OK. 1996 Ford Explorer replaced computer, water pump, ETC, plugs, plug wires, and starter. Put in head/lock sealant in coolant -new coolant. Hard to start once started will start as long as motor is warm once motor cools off hard to start ,also backfires while trying to start. If has set for a while white steam out of exhaust. Is this a blown head or head gasket? About to take to junk yard very frustrated!! HELP PLEASE ANY OTHER IDEAS?

Have you done a computer test to determine if there are any other issues?

It could be one of your temp sensors, there is on for the computer and one for the coolant. What it could possibly doing is the computer is sending enough fuel to crank it based off the temperature of the block. If the sensor is reading that the block is always warm, it will send a certain amount of gas to start it, even if the block is cold, which means that it is not sending enough to crank it.

What I meant about the block being cold and the fuel delivery, is the computer is always going to correct for a warm block, sorry if I confused you.