Starting question

[ChrisS53165]

Hi - I have a 2018 Ram Big Horn 5.7 liter V8. Recently, I have had random issues with starting. I put a new battery in last year. Yesterday it was dead. Jumped it and it started immediately and ran just fine. Went on about a 20 mile drive then stopped for gas. It would not start again. Jumped it and it ran perfectly till I got home About 30 minutes later.

Here is what I tried:
Turned the headlights on and checked battery voltage while running…14.8v
Shut the truck off and checked battery voltage…12.8v
Tried to start and needed a jump
Started it, removed the positive battery connection and immediately it died, no headlights on
Hooked it back up, tried to start it up and the damn thing started. Yes, everything was tight prior.
Tried starting several times throughout the day and had no problems

Any idea what would caused this? All of this seems random….where do I start looking?
Thanks in advance

 

[RamDiver]

This starting problem is most likely that your new'ish battery is dead.
And, the new battery has died a quick death due to a mystery current.

Our trucks have so many electronics that sometimes a module doesn't enter the sleep state and then sucks the life out of the battery.

The first thing is to get a trickle charger on the battery ASAP.
Leave the trickle charger connected whenever the engine is off.
Then, load test the battery with a toaster-style load tester like the $18 device from Harbour Freight.

100 Amp, 6/12V Battery Load Tester

Amazing deals on this 100 Amp 6/12V Battery Load Tester at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

I hope you own a jump pack; if not, now is the time to get one.

There are many threads on the subject of isolating mystery currents.
The job is technically not very difficult, but it can be a bit tedious.

I prefer to use a clamp meter first to determine the amount of load we're searching for.
Then, a digital multimeter is used to measure the voltage drops on the fuses, and a look-up chart to determine the current flow.

I will find the chart and post ASAP.


And, welcome to Ram Forum.

.

 

[ChrisS53165]

This starting problem is most likely that your new'ish battery is dead.
And, the new battery has died a quick death due to a mystery current.

Our trucks have so many electronics that sometimes a module doesn't enter the sleep state and then sucks the life out of the battery.

The first thing is to get a trickle charger on the battery ASAP.
Leave the trickle charger connected whenever the engine is off.
Then, load test the battery with a toaster-style load tester like the $18 device from Harbour Freight.

100 Amp, 6/12V Battery Load Tester

Amazing deals on this 100 Amp 6/12V Battery Load Tester at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

I hope you own a jump pack; if not, now is the time to get one.

There are many threads on the subject of isolating mystery currents.
The job is technically not very difficult, but it can be a bit tedious.

I prefer to use a clamp meter first to determine the amount of load we're searching for.
Then, a digital multimeter is used to measure the voltage drops on the fuses, and a look-up chart to determine the current flow.

I will find the chart and post ASAP.


And, welcome to Ram Forum.

.

Thanks for the quick reply. Just went out and checked it after sitting all night. No go. Gonna have it load tested. I’ll report my findings

 

[ChrisS53165]

A VOM check and it’s still 12.2v. Load test is the next check

 

[RamDiver]

A VOM check and it’s still 12.2v. Load test is the next check

Yup, it's likely toast.

As mentioned, get a trickle charger on the battery ASAP, until you find the electrical gremlins.

FYI, the digital load testers used at parts stores are very prone to false positives.
They're junk, AFAIC.

.

 

[turkeybird56]

A VOM check and it’s still 12.2v. Load test is the next check

Battery.....

 

[RamDiver]

How much experience do you have with electrical and or electronics?

I prefer to start with an amprobe-type meter to determine how large of a current is causing the grief. This will also allow us to rule out the smaller fuse values potentially.

The fuses in the TIPM (fuse box) have tiny test points allowing us to use a multimeter to measure the voltage drops. Then, with the attached voltage drop chart, we can determine the actual current draw on the circuit.

.

 

[Rado]

I am no help but following !
Is everything dead when you try to start ?
Any clicking sounds ?
So really curious on what you find out

 

[mtnrider]

Bad battery, get it load tested. Measuring the voltage is not a good indicator of battery health


.

 

[ChrisS53165]

Ok, had it load tested…800 CCA shows 805. Alternator checked out fine. Starter checked out fine.

Now that the truck is warm, it starts with no issue. Gonna let it sit for an hour and see what happens.

I did have the stereo head unit changed out by CDJR over the summer but have not had any issues until yesterday morning.

I have no clue at this point

 

[crash68]

Tried to start and needed a jump
Started it, removed the positive battery connection and immediately it died, no headlights on

If I'm reading this as you disconnect the positive battery connection from the trucks battery while it's running, don't do this. Removing a battery terminal while the engine is running to see if the alternator will provide power to run a modern vehicles is a good way to blow out control modules. Even if the battery is half dead it will still buffer voltage spikes.

From a safety standpoint when dealing with automovive batteries, it is always negative on last and off first. Doesn't matter if it's the vehicle battery cables or jumper cables.

 

[RamDiver]

If I'm reading this as you disconnect the positive battery connection from the trucks battery while it's running, don't do this. Removing a battery terminal while the engine is running to see if the alternator will provide power to run a modern vehicles is a good way to blow out control modules. Even if the battery is half dead it will still buffer voltage spikes.

From a safety standpoint when dealing with automovive batteries, it is always negative on last and off first. Doesn't matter if it's the vehicle battery cables or jumper cables.

I completely missed that detail about removing the positive battery terminal. LOL
My brain must have filtered that out. So much for multi-tasking.

.

 

[turkeybird56]

I completely missed that detail about removing the positive battery terminal. LOL
My brain must have filtered that out. So much for multi-tasking.

.

THAT's an old GM trick, where PPL would pull the "NEGATIVE" (not positive) cable, and if vehicle still ran the general consensus was the alternator was still good. This goes back to the old black box voltage regulators mounted on the firewall.

OP, definitely heed to post #11. Horrible idea to pull cables on a rolling computer and disastrous to pull positive cable as U still got the alternator turning and pushing power, where is it gonna go. Just saying. Stay away from a 1970's way of checking an alternator on these 6,000 lb 4 wheeled computers. But yer ride, do as U see fit.

 

[RamDiver]

THAT's an old GM trick, where PPL would pull the "NEGATIVE" (not positive) cable, and if vehicle still ran the general consensus was the alternator was still good. This goes back to the old black box voltage regulators mounted on the firewall.

Yup, I remember.

Back in the days when you could drive a car without a battery connected.
Been there, done that more than once.

.