i have been thru this, it ended up being a bad negitave battery cable for me. when you have this problem and take off a cable then reinstall it, and its working fine after that then its that cable. next time it happens, pop the hood and try and start it, if there you see a lil bit of smoke come off a wire then that is the point of a bad connection, could be as simple as maybe needing a new cable end

 

Yes, that is correct on the DMM. Looks like your battery is good to me. If it had gone down to 9 or less, I would have told you it was the battery but, in this case, it's looking more like a starter issue.

I had never heard of the bad cable as was posted below. Good thing I read that one as I would have never thought of that. I will add that one to my list.

 

one thing to remember about cold starts is that number on the battery that says cca###. if it is not a bad (sticking) starter then it could be low cold cranking amps. my oem battery had 600 cca and i replaced it with an everstart maxx from walmart. the new one has 875 cca and 1000 cranking amps so now it really zings the starter compared to the slow lope that it had before.

 

at 10.4 volts under load - your battery is dead.
replace it.

here's a good technical explanation of why the truck runs like crap with a weak battery.
https://dodgeforum.com/forum/1825794-post7.html

here's another, but its hard to read for all the bickering going on.
https://dodgeforum.com/forum/1st-gen...questions.html

 

No kidding DH. Interesting. I thought it was <10 VDC and below that constituted a dead battery. Oh, well, you learn something new everyday.

EDIT: just read that post: most of that is bogus information right down to the simple terms as to what an alternator is to how it works in the system. Lots of misleading information there.

 

well, yes/no/maybe. some of its just interpretation. i try to keep and open mind and maybe learn something.

either way, its common among the ram, dak, and durango sections for everyone to complain the truck runs like crap with a weak battery. my simplified conclusion to all this is still, that for whatever elec engineering reasons, it screws up the signals that the sensors and pcm use to communicate with each other. the result is something's not quite right with fuel mix or timing, since compression and spark are fixed events. and like everybody says - the truck runs like crap and won't idle.

on all the old vehicles i every had, if you could get the SOB started, then you could usually remove the battery and just run it off the alternator. something about the computers just doesn't allow that on our trucks. not worth worrying about. just accept it and install a good battery.

 

I have to disagree with this. I just went out and tested my other car using the same method and the battery on this one dropped to 10.2v when cranking.

Try it on your truck sometime.....

 

Yeah, that's what I found when I tested mine too and the car as well. No battery or, no power supply for that matter is going to supply full voltage under full current draw. Whether it's a DC hand drill running at 18 VDC to your car battery- there's going to be an initial voltage drop. Then there's a recovery time after the start at which point, the current draw reduces and the battery voltage recovers and levels back out.

The trick is how fast it recovers and, if the time is too long to recover after the initial draw down, then we can say the battery is weak and needs to be replaced soon. My ladies car does the same thing as we just tested that out this morning after I read that post. Her battery also draws down close to 2 volts upon hitting the starter so, based on what I have seen with two vehicles and one poster here reporting the same results, I am in doubt over 10.4 VDC constituting a dead battery.

 

The real question is: what is the voltage range on the PCM / system. There has to be a tolerance. Is it 12 VDC ± 1 volt, which would be 11 - 13 VDC input or, how about 2 volts which would be 10 - 14, etc, there has to be a range and, I for one would like to know what that is.

Since the general consensus is that every Dodge runs like crap when the battery is low, I for one would like to know just what the voltage range is. I would also like to conduct some tests with measurements at varying parts of the circuit to see what difference in voltage input and output and to what extent it affects those.

The thing that does not make any sense (at the moment) is that the alternator is outputting a charge of ~14 VDC to the battery in order to charge it. Without knowing the circuit in it's entirety, the Alt voltage should provide more than enough power to overcome a low battery condition and provide adequate power for the entire system to run on. Perhaps it's not clean enough or has lots of noise and is not intended / designed to do anything more than simply charge the battery. If that's the case, that explains a lot.

However, without looking at the circuit in it's entirety nor doing any tests to prove this to be true or false, I am not certain on the above statements.

When I get some time, I would like to test this and measure the results. I know poor grounding will throw off voltage to all the sensors in the vehicle and the PCM as well right to the EFI system too so, you never know.

Anway, good information to ponder over nonetheless.

 

ok, i might be wrong. i got results similar to you. here's what i did.

after letting the truck sit for a couple of hours, put the multimeter probes in the slots of the battery terminal, and prop the meter up near the windshield. initial reading is 12.3
disconnect coil. turn and hold the ignition and let the starter spin and watch the meter. its reading 10.7 - 10.6
repeat this a couple of times. results were the same.
release the ignition and check the meter. it returns to 12.3
reconnect coil and start the truck. meter is reading 13.5
idle is perfect.
shut off ignition. meter reading 13.2 and slowly dropping. 13.1, 13, 12.9....