3.6L Manual - Won't start after sitting, starts consistently after a jump - JeepForum.com
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post #1 of 5 Old 07-14-2021, 11:30 AM Thread Starter
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3.6L Manual - Won't start after sitting, starts consistently after a jump

So, I've got a 2012, 3.6L Manual. One day, it just wouldn't start. I got the standard "click-click-click". I jumped it and drove around a bit, then stopped by an O'reillys to have them test the battery, alternator and starter. Everything passed, so I figured that maybe I just had left something on or had a short somewhere.
Next day, i had the same problem. Jumped it, then ran some errands. At every stop (about 5), it started up immediately. I went to a different O'reillys, had them check everything again and it all passed.
I cleaned the battery terminals and replaced my felt pads (the negative pad had pretty much disintegrated) and went hope and started testing for parasitic battery draw. Hooked up my multimeter and after letting it sit about 10 min, I was at about 10 milliamps, so I didn't bother doing any fuse pulling.
Before heading to bed, I checked the voltage at my battery and was at about 12.75v. Checked it this morning, and it was at about 12.3v and _again_ it wouldn't crank. I jumped it, drove 5 min to the grocery store, hopped back in and it turned right over.
I am stumped, and it's 112 degrees outside, so I'm just getting tired chasing electrical gremlims. I was going to check voltage drop between battery and starter next, but does that make sense since it starts up every time after the initial jump start? Anybody have any ideas of what I need to check?

EDIT: It just started up just fine after sitting for about 5 hours, so I have NO idea what the threshold might be.

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post #2 of 5 Old 07-15-2021, 10:34 AM
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Run a second engine ground, many do it from battery negative to alternater bracket with a 4 gauge wire. Cheap insurance for the crappy Jeep ground wires. If that does not do it then how old is your battery, if it is the original then I would replace it no matter what O'Reillys says.

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post #3 of 5 Old 07-15-2021, 03:16 PM
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^^^^^^ What he said.

If it's the original, stock battery, it's time to replace it.

How long does your Jeep normally sit? You might consider a battery tender for it if it's weeks at a time.

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post #4 of 5 Old 07-15-2021, 03:36 PM
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You check that voltage at start if it falls below 12v under load of starting the battery is not good even if it shows 12.5 static. should not be lower then that static anyway. But load is what you are looking for.

stock battery and its a 12? no way. if it is should have been replaced long ago. My 12 built in Aug of 2011 is on number three and it is at that point of i may just replace soon anyway. I live in Havasu so its hotter here and it dont play well with battery life, cooling systems.

One thing before grounds but related is you have not used the battery cables nut to say be a hot or ground? Its a 10m nut and it is tapered so when it goes tight it tightens the post. If you say run anything from that post it wont seat with a electrical wire there. This has happened more then a few times when people add a winch, lights or amp. Its convenient, but cause battery issue when that cables not tight as it should be.
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post #5 of 5 Old 07-15-2021, 06:24 PM
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battery 4years and it time to replace - how old is this battery?

You did not mention - how long a rest - hours, days, weeks? Or did I not see that...
Tell us what changes, modifications or additional electrical components?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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