Changed batteries, now continual cranking. No start

[TroyChurch]

2018 Wrangler JL was getting a bit sluggish in starting. Wife got to work - Jeep dead, but with power. Had changed out auxiliary in November. Had main battery replaced. All systems GO including alternator test. Starts right up. She gets 10 blocks from work and “find safe place - vehicle shutting down”. She pulls over and then nothing. Completely dead. Towed home. Main battery (new) tests fine after pulling it out. Has full charge and tests great under load. Dig out the 9 month old auxiliary battery and it’s very low. Take it in and get it tested - BAD. Only a THREE MONTH WARRANTY! Buy new one and install. Put everything back together…
Now… The Jeep cranks like it has a battalion of hamsters running in a wheel, but it WILL NOT START.
HELP! What hair I have left that hasn’t turned grey is turning loose!

Troy

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[oldcjguy]

check the fuel pump fuse. See if it popped during the battery swap. Also, not surprised the aux battery went bad. Main and aux are tied together so when one starts going bad it brings the other down with it.

 

[TroyChurch]

Fuses checked. Relays swapped out and introduced a new one. Batteries have been on trickle charge for more than 24 hours. I cannot hear the fuel pump, but since we have had this jeep for almost a year, I have never recalled hearing the fuel pump. so, I am not sure if the fuel pump is even engaging, given the strange set of circumstances. I am stumped!

 

[Reinen]

2018 Wrangler JL was getting a bit sluggish in starting. Wife got to work - Jeep dead, but with power. Had changed out auxiliary in November. Had main battery replaced. All systems GO including alternator test. Starts right up. She gets 10 blocks from work and “find safe place - vehicle shutting down”. She pulls over and then nothing. Completely dead. Towed home. Main battery (new) tests fine after pulling it out. Has full charge and tests great under load. Dig out the 9 month old auxiliary battery and it’s very low. Take it in and get it tested - BAD. Only a THREE MONTH WARRANTY! Buy new one and install. Put everything back together…
Now… The Jeep cranks like it has a battalion of hamsters running in a wheel, but it WILL NOT START.
HELP! What hair I have left that hasn’t turned grey is turning loose!

Troy

The Aux battery not lasting is completely expected when the Main isn't replaced as well. Main & Aux are linked 99.99% of the time. When you link a new battery with an old battery, the new battery gets destroyed very quickly.

Replace both Main and Aux at the same time. Having both batteries the same age & use is very important to longevity.

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