Well.. I changed the coil wire. No change. I bought a new coil and put in on, no change. I went thru the diagnostics for 'no spark' in the Haynes. I'm not getting any A/C current at the Ignition Control Module at pin "B" during cranking. The Haynes says that I should take the ECU/PCM in to the dealership. However, this is the 3rd PCM and it's behaved the same with all 3. I fear I have a wiring short. When I bought this car, it had a Viper C60 car alarm system. When the motor was built up to a 383 by the prior owner, the Viper had a short that prevented the horn from blowing. I found some Viper fuses under the dash and took one out and the horn started working again. The car had ran fine till this most recent incident. Maybe there's another wiring issue with this Viper setup. sigh... I've been trying to find a wiring schematic for this much hated system so I can take it out. So far, no luck.

 

under the dash near the passenger footwell there is several relays mounted above where your feet go. any of them crap out it wont run.

 

I've seen the relays, assuming you mean relays for the <muttered expletive> Viper system. I'll check those out. Thanks for the heads up!
Here's the website the prior owner put together for my 'daily driver' while my '96 is getting it's new 383.
http://www.9t4z28.com/menu.htm

 

no no not the viper ones. factory relays.

 

Well, per Shoebox's pinouts, I checked my expected voltages against my measured voltages at the PCM. Of note, the Opti's *expected* supply voltage of 12 volts on "key on" was not met. It measured zero volts. Also, two reference voltages of 5 volts each were not met, measuring only 0.25 volts. This is with a full battery, no electric water pump running, etc. If you care to look (and you can use this for your own diagnostics since, if you key in your own measured voltages, any disparities will be denoted) at my excel spreadsheet, tell me what you think could be wrong. I still think it's a main harness short via a melted insulation somewhere.
The spreadsheet is only 47kb.
www.taekwondoplus.org/z28/diagnosticPCM_94.xls
Does anyone know what those parenthesis values refer to in perhaps a footnote? I know some are variable or A/C values, etc. I'd like to know if you guys happen to have knowledge of it.

 

Still hunting for the elusive reason my car won't start.
Here’s what’s been replaced so far;

1. Coil wire
2. Coil
3. Ignition control module
4. Optispark

Still no spark at the plugs. Admittedly, after installing the opti, I hooked up everything except the
1. IAT
2. MAF
3. Temp gauge on the water pump
4. Fans

I left those disconnected in order to quickly test if the Optispark replacement had fixed the issue.

Would having any of those disconnected cause the ‘no spark’ problem?

Thanks,

 

Well.. I sit here perplexed….
After having inspected the plug wires, coil wire, fuses, voltages and finding nothing out of order, I replaced the PCM. That didn’t have an effect so I replaced the *usual* suspects of the Coil, Ignition control module, Optispark. Still no spark. During all this, the SES light has stayed illuminated with the key in the “ON” position, no matter how many ways/times I reset the PCM. VERY frustrated, I went out this morning, rechecked the voltages on the ‘Black’ PCM connector. The red/black wire is a distributor(Opti) feed with 12 volts typically but mine has .21 volts. WTH? Then, as per Haynes manual diagnostics, I disconnect the ICM connector and probe the terminals A and D. Both measured the desired 12 volts DC. I then switched to the A/C mode on my multimeter and tested terminal C during cranking. It *should* measure 1 to 4 volts A/C. It delivered nothing. Sigh.. so I decide to quit pussyfooting and start pulling the wiring harness looms leaving the PCM apart, looking for burnt/shorted wires. I didn’t see anything. So, with the recommendation from another list member in mind, I pulled the underhood fuse box out and apart, looking for corrosion as he’d intimated. I pushed the wires around a lot since visibility is marginal due to the tight confines and abundance of wires. Seeing nothing obvious, I reassemble it and put it back in place. Hoping that perhaps just moving all the wires around might have disengaged the short(if that was indeed what it was), I engaged the remote start. Well kiss my a**…. The multimeter shows A/C voltage at the terminal C of the ICM. I get the water pump (for it’s temp sensor), MAF and IAT sensor, connect the ICM, plugging them all in and then engaged the remote starter. Vroom! She starts up. I’m happy for a moment, then it dawns on me. I have NO idea why it’s running again and therefore, I won’t know if I can rely on this car to drive in traffic and NOT die. I went into the car and checked the SES light. It does the bulb test and stays on for only a second, then goes out. Well, I can at least go ahead and reinstall the Water pump, Harmonic Balancer, fans, etc and continue to research the wires. It appears I've spent a lot of money for no improvement.
a. PCM = $139.00
b. Coil = $17.00
c. ICM = $89.00
d. Opti = $295.00 new, in box, from listmember plus shipping
e. Harmonic Balancer puller = $24.00
f. Gaskets and seals for Water pump, timing cover = $24.00
g. Coolant, silicone sealant = $12.00
Thanks to all of you that offered suggestions.

 

There is a device called an "ICM (ignition control module)" that receives an A/C (alternating current) voltage that fluctuates between 1 and 4 volts. When the voltage drops to 1 volt, that's the car's computer demanding a spark be sent to the distributor. Well, sometimes I would measure it with the connector off and it was getting the right voltages (1 to 4 volts). I'd then reconnect it and it still wouldn't run.
However, today when I pushed a straight pin into the fully connected connector and hooked up the multimeter to it and then cranked the motor, the car would start.

?????

So once it was running, I began to suspect the actual connector and began grabbing the connector housing and wiggling it. The motor would stumble sometimes, others, it would flat die.

So after doing this a few iterations to prove I could reproduce the problem, I pulled the connector apart and looked to see if the crucial white wire was broken inside the housing.

Nope, it was fine.

I then rotated the connector to look at the point where the female and male pins slide over each other...
Aha.....
The female side of the white connetor was just this much ' ' farther apart than the other 3 female connectors.
Using a pinpointed voltage detector, I pried the pin housing closer together.
I then reinserted the connector and started the car.
After that, I wiggled the connector housing over and over and it NEVER stumbled or died.

Turbo_Z correctly diagnosed the issue in general by suggesting it could be a connection issue to either the coil or the ICM.

 

Glad you got it straightened out, but I bet you are more glad.