Willing to bet that once the vehicle is in the heated shop and warms up, it will fire off like normal. Extreme cold like you're experiencing (is the -50C windchill or actual air temp?) can cause fuel line issues on top of the fact that the fuel/air mixture doesn't combust as well during start-up as in warmer temps. I live in MN and my Explorer sits outside. When it gets extremely cold, I won't let it sit for more than 4-6 hrs without starting it and letting it warm up. This is the third Explorer I've owned over the years that had to sit outside in the winter and on the absolute coldest days, I've even gotten up out of bed in the middle of the night to start them. Can't remember a time when they failed me when I needed them. Unnecessary wear and tear on the engine? First two reached 200K miles before rust took them. Current one brought up from AZ 12 yrs ago has 196K miles, no rust and no chain rattle that I can hear. I know the environmentalists would have a fit with my wasting gas, but in my mind it keeps everything under the hood "loose" for easier starts.