving around a few times, the next day it wouldn't start.
Thanks for your help, I'm very close to junking this car if I can't figure out the problem.

[sly]

check the wire harnesses around the engine and make sure nothing is resting on the exhaust or is otherwise damaged. It could be the chaffing issue like RyanS had with the tank. Wire bundle that goes down from the PCM between the firewall and inner fender wore through and shorted out stuff. The no start issue could be related to that or the neutral safety switch on the trans is giving you issues. But since the airback and ABS modules are both bitching too, I'll wager on the wire loom issue.

[SVT98t]

!!!!! Check this shit out.....

I had an a condition where the car wouldn't turn over. No fuel pump or ignition. I checked the fuses, and they were good, so I replaced the fuel pump.
It didn't fix the problem.
I did some troubleshooting, and found that I wasn't getting power to the PCM relay. I couldn't find the issue, so I jumped the high power terminals at the PCM relay, and had a switch to turn it on and off.
That was in 2009.
Fast forward to June of this year, where I really tore into my car fix mutliple issues.
I found that the one of the five harnesses on the drivers side was chaffed through.
Here's where to look:


And a pic without that pesky fender and inner fender:


And this is what I found:



As the corrosion got worse, my car started stalling out in wet weather. That's when I knew I had a problem, but I couldn't locate it.

Here's the fix:


I took the entire harness that was bad out of the car and spent over 4 hours cutting and soldering in new wires. I ended up cutting out around 15" and 18" of the PCM power wire. (It leaves the PCM Relay as one wire, but splits into two. I corroded on the lower wire, worked it's way back to where the wires join, then corroded backwards down the other PCM wire)
The other wire that corroded through was the reverse lights. (My wife supposedly told me that the reverse lights flickered over the summer. Supposedly)

This was all on my 93 Grand Marquis, and the wiring *should* all be the same. I think it changed in 98.
But I really hope this helps.


Let us know how you make out.


-ryan s.