Diagnose difficulty in starting

[BlueMule]

I remote started my 2017 6.4L just now and the first attempt she wouldn't catch and sounded very weak on the cranking. Second remote start was weak crank as well but she caught and blew excessive white smoke (probably unburnt gas from the first failed attempt). At the hardware store a key start had a weak crank as well but she started. Check engine light is on. Amp gauge has the needle right in the middle. I'll go out and check the battery, but all interior lights are bright, she idles, runs/drives perfectly fine so it doesn't seem to be the alternator.

 

[BlueMule]

Plenty of juice in the battery

 

[thomas5853]

Oh wow, wonder what it could be if the battery is good.

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[RandomRam]

Have the battery load tested. Just because it has voltage doesn’t mean it’s good.

 

[BlueMule]

My super-smart in the automotive dept neighbor came over and had the same thought. He held the multimeter while I tried to start and the battery voltage dropped down to 7V. Just charged the battery back up and we're going to test to see if it's the alternator or the battery.

Have the battery load tested. Just because it has voltage doesn’t mean it’s good.

 

[BlueMule]

Battery!