I'm a mechanic of 30+ years, I changed head gaskets on a 2004 hyundai santa fe 2.7 , without problem,put back together, crank sensor was bad, insulation all gone off wires, so I changed that, the car will not run, when you turn key over its starts, but as soon as letting key go, it wont stay running, I've hooked the scanner up to it, and nothing, no check engine lights are on or anything, I'm stumped.