Ok, so here's the possible problem: Bad ECU

Here is the current setup:

92 XJ Limited
168k
117 amp alternator
2ga wiring for power and grounds (fused link w/ voltmeter between battery and alt)
Battery - brand new, fully charged and tested.

Here is what happens and the tests:

First start up is hard, if it turns over at all.
If it turns over, the dash voltmeter shoots to near 14. The voltmeter shows 14.4 and the multimeter shows 13.25 at the battery.
With each start, it will go down on the dash. Sometimes a little, sometimes a lot.
Today I checked the voltmeter, and it read 14.0 a couple different times, rather than the 14.4 or 14.5 I get when I've checked it other times.
After 4 to 6 hours it can be dead. Usually a night is verboten (especially after this morning).

I am going to work the grounds on the interior tomorrow, to see if I can affect the electrical issue.

Am I in the right spot, or am I missing something.

 

how old is the Alternator?

what does the dash say if you try disconnecting the alternator (either unplug it or remove the drive belt which ever is easier for testing) and cranking.

Also does the battery go dead overnight with the alternator unplugged. and alternately try pulling the fuse for the the ECM overnight and see if that helps.

I'm not exactly clear on what the hard start issue is exactly there are a couple of different variations? is it a slow crank? is a strong crank with the car trying to fire? do you hear a click sometimes and a crank others?

Try disconnecting the battery for 60 seconds and reconnecting to see if that helps "reset" the system.
Given the age of the Jeep it could be an ECM but more testing should be done first.

 

Search for a draw.

 

Draw - tests were done with no draws.
Alternator - brand new.

Battery ended up going bad.
Napa Legend 58 class flunked it's load test this morning after dying on me again 3 hours after running.

Going to pick up a 34/78 battery for emergency vehicles (800 cca) from Napa and see if it'll help out. On Monday or Tuesday.

Figure if I see any issues after that I'll know where to go. Unless this battery's crap too.

 

That and I plan on pulling the ecm to see if any cleaning is required or anything looks unpleasant.

 

Other than the connector, there's nothing to see on the ECM.

 

I've got a 65 series battery in mine
Fits right more than enough juice

 

I went and snagged a 775 cca napa agm batter (group 34).
Fits perfectly, same problem though.

Starts nice, dash meter jumps to near 14. Each successive start it drops.
At this point it's grounds or ecm.

I'll look into it here in a bit, right now I want to work on taping up the interior and getting all the plastic bits off to paint while I sand and primer the interior back for Herculining.

 

So I need a list of all grounds and their locations.

 

If there isn't a sufficient ground wire going from the alternator to the engine block, in comparison to the power wire running from the alternator to the fuse to the battery, would it cause charging issues?

 

Here is my current engine wiring setup:

2 ga wire all around.

Grounds:
Alt to battery
block to battery
fender to battery
back strap

Power:
Alternator to 150 amp fuse block to battery.
Battery to pdc (fuse pulled for alternator)

 

It's not uncommon for engine grounds to fail. Try unplugging the alternator. I have seen alternators cause a draw. Also 8f you haven't replaced the battery terminals I would. Even if they look ok jeep terminals are notorious for failing internally. What was your amp draw reading?