What engine? My 4.8 barely cranks and just starts right up. I touch the button and let go right away and it starts right up on its own.

You're starter is engaging and cranking so battery/starter issues do not appear to be the problem, it seems more like it's not getting any fuel. If you keep cranking for so long I can see it dragging the battery down then combined with short trips perhaps she's not charging up all the way, but by the video that does not seem to be the issue..

...seems more like a fuel transfer pump not getting fuel from the tank to the injection system (old school diagnosis) or something of that sort..air flow restriction...spark/distribution issue (almost like there's no spark from the plugs)...can't believe dealer can't hook it up and find an issue...

...if the subs, amps and stereo have been in the car for a while, then unless something new has happend with the wiring to short something out I don't know how they could have had a progressive effect on the car, but the stealer will probably use that (again) as an excuse or source of the trouble even if it's not...

How much fuel have you run through the car since this started? I'm wondering if a bad load of fuel could be a problem..had an ML430 years ago and gas station dumped diesel in the premium tank...got a new engine from BP for free!!! That was easy cause it didn't take but 5 minutes to realize there was a problem and i was sitting there in the service station when she went "BOOM", there were about five of us with that problem!!!!I've also had water in my fuel that has been too much for fuel filters to stop and caused issues...maybe worth checking as well...some gas stations will be up front in admitting there is a problem.

Then again the stealer charged you $900 for a battery....IMO I'd park it at the stealers and say fix it, and give me my $$ back for a battery I didn't need or prove that it was the problem.

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