Cranked to warm up, went to go to work and had shutoff. Now it wont crank at all and spits back through air intake

Lots of possible reasons. Let's first see if the problem is fuel related. Spray a little engine starter fluid, just a little, into the air intake, and crank right away (before it evaporates). If the engine runs for a second, or even if it just coughs a little, your problem is fuel. For instance, out of fuel, or not being pressurized by the injector pump, or fuel shutoff valve is not opening. More information would be nice to have. Are your glow plugs working? Is the weather very cold?

Check for fuel, air intake clear, spark/compression,

Sometimes if it set too long the gas went bad. You may have to drain the gas and the put fresh gas in.

It won't stay cranked? or Want?
are you talking about your STARTER or do you mean KEEP RUNNING?
Can you clarify so I can help you. I have a great understanding of the 4.0 Engine on the Ford Explorer

Did you get the oem parts from the dealership? If you got cheap ones at the auto parts store that is the problem. Now you have to buy them again.

these engines do have the a bad upper plenum problem, but what it sounds like may be a ignition control module, or the crank sensor. these are the cheaper ones to fix rather than the upper intake.to take the guessing out, have the cooling system filled up all the way, and then pressure test it. it should hold atleast 15psi at all times, and if it does not then there is a leak in the system. if nothing sprays out around the engine, then yes it could be the upper intake especialy if its the 3.8, os 31., and or the 3.4, but Im sure you have the 3.8. there was a recall on these engines intakes, but most of them where out of the mileage range for free service. good luck hope this helps

Pull your air intake and spray some starter fluid directly into the honeycomb, then crank it over. This may work, it did for me.

When you turn the key front. Listen for the fuel pump to prime. It should sound like a low humming noise that lasts about 3 seconds. If it does then check for spark by pulling one of our sparkplug wires and putting an extra spark plug in it. Place the end of the wire down somewhere safe and crank the motor. If you can't seek spark in the plug, it is most likely your coil failing. So, check fuel pump and fuel pump relays first, then spark. Good Luck.

Try spraying starting fluid into the intake of the air cleaner while someone else starts the car. Keep a continual spray going while the car is cranked. If the car starts more than likely the fuel pump went out.

Try spraying with starting fluid. If it starts, it is your fuel pump that is not working. Good luck.