Hello all,

Hoping for some help in diagnosing what happened and where to start looking.

First of all, I have a 2016 with 3500K. I got her used about 500k ago and am not sure what if any work has been done.

Ok, she was running strong at about 70k during a 10 minute drive, when I started to notice an occasional hesitation about half way through the trip, almost as if the engine stopped firing for a revolution or two.

About a minute later, there was a dramatic loss of power, and the engine sounded like it was either starving for air or unable to vent exhaust. She ran for about 15 seconds more after that on a flat road but when I tried going up a hill the engine quit.

Restarting would only turn the crank a few turns before it wouldn't turn anymore. I tried restarting a few more times after that but when it would only crank a half turn I stopped trying.

There was one time about a month before this happened where there was a similar starting problem, but was able to get her started on the third try.

There are no efi codes, I can hear the fuel pump pressurize the system, I have replaced the fuel filter and cleaned the air filter (it wasn't that dirty). It still only turns a revolution or two and does not fire.

My next thought is to pull the plugs and check the valve clearances, but I thought I'd ask the experts here before doing that.

Thanks in advance for your advice!

First thoughts are low voltage given that the thing won't turn over. How old is the battery?

The battery is definitely not stock, so I'd guess it isn't more than a year or two old. It's also possible the CCA is lower than the original, but it rarely if ever drops below 20c this time of year.

Could a flaky regulator/rectifier cause symptoms like this too?

The starter on these things don't draw much current. The engine should spin over easy and for a long time on a good battery. if it doesn't, the battery hasn't the capacity to be trust worthy.

These systems are finicky in low voltage situations. I would first charge the battery and then start the machine and measure the charging voltage.

If charging is good, replace the battery.

If not charging, under charging, or over charging, replace the regulator. Have the battery load tested and replace if necessary.

Update-

New lithium battery with more cca than stock, new plugs, new regulator/rectifier and new coils... same problem.

She'll crank all day after removing the plugs. Thinking some kind of valve issue?

Did you do any diagnostic work  before replacing parts? Doesn't sound like it.

Guessing can be expensive.

Compression check. Fuel pressure check. Timing check. Sensor checks. etc ....  until you find a problem.

Else, bring it to the service department at least for diagnostic work. It may end up being cheaper in the long run.