My Neighbors L6060 was shutting off after a few minutes .
We finally figured out it was the pull apart connector for the electric fuel pump .
The pump was only running every so often and the Tractor was slowly running out of fuel.
I once had a new MF 2635 that was delivered with a similar problem.
Electrical connection to lift pump was intermittant and engine would occassionally loose power and sometimes start blowing white smoke. Of course, it would run fine when trying to diagnose it.
Eventually, it failed significantly enough that it could be diagnosed.
FWIW, this new tractor was delivered with several obvious problems as dealer had taken MFs PDI money but had done absolutely nothing.