red86man

I'm still peeling the onion. Just to recap, I found and removed the direct short to ground on the rear view mirror map light circuit. This short to ground directly affected the entire +12VDC #39 circuit and also affected the entire +12VDC #3 circuit with the VATS and GAUGES fuses plugged in.

With that ground removed from the equation, I'm now trying to isolate the source of an 80 Ohm ground on the #3 pink wire circuit. I suspect that one of the pink wires in the main wiring bundle (which runs from the fuse box across the dash panel) has a break in the insulation and is semi-grounded to a metal bracket somewhere behind the dash.

The main wiring bundle is not very accessible, unless I pull most of the dash out. I'm going to dig into it today and see what I can find. If anyone knows where I can find the common splice point for all the #3 pink wires, please let me know.

red86man

I only had a little time today to chase grounds between family holiday functions. I pulled the DIC panel and the radio out today, as well as the DIC mounting bezel, to gain access to the main wiring bundle. I stripped back the electrical tape around the bundle and only had about 10 minutes to look for a common splice / tie point for the pink #3 wires. Wasn't able to find it, but will dig further tomorrow.

I should take a picture and post a link of my dash opened up like a cadaver. It might be a little too graphic for those who have never or will never dive in there, though, so maybe not.

While I still had some daylight, I did a number of ground checks on various exposed circuits behind the DIC. I found another major short to ground - a big one - on the two green and white wires (circuit 916) that merge together on one of the starter enable relay terminals.

Several posts back, I had identified a large voltage drop on the starter enable relay - connector and relay terminal were gunked with crusty old, black, oxidized dielectric grease. Cleaned everything up, replaced the starter enable relay with a fresh new one, and, of course, it didn't start.

Now that I've narrowed the problems down to troubleshooting grounds, I pulled the new relay to check for any grounds on the terminals, and sure enough it was sitting right there on green / white, pin A. Tracing circuit 916 in my Haynes manual leads me back from the starter enable relay to the neutral safety switch and the clutch safety switch. Applying a bit of logic, I would assume that, since my car is an automatic, I don't have a clutch safety switch to worry about and that the other green / white goes to my ignition switch.

So, the short to ground on the circuit 916 is either coming from my brand new ignition switch - or more likely from the neutral safety switch, which is one of the few things left on the car that I have not dug into or replaced yet.

A short to ground on the green / white terminal of the neutral safety switch would definitely cause a significant +12VDC voltage drop and current drain on the whole starter system. It could also cause a large drain on the whole +12VDC system, as a result.

I think I may have finally peeled my way down to the final layer(s) of this onion. What a blessing that would be! Tomorrow, I'll replace the neutral safety switch, button her up a bit and we'll see what happens.

red86man

Happy 4th of July to all. Picked up a new neutral safety / back-up switch yesterday. Pulled the old switch and ground-checked the harness. Turns out the ground on green / white, circuit 916, was caused by a short to ground on the purple wire that goes to the starter solenoid. Of course, it showed up on the green / white wire from the starter enable relay harness because the car was in Park and green / white is shorted to purple via the neutral safety switch in that position.

Also noted a ground on the light green wire in the neutral safety switch harness - I'll be checking that out later on. Obviously, a short to ground on purple wire between the neutral safety switch and the solenoid terminal could cause some problems.

So, I'm going to run a new wire from the harness to the solenoid later today or tomorrow, slap in the new switch and see what happens. I hope this is going to be end of it and that I'll finally be able to drive her again. The endless troubleshooting and fixing is getting old.

red86man

Recap and update. Chased the ground on green / white, circuit 916 back to neutral safety switch. Pulled switch and probed ground on green / white (#916) and purple (#6) wires. Ground turned out to be on purple, #6. #6 comes from CINJ (Cold Start Injector) fuse, goes through neutral safety switch and on to supply +12VDC to solenoid "S" terminal.

On the flip side of the CINJ fuse is circuit #806, which goes to the cold start injector harness and the thermo timer switch. Pulling the CINJ fuse and probing both circuits for ground revealed ground on the #806 circuit. Obviously, the ground condition was manifested back to the #6 circuit via the CINJ fuse and the #916 circuit through the neutral safety switch.

So, I've now isolated the ground problem to the #806 circuit, which can only be one of three things: 1) ground on the cold start injector circuit 2) ground on the thermo timer switch circuit 3) ground on the wiring between the CSI and TTS or the wiring coming from the CINJ fuse.

Hopefully, this should reveal the root cause issue of my 'No Run' problem.

red86man

The source of the ground on circuit #806 turned out to be the cold start injector / thermo timer switch. With everything else connected and functioning properly, this ground also affected circuits #6 and #916 directly. The respective systems and components relative to these circuits have already be described in previous posts.

Drove around town to several parts stores and 2 Chevy dealerships before I found I found a replacement timer switch that I could order and have it overnighted. Part no. for the cold start injector timer switch is 14084318 - just in case anyone else ever has the same problem. I wouldn't wish this problem on my worst enemy, though. What a nightmare this car has been.

dclafleur

Was there ever a resolution on this?

Repzard

Maybe the MAF ???
Try unplugging the MAF and see if it starts.


Just my .002

red86man

No resolution yet. Have been working on my '85 Omni GLH N/A to get her tweaked up for daily driving, as I just sold my workhorse '92 Caravan to a buddy. She had 142K on her and was still running like a top. Without a doubt, the most reliable and trouble-free vehicle I have ever owned.

Unfortunately, I can't say the same for my '86 coupe. I love her to death, but she has been nothing but a headache and money pit for over 2 years. I've got to put the dash and console back together after going through all the wiring and fixing all the cracked, split and pulled-back wire insulation. More than I would have anticipated.

I'm sure the plugs are pretty gas fouled by now, so I'm going to replace them. I'm also going to disconnect the exhaust to ensure free flow and eliminate the possibility of plugged cats.

golfman2008

Its all a learning curve ! it sounds like you will eventually conquer your problem , good luck.