2001 ford ranger after it sits for a few hours it

Could have been a stuck thermostat or a faulty water pump.
You may now have a leaking head gasket.

crank sensor

I had this same trouble with other cars and it was loose connection in wiring harness at plug in the fuel pump circuit. The wire connector was loose in the plug and would not always maintain contact. The symptom on mine was it would die when I hit a bump sometimes, but ran fine at all other times. It finally quit entirely and had to hunt for it.

Its not the oil, increasing temperature will thin out the oil. If it cranks easily but won't start it could be the spark plugs or the spark plug wires. When they heat up, especially if they are old, they won't perform well. Pull off one of the wires and hold it close to the plug, try to crank the engine and look for a spark. If it sparks them try removing a plug and check to see if it looks wet. If its bone dry it might not be getting fuel.

Ur truck's fuelpump needs an attention.

check the fuel pump and see is working properly, if the pump is good than the problems will be the crank sensor is faulty. what crank sensor does it sense the turning of the flywheel and it send a single to ecu, and ecu send a flow of power to turn on the fuel pump as long it sense the flywheel turning.

There are numerous items to check and eliminate in troubleshooting this. I will say that the ignition pick up coil in the distributor is a popular failure for your symptom.

have you tried changing you distributor and rotor

Check battery crank power.

try a little starting fluid in the air intake if this doesnt work check plugs for fireing