So it all started jumping a friend with a Ram 2500 with a Cummins. Turns out he's a genius and battery cables were loose and my truck was giving full juice. As a result when he tried to crank his truck over my truck instantly died at idle. I revved it a few and as he ran the grid heater/tried to start it I could see my voltage guage struggling. We realized his battery cables were loose, tightened them up and he was on his merry way.

Now I then drive 50 miles home. Turn the truck off and it sits for 6 hours. I hop back in it and it fires for a quick second, maybe half a second and turns off. Fire it back up again and was fine for the next 3 weeks until today.

Today I hop in my truck as it sits for a week at a time every week and only driven on weekends, and she starts for half a second again and dies again. I try it again and just keeps cranking... So I crank it for another 10 seconds and kill it. Play with the battery cable, nothing. So as I'm cranking it I give it some gas pedal and after a rough start of barely firing a couple times she fires up I keep it alive like 1500 rpm for 10 seconds and she goes to idle like normal.

I drive home like almost nothing happened but I did notice that every time I let off the gas the truck doesn't just go to a normal 900-1100 rpm. It goes down to about 500-600 and then back up to 900, like what happens if you drain the battery and don't let the truck recharge the battery for 20 minutes or so. But besides that, the truck drove 50 miles home.

Anyone think its the alternator, or possibly a TPS. Any input would be greatly appreciated.

 

Is the volt gage showing the battery charging? The diesel is much more demanding when it comes to starting, so, the current draw is pretty horrendous.

I would be tempted to clean the throttle body, (battery disconnected) and let the truck relearn idle. I *think* that should solve the issue, providing everything else is working as it should.