Now I'm just throwing darts, so apologies if I'm way off ...
When you say "shut off" ... do you mean like a light switch? Just powered off? No catastrophic mechanical grinding or metal to metal sound of any kind?
The previous generation of NCV3 engines, like mine, would experience failures in the engine wiring harness over time. The wires would dry out and crack, causing a short. When mine started to fail, it would stall. It stalled intermittently for weeks. It would stall at highway speed, where I would just coast to the shoulder. Shut it off and it would start right back up again. I stalled right smack in front of the Holland tunnel on a Sun afternoon. Once I changed the wiring harness, it was all good. Idk of they addressed that issue on later generations of the engine. Idk how much that specific harness is ... I imagine anywhere from $750-$1,100 .... ?? Labor will probably double that amount.
A bunch of $$ can be spent on diagnostics going down rabbit holes on these things. Depends if the shop is charging $100 per hr or $160 per hr. Problem is, if they're on the wrong track ... 1.They might not admit it unless you prove them wrong. 2. It's an uphill battle getting the invoice reduced for their wasted time.
Anyway, hope it goes well ...
Sprinter source is a good resource ....
