You have some great advice here. Those grounds need cleaning. If your Alt. ground is that bad I'm sure the shock tower/chassis one isn't any better. Your terminals look good but make sure they have zero movement when tight. My '01 had different OEM terminals. No matter how much I tightened them the positive could move a little and the ground could pop off. The big question is if you have been driving without the body ground attached? Picture two shows it laying on top of the battery plate as pointed out. That could explain why you had M+S pop up while traveling. Secure that to the ground bar tab. Someone can correct me but if that isn't attached correctly then your battery isn't grounded?? It's been 12+ yrs since I upgraded the Big 3 so my setup is different. Finally, it doesn't matter how new your battery is. Get it checked and charged up because those numbers are no good. I had a thread from couple years ago "Battery Options". I went through several Irish Big Box AGM batteries. I'm no fan. Currently running a X2 Power Battery Group 34/78 from Batteries Plus. 4yr replacement warranty. Hopefully, you just need a battery charge up. Clean ALL the connections and attach the ground tab.

 

I want to make sure I am aligned with the voltages:

No load/Key off: 12.1 (50%) - 12.5 (80%). Assuming the 12.5 was across the posts, so battery is either not fully charged or not fully healthy.
Key at "run/ignition": ??? You said it was at 11.5v, but since you also said you needed a helper I am gonna assume you meant the 11.5 was with the key in the "start" position
Start/Crank: 11.5, but with no noise. In theory the voltage could be much lower during cranking. But, I think what this actually indicates is that the starter can't draw fully from the battery.

12.5v with everything off is not great, but should be plenty to make the solenoid close and the starter spin. 11.5 while the engine is actually cranking is pretty solid...but your engine never actually cranks. This suggests to me that somewhere you have a bad path either to the battery or from the battery.

Edit to add: The "bad path" could be inside the starter or solenoid windings themselves.

 

Good afternoon all, sorry for the radio silence. The last few replies did not send me a notification for some reason. But to confirm @H20nSnow 's guess, no, between the rain that's been stalled over Central Florida, and traveling to see in-laws over the weekend (would have much rather been wrenching), I had not gotten around to working on the Disco again...until today.

1. I did manage to pull the ground cable out a few days ago and cleaned it up along with the bolt
2. Today, I took my drill and wire brush and cleaned up the surface where the ground cable attaches to the alternator bracket
3. I also cleaned up the battery terminals, a 5 second job since they were already quite clean
4. I also got underneath her and double checked the tightness of the positive wire to the starter and the solenoid. I was able to give it a good quarter turn, but otherwise all was snug

Once I reconnected the battery, I hopped in the driver's seat and was getting a much louder *CLICK* but the starter still wasn't engaging. Weird right? Well we all must be on the same page because without realizing how much help I was getting in this thread, I went ahead and yanked the battery out and drove it to my LPS.

The worker was surprised I wanted a test since the battery isn't even a year old - 11/23 - but lo and behold, a discharged batter. It read 1/4 of the cold cranking amps it was supposed to output (200 tested vs. the 800 @ 0º and 1000 at 32º) hence the *CLICK* with no starter engagement.

The batter is sitting down the street on their tester as I type this. They said to come back in an hour if I don't get a phone call. So fingers crossed she fires up once I go back for the battery after my last work meeting ends for the day.


BODY GROUND
I have been wondering how necessary that tab is. This is my first Disco and when I bought it that's how the body ground tab was. Just loosely placed on that bracket. But the truck has been starting and driving without issue since I acquired her, so I didn't think it was entirely necessary to tighten down. I have a box of nuts & bolts somewhere so I'm sure I can find a couple that will hold onto the tab tightly based on what @Richard Gallant , @JohnZo , and @Windycity_rover have pointed out.

Next update to come soon!

 

You nailed it @sqlbullet - I'm hoping the "bad path" is a combination of the body ground tab and the discharged battery

 

There's good news and there's bad new

The good news is, batter recharged fine. Retested and it's putting out 13V, 770 cold crank amps compared to the advertised 800

The bad news is, the charged battery did nothing.

• The first couple turns of the key I heard a few loud *CLICK*s
• And then, the last few attempts I made before coming back inside I wasn't even getting a click.
• I figured if it indeed was the alternator, as @H20nSnow suggested, I at least would have been able to get it started off battery power and move it back into the garage.

But fully charged battery and still no start? Where am I going wrong?

 

Bad starter solenoid? Have you bypassed it yet?

 

@H20nSnow , some assistance based on the photo below? Additionally, this is a new starter and it did work for several test starts and a couple of test drives. Would the solenoid go badly that quickly?


What exactly am I supposed to be jumping between to test activating the solenoid?

 

Place a large screwdriver between those two lugs on the start and see if it turns. It is possible with the low battery you arced enough on the solenoid contact ring to pit/burn it and now it won't start. Did you try jumping the relay?

 

To expand on Extinct’s comment, jumping those two large studs bypasses the solenoid. If it works then the solenoid is bad. If it still doesn’t work then you still have a cable or battery problem. If it works then move up to the start relay that drives the solenoid. If it works there then you have a bad relay. Keep moving up the chain until you locate the device that works when you bypass. That is your failed device. Make sure you don’t get hung up trying understanding why a given part might be bad before testing it. Test it THEN understand why it’s bad, or move on if it’s not.

 

I don’t remember, did you ever try jumping from a know good battery? I’m still suspicious of your battery. Unless they did a load test, a battery that reads full voltage still might not have enough capacity to turn your starter.