My Engine cranks over but will not start?

I have 2004 Hyundai Santa Fe, 2.4L DOHC. Without warning it just quit running while driving and now won't start. Why and what do I do to fix it.

Engine problem
2004 Hyundai Santa Fe 6 cyl Wheel Drive Type unknown Automatic 70000. Miles

I hit a 3x2 ft. X12" piece of concrete coming at me on the interstate at 70mph. Anyway, I couldn't avoid and upon impact-other than the 2 destroyed front tires, the car lost power before I pulled over to the side of the road. Now, the mechanics say it won't start. There were no fluids found under the vehicle when towed, and, the car always purred like a kitten prior to this. The vehicle has always had regular oil changes, tire rotations, transmission fluid changes, etc. No VISIBLE damage underneath. There is power (windows, lights)- but will not turn on. Could it be a sensor thing? Maybe the gas line got disconnected? Any ideas? HELP!

Pretty sure there's an inertia switch (turns off the fuel pump when you run into something)...it should be mounted on the left strut - right next to the master cylinder. The button pops up when it is activated - just push the rubber button down to turn the fuel pump back on. Car should start.
This picture is from a 2002 model:

I have a 2004 hundai santa fe and since it got really cold this summer whenever I put gas in my car it wont start but after about 3 times of trying it finally starts and then after its ok until the next time I am at the gas station. Could it be because of the cold or could it be because I have been using a lower grade gas? Or is it somthing else?

The check engine light has never come on. When we bought the car in the summer it never happend but recently we have had below 0 temps and we always us low octane fuel when it calls for high. Its really wierd

Four cylinder two wheel drive automatic 72,000 miles.

My car will not start. The relay for the fuel pump is not getting power but it can be bypassed and the fuel pump starts right up. When I try to start the vehicle after bypassing the relay it still will not start. I have also checked the inertia switch and it has not popped up. It has gotten regular fluid changes and has always run like a champ before. I am stumped as to what it could be.

How do I check the computer to see if that is it? Or would it be better just to reset the computer? If I do have to reset the computer how do I do that?

Would the relay also cause the spark plugs to not fire? If not what would cause it? They are not working even if I bypass the relay.

I just finished checking all the fuses and relays and there all good. Is there another component that controls the fuel pump and ignition coils before the fuse box that could of gone bad?

Where is the sensor located?