Dreaded No Start fixed (hopefully...)

[tccrab]

After the second stranding event, I finally decided to fix the problem once and for all.
I was never able to successfully diagnose the No Start to my satisfaction.
I'd chased wiring, changed relays, checked connections, checked the clutch safety switch, actually learned what the VATS system does and how to arm and disarm it, but in the end I never really felt that I had isolated the problem, or corrected it.

You just can't trust a car that won't start. Especially if you can't figure out why it won't start, only to have it start just fine a couple of hours later for no aparrent reason.
What's the sense of starting it, only to dread ever turning it off for fear of the Dreaded No Start?
It would almost be OK if I always drove it from home back to home. But gosh forbid if I ever wanted to take it to a car show or go for a long cruize and spend the night somewhere.

If any of you should experience the same frustration here's what to do.
Cut the purple wire inside the big loom just aft of the ECM. Run a hot lead and ground from the battery using #10 wire. Splice into the cranking circuit (it a yellow wire under the dash) using a #10 wire. I found the easiest place to access it is at the CRANK fuse in the secondary fuse panel under the hush panel on the passenger side. I ran a #10 wire through the door vent grommet and carefully hid it up against the firewall, zip tying it to the windshield washer tubes. I used black wire to help in hiding it.
I used a Bosch 5 pole 30/40A relay, here's a link to a common diagram:
http://www.the12volt.com/relays/relays.asp
Connect the purple wire from the starter to the normally open pole #87. Battery 12v goes to pin #30, ground to pin#86, cranking circuit (yellow wire) to pin #85.
I hid the relay just under the EMC, so that it's not immediatly visible, yet still accessable.

What my mod does is to use the 12v that originally triggered the starter to trigger a relay which allows 12v DIRECTLY from the battery to the starter solenoid. The current that triggers the starter solenoid does not wander all over BFE, under the dash, through the clutch switch, VATS, SIR, ECM, CCM, etc., etc.
When you turn the key, the starter WILL engage.
The VATS system can still shut off the fuel and the ignition so even though the car could crank, it won't start if the VATS is triggered.
The cluch safety switch is bypassed, so it is possible to start the car with the cluch out, but that's hardly a major drawback. Anybody that has starting issues usually wires that POS switch out right away.

Now if she won't crank, I've only got three possible things to diagnose. The relay I just installed, the starter/solenoid, or the ignition switch.

Cost of the project, approximately $25, and took about 3 hours to do. Hardest part was getting to the yellow wire under the dash and figuring how to get it through the firewall.
The peace of mind knowing that it will start every time I turn the key?
Priceless!

TomC
'90ZR1 #792