First, is the check engine light on while the truck is running? If not, does it come on with the key on? If the light is on, you need to find out what the code is. If no check engine light, at 300,000 rounds could be it needs a set of injectors, but first clean out the sediment bowl. Behind the fuel filter on the left side of the engine is a blue cylinder about 3 inches long. It hangs from a bracket and is made of plastic. Unthread it and clean the screen you find inside, and don't loose the O-ring. If it comes off hard, use a closed end 11/4 wrench. Don't crack it, but if you do you can get a new one. Nobody ever cleans these things out and it is the first thing a tech will check. Next check the check valve on the back of the head. If that leaks, the fuel will drain out of the head overnite and will cause the problem you are having. Look for the return fuel line where it comes off the back of the head. The thing it is bolted to is the check valve. when you take it off, don't loose the copper washers, and make sure you put it back together right. There is a ball valve in there with a spring to hold it in place. It must seal tightly to keep about 30 psi in the head at all times.
