This morning it got down to below 20 degrees for the first time since I have had the truck and forgot to plug it in. Went out let the grid heater cycle twice. Tried to start it this morning and it wouldnt start. Then the batteries went dead, so I charged them up and plugged the heater in for most of the day and get home and it still wont crank. It has alittle under a 1/4 of a tank but I dont think that is the problem. Does anyone know what could cause it not to start? Its a 98.