* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is in its rotation. A faulty CKP will prevent proper timing, leading to a start-then-die situation. It's a common culprit on these trucks.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A malfunctioning CMP will also disrupt timing.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF can cause erratic running or stalling, especially after starting. Try cleaning it first with MAF sensor cleaner (follow the instructions carefully).
* Throttle Position Sensor (TPS): Reports throttle position to the ECU. A faulty TPS can cause improper fuel delivery and stalling.
* Fuel Pressure Regulator: While you replaced the pump, the regulator (often integrated into the fuel rail or a separate component) could be failing, causing inconsistent fuel pressure. This could lead to starting but then dying due to insufficient fuel.
* Wiring/Connectors: Despite replacing components, check all wiring and connectors related to the fuel system, ignition system, and sensors mentioned above for corrosion, damage, or loose connections. Pay close attention to grounds.
* Computer (PCM): Although less likely, a failing PCM can cause intermittent starting problems. This is a more expensive and involved diagnosis.
* Vacuum Leaks: Leaks in the intake manifold vacuum system can disrupt engine operation and cause stalling. Listen carefully for hissing sounds around the intake manifold.
* Fuel Filter (Though you likely checked this already): A clogged fuel filter can restrict fuel flow, even with a new pump.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any stored codes. This is the most crucial first step. The codes will often point directly to the problem.
2. Test the sensors (CKP, CMP, MAF, TPS): You'll need a multimeter or a scan tool capable of live data monitoring to check the sensor readings. Compare them to the specifications in a repair manual.
3. Check fuel pressure: A gauge is needed to accurately measure fuel pressure. It should be within the manufacturer's specified range. Check pressure both at start-up and during the stall.
4. Inspect wiring and connectors: Look for corrosion, broken wires, or loose connections in the fuel and ignition systems.
5. Test for vacuum leaks: Spray a carburetor cleaner or brake cleaner around the intake manifold and vacuum lines while the engine is running. A change in engine speed indicates a leak.
If you're not comfortable performing these tests, take it to a qualified mechanic. Replacing parts randomly is expensive and inefficient. Systematic diagnostics are key.
