I am trying to determine what is up with my truck. it has started to hesitate.

Thanks for your response, do you think that would prevent my truck from starting. It turns over put will not fire now at all (the good news it likes being in the garage because it made it home before it went on vacation). So I read that I can do a fuel pressure test and with the key on (not the engine) it should read on test kit analog gauge. No reading no fuel, correct?

If it's not starting at all fuel issue could be the problem. Fuel pumps are common failure item. If you cycle the key, you should have some fuel pressure show on the gauge. Your initial description sounds like a restricted exhaust. as you drive the vehicle, the increase heat in exhaust causing the restriction to get worse, to the point the engine won't run. Exhaust cools and cycle starts all over. Only take 3 psi in the exhaust to affect engine performance.

Again thanks for the response. I did a fuel pressure test (actually three times) On the first test it did read about 10 psi and a small amount of fuel needed to be released from the test gauge unit. Each test after that test read 0 psi and no fuel was in the test gauge unit (each time with key on and cycling the key switch). I replaced the relay and no change. And since it is an electrical part I now have a spare relay, lol. So I am going to assume the fuel pump needs to be replaced. Would you agree? Okay, it's been a couple days, I have tried to start my truck a couple of times with no luck until today. Yes, it's Sunday. My truck has turned over and not fired since Tuesday or Wednesday, but it has today and morn than once. Any thoughts?