2005 nissian frontier trouble starting in the cold

I own a 2005 nissian frontier that I bought in CA. I now live in ND where it will not start if it is below freezing. I have had an oil change, new battery and terminals cleaned, coolant flush and refill, crank shaft replacement and also a transmission rebuild for a different problem early to do with a super chager. It is again in the shop where they are able to start it inside but not out in the cold. They are still trying to find out what is wrong but said they keep running into dead ens. Was wondering of anyone had any idea what could be the problem and any solutions as well?

To start you need fuel, and to deliver that you need a functioning fuel pump. Your pump may have been on its last legs and the severe N D weather may have been the last straw.

Your shop is obviously missing something.

As many here will agree, fuel and a hot spark is what you need.

I would try a more competent shop, preferably one which understands superchargers.

Does the engine turn when the starter is engaged? Putting a fuel pressure guage on it when it is cold would tell you if the pump is bad.

If it won’t crank at all, the first thing to do is measure the voltages at the two starter motor electrical terminals during attempted cranking. Both should be above 10.5 volts. Has the shop done that measurement?