Ok, first round of tests today:

1. Checked DCR from the negative post to ground, still getting that strange -18Ω reading
2. Checked DCV from the negative post to ground, as expected 0 VDC
3. Checked DCV from the positive post to ground, as expected 12.46 VDC
4. Checked Relay Control VDC at rest to ground, 12.46 VDC, no loss
5. Checked Relay Control VDC under load Lights On only, 12.09 VDC
6. Checked Relay Control VDC under load Lights On Cranking Motor, 10.08 VDC
7. Checked Battery Positive VDC to ground under load Lights On only, 12.12 VDC
8. Checked Battery Positive VDC to ground under load Lights On Cranking Motor 10.08 VDC

From this round of testing, the battery tests good under load. I am still at a loss at this point. Three thoughts:

1. The battery appears to be good under load, but the chattering ASD prevents startup
2. I would like to throw in a new battery, but it is the equivalent cost of a new fuel pump assembly, should that be the culprit
3. A new battery can't hurt, given the age of the current one

I have not tested the ground side of the ASD Relay Control Circuit - the PCM switches that and should pull that point down to chassis ground. I will have to test that with both the relay in and out of the circuit. Results to come. Here are pictures of this round of testing:


ASD Relay Control Voltage at rest

ASD Relay Control Voltage Headlights On

ASD Relay Control Voltage Headlights On Cranking Motor

Battery Voltage to ground Headlights On

Battery Voltage to Ground Headlights On Cranking Motor

 

Check that the PCM has good grounds. Should be able to find a wiring diagram here. Yes, it's a russian site, but, I have been using it for quite some time now, without issue.

 

Thanks so much for this link!! I literally just sat down to try to figure out where the PCM is grounded. I may end up driving around a Russian spy satellite, but hey! I will take the information at this point.

 

So it looks like the PCM has two main grounds, one of which I have not checked. Here is the diagram:


I cleaned up the lower ground to the block. I will check the fender ground.

 

Fender ground looks good, I will have to disconnect the PCM harness to test the connector.

 

I remain stumped. I repaired some more bad grounds, checked, cleaned and reseated the PCM connectors. I haven't checked the interior fuse box yet, just to be thorough. I think the chattering noise is coming from the ASD relay, but the noise is pretty loud and echoes around in the engine bay. These old ears cannot be sure - there could be another device under the hood making the racket. Now that I think about it, it does sound loud for a relay. When I remove the ASD with the key on, the noise goes away and returns immediately when I put the relay back in. I also unplugged the TPS, IAC and a couple of other devices, no change. I realize the TPS is a sensor, while the IAC is an output device that could be clattering. I wonder what else could be chattering as an output device? I even removed the bottom relay box cover to check the connectors there, no problems seen. More pictures:


Corrosion and oxidation

cleaning and reseating PCM connectors, picture for identification

Bad looking crimps with oxidation

Corrosion and oxidation

 

Do you have a scanner you can plug in? Would be interesting to see what the PCM thinks is going on. I don't see any reason it would dance with the ASD like that, unless there was an internal failure somewhere.....

 

I have a simple Bluetooth code reader. I'll see if I can get it to connect and read any codes.

 

For arguments sake, what else could be making a high speed, buzzing or clicking noise, besides a relay? What other output devices are under the hood? I don't think it's a fuel injector, but it could be. Maybe I should disconnect those one at a time?

 

I think relays are about the only thing.... injectors can click, but, they are quieter.... but, essentially any solenoid or relay can make the noise.