Unless you're sure of what you're doing, stay away from playing with the amp setting. At best you'll pop fuses in the meter.

Volts is all you need.

Since I am not familiar with it, I'll stick to voltage. Thanks for the heads up.

The big issue with measuring amps is that you have to install the meter in line. Meaning, disconnect something and join the circuit back together so power flows through the meter.

There's some meters that have a clamp that measures the magnetic field through the wire but you need to be able to get the clamp around just that one wire.

But you need to be able to monitor what the V is doing when the problem occurs, AND when it doesn't. This can easily be accomplished by running a separate (jumper) wire inside the car from the Start terminal on the solenoid to your voltmeter.
It does not have to be a large wire as it will not be carrying any current. Make sure your connections are at both ends of the jumper and the meter has a SOLID Ground.

Very simple and EASY to do. it's the same as the light bulb test except you are looking at the meter reading rather than the brightness of the bulb.

I tested the mounting area for the starter and where the negative cable mounts. Both show 0 for resistance and test light for ground lights up. Problem with a jumper wire on the start terminal is there is no room with the IGN and bypass wire on it. If the car doesn't start with the key, I will try and read voltage as well as look at the test light set up at the NSS. The key usually doesn't work for like 3-4 tries and then I use the bypass button. The test light and multimeter get grounded at the parking brake and it's a good ground. I like the bulb idea because it's sitting on the console and I can't miss it and it should remind me to pay attention and test it. Maybe I'll see if I can get 3 ring terminals on the start terminal while it's off the car, but I'm not sure if I can.

Did you already reinstall the starter? Why? It's just in the way now.

We've already determined that you have close to a half volt drop from battery to starter, WITH THE STARTER REMOVED.

That's your problem, now we just need to figure out where you're losing the voltage.

We also know that the voltage rop affects both the original wiring AND the bypass, therefore the problem is upstream from those.

Measuring resistance isn't accurate enough. A single strand of wire can show zero but clearly won't pass enough juice for anything to work. And at this point there's no indication that the problem is with the ground side.

Have you done a visual inspection of wiring under the dash? Look for things like discolored or melting connectors and insulation. High resistance causes voltage drops AND heat. Enough heat to burn or melt things.

This is what I'm trying to lead him to. From the readings he's provided the fault is in the crank signal circuit. Or, more specifically the power supplied to that circuit. He's measuring a half volt less than battery on both the original and bypass, where's that half volt going?

At some point, he's going to have to get uncomfortable and start poking under the dash. Pro tip, remove the drivers seat!

Next step is to try to trace the wire from the junction block to see where it has the first connection and check voltage there. I found a wiring diagram, but trying to see what one goes to power the fuse block is like reading a foreign language. I figure see where it goes and find a spot to measure voltage at. If it's battery voltage at the first point I find, I'll keep going.

is that .5 volt static or with a load?
on Most GM's the battery power comes from the starter stud. The + battery cable goes from the battery directly to that stud. Another 10 Ga wire is on the same stud that feeds the electrical system.
There are some variations in which an "extra" 10 ga wire comes from the BATTERY positive cable connection to a "jumper' stud usually near the battery. They can also be a problem area.
I hope to God he doesn't have the 2.00 bolt on replacement cable ends as they are notorious for causing this exact issue

is that .5 volt static or with a load?

____ from what I've gathered of his description, this was a disconnected wire at the time. That's why I'm emphasizing backtracking the circuit to find the power loss.


on Most GM's the battery power comes from the starter stud. The + battery cable goes from the battery directly to that stud. Another 10 Ga wire is on the same stud that feeds the electrical system.

____ I've seen this design on various GM vehicles but haven't worked on something this old for a long time. So, I'm not sure what setup he's got. I've also seen fusible links at the starter.

There are some variations in which an "extra" 10 ga wire comes from the BATTERY positive cable connection to a "jumper' stud usually near the battery. They can also be a problem area.
I hope to God he doesn't have the 2.00 bolt on replacement cable ends as they are notorious for causing this exact issue

____ maybe, maybe not on the cheap clamps BUT he's got adapter to go from side to post style cables. I've also seen really poorly made aftermarket cables, like didn't strip the insulation before crimping the ends.

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Can you scan and post the diagram?

Don't feel bad about struggling to read the diagram, they take some getting used to. Borrowing your kids colored pencils can help, trace or highlight the suspect wires. After 40 years, I still do this.

Start at the crank signal wire (starter end) and work your way to the NSS then the ignition switch. Find the fuse block terminal the bypass is wired to and work your way back as well. Eventually these two will end up at the same place.

Speaking of ignition switch, is yours on the column or dashboard? This is the era where that change was made.

Battery is side post with adapters for top post cables. The only long enough 2ga cables I could find were top post. Factory lead ends, not add ons.

Battery runs to starter on large cable and 10ga to junction block. Junction block and battery are same voltage.

Starter is out during all this testing.

Ignition switch is on the column. I have not tested voltage there.

Bypass is wired to the IGN prong on the fuse block.

I'll see if I can scan the wiring diagram today and post it soon.

Found these online someone took. I saved them. Not sure how good they are. There are more, but look like rear of car and AC wiring.

This one shows the fuse box as well.

The last one is all AC related, not needed right now. I downloaded the others and will peruse them later.

Thanks. Took the manuals to work I have and printed out what looked like under hood and front end wiring. Will have to scan them at home hopefully the next few days. Looks slightly different, probably a different book. Wiring looks the same on both from what I can tell.

Yeah, I emailed them to myself so I can print them out.

The bulkhead connector was confusing at first until I figured out that the 2 connectors pictured NEXT to each other didn't connect TO each other. Their mates are on the other page.

Besides the bulkhead, I seexa splice near the alternator and there's the junction block which I guess is on the inner fender or core support.

I'd like to find the splice, it's a good test point and potential failure point. 50 year old underhood wiring can have issues.

I scanned some in higher quality if you need them emailed. Just let me know. I have them in JPG and PDF formats. I don't know what's on the alternator wiring to be honest. I do know there's a junction block on the core support near the battery. I know it's getting close to the time I put the car up. Usually in early October. I have to change the oil and a few other things first. If I can not get it figured out by then I will have to put the starter in it to do the stuff for storage and drop it again an trace wiring or just check for voltage at different points and don't start the car. Not a fan of letting it run during storage as I won't drive it once it's parked. Hopefully I can figure something out by then. I plan on putting a 12ga wire on the solenoid starter stud along with the stock IGN wire and bypass wire to check voltage to it while I'm inside the car. Was going to use a U shaped one instead of a ring. That way I can hopefully loosen it and remove it without dropping the starter. I know the battery voltage is getting lower each time I mess with it. But even if the battery gets to 12.4V or so, that's the number I'll be shooting for at the other points. I may have to recharge the battery once in a while. It is only 2 months old, so I know it's good. Just don't want to wear it out too much with testing.

I tired reading the diagrams and seems it runs from the junction block to the horn relay at the drivers side core support next to the voltage regulator. Not sure if it's in line before, after, or even in line with it. But the horn relay is 0 for resistance and battery voltage. Not much time to mess with other stuff tonight.

Your first pic is of the engine compartment wiring.
You need to check what the V is doing under a load.
If ONE strand of a 10 ga wire is intact it will show ZERO resistance.
It will also show battery voltage
BUT it will NOT pass enough Current for the solenoid causing the V reading to drop significantly.
This is why you need to monitor the V under a load via a DVM or light bulb
I would clean both of your side post adapters where the attach to the battery AND where the cables attach to them. Also clean the cables themselves.
Next inspect and clean the junction block and terminals.