Q: Fuel pump

Make sure the fuel gauge is actually accurate. Maybe "half a tank" is "empty"? It is relatively easy to rule out the fuel pump by testing the pressure on the fuel rail but that will not tell you anything about whether the injectors are actually delivering fuel. However, if the truck "sometimes" runs smoothly, it is probably not the injectors but rather a fuel delivery (pump, pressure regulator) issue, an ignition fault, or an issue with malfunctions in the air induction system, such as the throttle position sensor, mass air flow sensor, idle air control and so forth. To get this diagnosed and resolved, the recommended service is an engine stalling diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.