* Evaporative Emission System (EVAP) problems: A faulty EVAP system can cause a pressure buildup in the fuel tank. The pump will shut off as a safety precaution to prevent fuel spillage. This is a common cause. Check for leaks in the EVAP system lines and canister.
* Rollover Valve: This valve prevents fuel from spilling if the truck rolls over. A malfunctioning rollover valve could be restricting fuel flow, causing the pump to shut off.
* Clogged Fuel Filler Neck: Debris, rust, or a kink in the filler neck can restrict fuel flow.
* Faulty Fuel Tank Pressure Sensor: This sensor monitors pressure in the fuel tank and communicates with the on-board diagnostics (OBD) system. A faulty sensor could give incorrect readings, causing the pump to shut off.
* Charcoal canister: The charcoal canister is part of the EVAP system. A clogged or faulty canister can cause pressure issues.
* Fuel Pump Issues (less likely): While less likely to cause the pump to *immediately* shut off, a weak fuel pump could be struggling to pull fuel, leading to the pump sensing a restriction and stopping. This would usually be accompanied by other symptoms (poor engine performance, hard starting).
* Gas Cap: Though less likely, a loose or faulty gas cap can disrupt the EVAP system and cause the problem. Try tightening it securely.
Troubleshooting Steps:
1. Check the gas cap: Make sure it's tightly sealed.
2. Inspect the filler neck: Look for any visible obstructions or kinks.
3. Check for EVAP system codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs) related to the EVAP system.
4. Have a mechanic check for fuel pressure: They can test the fuel system pressure to rule out pump or pressure sensor issues.
5. Inspect the rollover valve (more advanced): This requires some mechanical knowledge and may necessitate professional help.
Important Note: Ignoring a problem like this can lead to more serious issues, possibly even a fire hazard. It's best to have a qualified mechanic diagnose and repair the problem as soon as possible. Don't continue trying to fill the tank until the cause is identified and fixed.
