Sounds like you may have an injector stuck open and flooding it out, thats why when you have the gas pedal to the floor it tries to start or starts. If you put a fuel pressure gauge on it, Fuel pressure should be around 36 psi. After you shut the truck off or after you stop cranking. Watch the fuel pressure see how fast it drops. It should hold fuel pressure at 36 psi for at least 5 mins maybe more. Feel free to ask me any more questions.. Gl
