Ok, repeated the test at solenoid and had 12v at the s stud Everytime. Weither it started or not. One time it dropped to 4v but only once on 10 attempts with 4-5 starting and atleast 6-7 not starting. So to me, it was likely a tiny movement/error on me moving a lead that 1 time.

For voltage test at main power stud....I get 14v before trying to start, 12v while cranking, and 16v if it starts.

This makes me think my multimeter isn't accurate, because it's supposed to be 12v normal, 10v starting, and 14v when running. Seems like my multimeter is off by "2 volts"

So I tested the voltage at just the battery terminals to see what the battery said by itself with truck not running, and it says 14.2 volts..... basically confirming it. (Was going to confirm the battery said around 16volts with it running like down at starter but after 7 tries not start, I gave up on that extra confirmation)

So if my meter is reading about 2 volts above true voltage.........it means I'm only getting 10 - 10.5 volts on purple wire....... because it reads 12 - 12.5 volts.

What next?

 

Replace the starter again. If you have 12 volts to the solenoid when you turn the key, and your sure the battery cable is healthy and suppling full battery voltage to the main post on the starter solenoid, your ground cable is good. It has to be a defective starter. Do you have a starter rebuild shop in town?

 

I'm assuming you didn't read all the posts? (Not that I blame you, it's alot of reading).

First, after last tests, I'm almost certain my multimeter is inaccurate, because I'm reading 14v at battery with car off and 16v with car running. (So sure seems my multimeter is reading "high" by about 2 volts). That would mean the 12v reading at the solenoid is truly only around 10v.......

Secondly I already put 2 BRAND NEW GM starters on it and both acted the exact same way. The chances of it being the starter is almost nill.

I also am far from confident I don't have a ground issue somewhere. I cleaned the ground from engine to firewall. I also cleaned the one under the truck, under where driver sits. (But have just found out from watching YouTube troubleshoot videos there are 2 more. One right on the driver side of engine block and 1 where the driver side front tow hook is located). Feel I need to try to clean and check these as well.

I appreciate any comments though, as I'm desperate for help and to get this solved.

 

check the ignition switch. check the power coming in and the power going out when starting position is operated. maybe your voltage drop is there. they can be opened and inspected if you'r carefull enough.

 

Remove the converter/flywheel dust cover and watch while cranking,
Does the starter pinion gear engage but not turn the flywheel when you hear the loud click?
With the truck running is the flywheel centered or is the ring gear wobbling?
The things that your trans rebuilder touched are all right there,
Did he bend or mar the gears on the flywheel?
He may not have seated the converter fully and its bound against the trans front pump, they don't usually last very long when this happens.
Its not uncommon for a meter to be off a couple volts, not detrimental but now we know your close to the norm as far as voltage goes.

Things to check with the dust cover off,

Neal

 

Did you check both sides of the solenoid for voltage?

 

Ok, I will perform those tests next. Scary that you brought up seating the converter fully and that breaking the pump....... because this guy had to do it multiple times to get it right. 6 days after getting the Hummer back the FIRST time from him, the trans went out again and it was the pump........and he says "I have never had a pump break in all my years type of comment". And he had never done a Hummer trans before. I tried to tell him they are slightly unique with the 5 planetary gears instead of 4 (atleast that's what I think it is from memory last year) AND that they have a 1mm different torque converter......to make sure he didn't get the wrong one. (He got a "rebuilt" converter). But he was full of pride and rude, and couldn't be told anything.......

Before I get into all that checking the flywheel ect, which means removing the starter again, can we make sure the 10 10.5 volts going to the purple solenoid wire isn't the problem? Wanted to make sure you understood the one message about with adjusting the readings from my meter being 1.5-2 volts off........I'm actually getting 10 - 10.5 volts at the solenoid wire. (Not around 12 volts like I originally thought). I'm reading online, that, that is enough to cause starting issues. Thoughts?

 

I feel ignorant here, but not sure what you mean or how to. I just check the voltage at the s stud itself. The tiny stud where the purple solenoid wire connects.

I'm used to

"s stud" for the purple (solenoid) wire
"Main stud" for the constant hot wire directly from battery
And I don't know what to call or what it is, for the other large stud that I believe connects the starter and solenoid?

 

Thank you Bronx. After what I learned in the last 24 hours (with purple wire voltage being low) I'm wondering the same thing. Any tips on how to "carefully" open up and test the ignition switch? Or maybe a link to a "Hummer how to"? Electric issues and being careful can be my krptonite lol

I'm learning a lot though, so atleast there's that.

 

The wire leaving the solenoid going to the starter motor,

GM says 10 volts is minimum while starting, any lower you'll usually get loss of communication messages form the modules on the truck (U-Codes with SES light)

Neal