Ram 3500 won't start

[RyGuy21]

Hello! My Ram 3500 turbo diesel won't start. Batteries at 11.68V. After glow plug preheat, it doesnt even try to crank. A pop is heard over the speakers followed multiple warning lights visible on the dash. That's it. Cleaned battery connections. Checked fuses. Disconnected batteries for 2 hrs thinking a reset may do the trick. Nope. Stumped.

 

[Daw14]

Needs batteries.should be 12.6 volts sitting, may also have other issues. Have batteries load tested then charging system checked.

 

[tjfdesmo]

11.8 volts is basically dead. You likely need batteries. Separate the two batteries, then charge and load test them independently. If one is bad, replace both.

Also, you don't have glow plugs.

 

[nlambert182]

What they said.... batteries are toast.

 

[RyGuy21]

Needs batteries.should be 12.6 volts sitting, may also have other issues. Have batteries load tested then charging system checked.

Hey Daw14, tjfdesmo and nlambert182;

Thanks so much!

I borrowed a OBD2 and it reported "p2509 ecm pcm power input signal intermittent". I looked that up and it said to start with the batteries. I have a Schumacher battery charger and it said one of the batteries was sulphated. So I swapped it out for 12V marine I had, albeit with different (slightly smaller values) CCA, RC, and Ah... but it was all I had and I was on an island with no way off and no way to get a tow truck in. So... I pulled both batteries and put them on the Schmacher separately to at least get the SOC of both to 100%. Then I dropped the batteries back in, boosted it and voila! So thank you very much for pointing me to check the batteries.

Funny thing these Rams... the batteries seemed strong as the lights were good and it all seemed to work except it would not crank. Then with all the error codes on the dash after pushing the start button I was fearful it was a bad computer. But it turns out the the computer needs to see a certain voltage or it will not send current to the start relay. So it seems... that is my theory anyway.

Also, I thought my Ram had glow plugs but that "wait to start" delay is to allow the grid heater to warm up the air inside the combustion chambers. Didn't even know "grid heaters" were a thing but Ram used them from 2007 to 2024. Ram has since switched back to glow plugs.

Learned something new today