Hard starting after sitting overnight

[norville]

I'm sure this isn't new but I've been going crazy looking though googles trying to find the exact issue.

Our 2020 wrangler 3.6 auto has developed a hard start issue in the morning. It will crank a few times and try to start but immediately stall. Then on the second attempt is a bit slower crank , labored crank but fires up.

Dash is reading 14.1 v , no error codes. I did not hook up jscan yet to check any hidden codes.


My first thought was battery issue but it doesnt seem to be the case. Next was fuel, I changed out the fuel pump relay and I'll check it tomorrow. Fuel filter? Or could it be the fuel pump check valve?

Any other thoughts? Anyone have this issue?

Thanks
Bob

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[mwilk012]

The engine light on? Sounds like a fuel or crank sensor fault.

Wait a minute, only one failed start attempt and it’s cranking slow? How weak are your batteries?

 

[norville]

I did a quick measurement across the main battery posts. It's reading 12.23v. I also checked my gladiator and it's reading 12.37v.

After swapping out the fuel pump relay last night I had no issue with starting this AM. I will keep an eye on it, I'm not 100% sure that was it.

Even though it did start , it's not as strong of a crank as my 2020 gladiator has in the morning. It could be something as simple as cleaning the battery posts. my imagination or maybe I should pull fuse 42 and isolate the sad cable from AUX battery before something bad happens.

Both jeeps have approx 50k miles and original batteries.

 

[jludave]

Both jeeps have approx 50k miles and original batteries.

Time to change batteries. You have a 2020 and are beyond what is considered the useable lifespan of the OEM batteries. Change both the main and aux, or change the main and bypass the aux.

 

[OBD]

I would bypass the auxiliary battery and check the main under a load.I suspect the main will show it is weak.If so, I would leave the auxiliary bypass and replace the main with the larger battery.I don't believe it is recommended to continue to use the start stop feature if you go this route.

 

[norville]

We never use the start stop

 

[mwilk012]

Don’t care, they’re dead. Your gladiator is right behind. 12.2 is dead. The fuel pump relay is fine.

 

[Terrymo]

Google 12 volt AGM battery voltage chart. Manufacturers vary slightly on state of charge percentages but here is one example

 

[norville]

I feel a bit dumb, I didn't realize these are AGM batteries.

 

[Terrymo]

Those voltages are considered low for any automotive battery.

 

[norville]

Thanks all, ill grab a new battery for the wrangler today and next month one for the gladiator. $250 a pop. I'll also bypass the aux batterycwhile I'm at it on both.

 

[Rhinebeck01]

Thanks all, ill grab a new battery for the wrangler today and next month one for the gladiator. $250 a pop. I'll also bypass the aux batterycwhile I'm at it on both.

Be sure to go with H7 AGM in regard to both the JL and JT.

Read here:
https://www.jlwranglerforums.com/forum/threads/??-main-battery-replacement-talk-jl-jt-?.100534/

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