94 4.0 auto won't start without a jump

[WhiteDevil1311]

I don't drive my XJ much anymore, every issue I fix 5 more sprout up. I do start it once a week and take it out on the road for about an hour.
3 weeks ago ran just fine, shut off and go into a store, 15 minutes later it won't start again. Let it sit for 30 more minutes and started right up but lost my brake lights?
Since then I've driven it 4x and no issues, today I went to start it for her weekly ride and it just cranked and clicked (low voltage) so I used my wife's cars with a brand new battery that tests at 12.8v to jump the XJ, took 30 minutes to let it get some juice and nothing, another 30 minutes and it started.
Let it run for an hour to get nice and warm, took it around the block with no issues. I parked it, killed it and let it sit for about 1 minute, started it again and no juice....
When it was running it was between 12 and 14 on the voltmeter, fuel system is working, have spark....
Any pointers would be great. I plan on removing alternator for a bench test probably Friday.
Thanks in advance.

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[4.3LXJ]

That is where I would start.

[WhiteDevil1311]

I figured that but it's a jeep

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[Mudderoy]

Not that it would fix this issue, but you might want to put a battery disconnect on it.

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[MattybPDX]

Bad battery?

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[WhiteDevil1311]

Bad battery?

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Getting 11.8v

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[MattybPDX]

Terminals clean?

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[WhiteDevil1311]

Yep. I'm going to start with the alternator.

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[Charlie Foxtrot]

Just curious, did you solve your issue?

[WhiteDevil1311]

Yes actually fixed it today finally, dead battery cell, simple fix but had a work van to use so I let it sit until today.

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[WhiteDevil1311]

Simple fix lasted a day, cam sensor and temp sensor both quit on me today. Fixed the current issue, I'm sure there will be more but cam sensor only had 1200 miles on it.

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[Charlie Foxtrot]

Just a thought - when you get it running, check your voltage across the battery while the engine running (or keep an eye on the voltmeter on the dash). Watch for voltage spikes greater than 15v. Sometimes a wonky voltage regulator (it's in the puter - post Renix jeeps) can allow transient voltage spikes. Sensors (& computers) don't like transients, and show their displeasure by failing when you need them the most, or have empty pockets. Voltage spikes can eventually kill a good battery. Kills bulbs, relays, flashers, radios also. Examine the harness from the alternator (this info is for Mopar alternator, typically ND, Denso or Bosch). Look for wear spots on the wires. The regulator excites the alternator by a signal to ground (the blue or the green wire, don't remember which). If the conductor (copper part of the wire) makes contact with ground, you can have a runaway alternator (voltage spike). The bulbs get brighter, and if it goes on long enough, you start frying things (expensive things). Renix alternator/voltage regulator system can fail also. Same symptoms, same effect, slightly different cause & fix. Good luck.

[WhiteDevil1311]

Ended up being the cam sensor that was replaced 15 more than ago. Sorry I didn't get a notification of a reply.
Currently it's down, zero brake pedal. Seems the rear end has no brakes and axle seals are toast.
Pandoras box man.

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[WhiteDevil1311]

Have brakes again. Ordered up an oem spec rear drum kit from rockauto to do the backs (drums,shoes,all hardware and wheel cylinders for 90 bucks).

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