2021 Struggling to start

[GetGlad]

On Saturday, my jeep started having issues starting. It happened the first time after a trip to the hardware store to get my original bumper off, and I had just disconnected the fog lamp harness. It usually happens when the engine is cold, but has done it after a short drive as well. Itll turn over but not start a couple times, then start, and have no issues running after that. Once its warm, it usually has no issues starting. I went to Oreilly and had them run checks (batt, alternator, starter) and all passed, but the battery is over 3 years old with 38k miles (original battery). I just retested after sitting a few hours, and the multimeter showed 12.2v. I replaced the Aux batt a few months ago, but not the main battery. Sometimes when it does successfully start, the red circular light under the speedometer is on. My driver side running light is also intermittently on. These two make me think its electrical, but I'm concerned its the fuel pump. I'm planning on replacing the main battery this weekend. Any thoughts?

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[NOTJeepBeerSleep]

walmart has a good battery. mine did the same a couple months ago 21 also

 

[Lost1wing]

12.2v is not good for an AGM. You can try an AGM charger on both batteries, independently of course. Let them sit isolated for a while and read the voltage again. 12.8v would be great to see, but 12.6v for the age of main wouldn't be unusual.

If you just want to start with replacing the main, you kind of have to do the same. Charge both batteries independently before installing.

 

[Lost1wing]

On Saturday, my jeep started having issues starting. It happened the first time after a trip to the hardware store to get my original bumper off, and I had just disconnected the fog lamp harness. It usually happens when the engine is cold, but has done it after a short drive as well. Itll turn over but not start a couple times, then start, and have no issues running after that. Once its warm, it usually has no issues starting. I went to Oreilly and had them run checks (batt, alternator, starter) and all passed, but the battery is over 3 years old with 38k miles (original battery). I just retested after sitting a few hours, and the multimeter showed 12.2v. I replaced the Aux batt a few months ago, but not the main battery. Sometimes when it does successfully start, the red circular light under the speedometer is on. My driver side running light is also intermittently on. These two make me think its electrical, but I'm concerned its the fuel pump. I'm planning on replacing the main battery this weekend. Any thoughts?

When you say turn over, does that mean normal turn over speed? Or is it sluggish, not full speed?

 

[GetGlad]

When you say turn over, does that mean normal turn over speed? Or is it sluggish, not full speed?

The engine tries to start, but doesn't. Its not the typical clicking you hear with a dead battery. It sounds like its going to start, but doesn't

 

[Lost1wing]

This is when a scan tool comes in handy. You could verify fuel pressure and scan for codes and pending codes.

 

[Texbaz]

Maybe, you could measure the batt voltage during start. If its dropping to say 10-9 volts it has enough to rotate the engine but not enough to keep all the other electronics active.
Yes, 12.2 is not good for an AGM, might want to do a charge cycle. or put a battery jump cables on it and try a start basically giving your batteries an assist.

 

[ecidiego]

I've been hooking my AGM charger up through the trailer 7 pin once a month to maintain my batteries. The alternator will never completely charge them regardless of how long a road trip is as it cuts off below the necessary float voltage for AGM.

 

[Texbaz]

I've been hooking my AGM charger up through the trailer 7 pin once a month to maintain my batteries. The alternator will never completely charge them regardless of how long a road trip is as it cuts off below the necessary float voltage for AGM.

Well, I would still measure voltage drop during start. But, if you can't get the battery charged up to what a AGM battery should be then I would think you have a battery problem.

Have you measured battery volts with the truck running what are they I would think the alternator would be putting at least 13.5-14.1 volts if your battery is that low (12.2).

 

[DailyMoparGuy]

Like others said, 12.2 V is way too low. 3 years sounds about right for it to be bad

Hook it up to a charger over night. The voltage should be 12.6V or higher after charging (depends on the manufacturer and battery type I believe). Note whatever the voltage is right after you unplug it, let it sit for 6 hours or so, then check the voltage again. If it drops below 12.6 then it’s probably bad.

Also, I did all those steps above for mine AFTER removing it from the truck. My battery issue was more cut dry - the voltage dropped below 12.0V after 30 minutes lol

 

[GetGlad]

I checked it again after a few hours and it had dropped to 11.9v. I think I have my answer.

 

[Lost1wing]

My batteries are now 5 years old. Last week I checked my voltage after 2 weeks of sitting. I was at 12.1vdc. Before I even attempted to start it, I plugged in the NOCO for an over night charge. After forgetting that I plugged it in, I unplugged it two days later. I got distracted going to get my meter, so I didn't test it until the following day. It was at 12.6v. Two days later, 34f outside it started normally like normal. 5 minutes later my Stop Start was ready.

Had my initial voltage reading been any lower, I would have been looking at new batteries. I will see how long they can last.

 

[Mister Lamb]

Just change the batteries and save yourself the headache for the next 3 years

 

[Deleted member 52902]

Buy and install BOTH batteries in your JEEP at the same time. Before you install them, as a complimentary pair, please put them on a trickle charger. Ideally a low amperage charger/maintainer overnight. Or whenever the charger indicates it has completed the charge and an indicator says that it is now in in maintain-mode. But you can leave these running without percolating the battery uncessesarily when they automatically switch into maintenance mode.

Do not expect that the batteries are at full charge when you buy them. They typically won't be although we might assume they will have a full, or close enough to full charge. Best not to guess. You may start out with an issue that might not go away which will affect the batteries total longevity. Even more so with two batteries that are also of different size and capabilities. Like cold Cranking Amps, and Reserve Time to provide high current output.

Get both, charge both into their maintain mode. You will likely have only one of these maintainers so I would start with the wee little Auxiliary battery first. It can flip a charger into Maintenance mode, sooner in most situations, then do the large capacity capacitor (large battery) afterwards. Both of these now at their peak within the hour(s) or single day you do this, now install them.

Would a shop that sells and installs batteries do this? No. They need to sell, install and move on. the batteries may have drained off a bit during the weeks and months in some cases, these sit until sold. Your battery life can be improved if they first time they get hit with a load, that they are working from their maximum ability. With subsequent charge-use-charge-use cycles better able to function for longer life.

Some of the battery life can be compromised with goofs we might make along the way. Like a device wired in that does not get switched off when we park the vehicle of hours or overnight. If not also on the ignition switch to cut these devices off, some might draw enough current to make a dead battery that requires a jump start. it happens. But avoiding these where the battery might have been totally or nearly totally drained down - makes a difference vs a battery treated more kindly.

Back to the beginning paragraph; do yourself a favor even though the pocketbook suffers an all at once hit; Replace both of them at the same time. And if time allows, give both of them some juice to make sure they are truly at full power, ideally accomplished with say, a 1 or 2 amber charger/maintainer that automatically adjusts its output to match lead acid or AGM batteries that your going to install.

 

[Sbro2021]

I just replaced my batteries yesterday at 3 years and 2 weeks old. Started with the remote start not cranking because voltage was too low. Then continued to get worse and before I knew it, Jscan showed me that the charge % was down to 17% and over an hour highway drive commute for work, could not get the alternator to get it north of 22% with 14.5V tryin hard to. Auto parts store told me the battery was fine, and I mistakingly listened to them and drove it one more day, Jumping it multiple times over the course of 10 hours. Just replace them and do BOTH! Yeah it's 400$.... At least for an AGM 94R and the 48 dwarf battery that never gets used anyway, at least on mine.. S/S has never really worked since day one off my rig.. and do the 94R, it's 850CA versus the 650 of the OG unit, biggest one that will fit in there anyway. all issues gone, battery % back up to the top as it should be.

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