High-Probability Issues:
* Injector Control Pressure (ICP) Sensor: This sensor monitors the high-pressure oil system that feeds the injectors. A faulty ICP sensor can lead to erratic fuel delivery, causing rough running and stalling. The PCM (Powertrain Control Module) relies heavily on this sensor's readings. Have the ICP sensor checked for proper voltage and resistance readings. A replacement is relatively inexpensive.
* High-Pressure Oil System (HPOP): The HPOP is responsible for pressurizing the fuel injectors. If it's failing, it might provide enough pressure for a cold start but not enough after the engine warms up or is restarted. This is often diagnosed with a pressure gauge connected to the ICP sensor port. Low pressure points to HPOP issues, which can be costly to repair.
* Crankshaft Position Sensor (CKP): This sensor tells the PCM where the crankshaft is in its rotation. A faulty CKP sensor can cause misfires, rough running, and stalling. It's relatively inexpensive to replace.
* Fuel: While less likely given the symptoms, ensure you're using high-quality diesel fuel. Water or contaminated fuel can lead to similar problems.
* Wiring/Connectors: Check all the wiring and connectors related to the fuel system and sensors mentioned above. Corrosion or loose connections can cause intermittent problems.
* Glow Plugs (less likely for restarting issue): While glow plugs are primarily for cold starts, faulty glow plugs *can* contribute to rough running, especially when the engine is cold or warm.
Less-Likely (but possible) Issues:
* PCM (Powertrain Control Module): A failing PCM is a less common but possible cause. This is usually a last resort diagnosis and requires professional testing.
* Fuel Filter: A clogged fuel filter restricts fuel flow, but this usually causes more consistent poor performance rather than intermittent stalling.
Troubleshooting Steps:
1. Check the obvious: Make sure the fuel tank isn't low. Inspect the fuel filter for visible signs of contamination or restriction.
2. Read the Trouble Codes (DTCs): Use an OBD-II scanner (capable of reading codes for a 7.3L Power Stroke) to retrieve any diagnostic trouble codes stored in the PCM. This will give valuable clues.
3. Test the ICP sensor: This is often the first place to start. Check voltage and resistance readings against factory specifications. A simple test is often enough to rule it in or out.
4. Monitor the ICP pressure (requires a gauge): If you have access to a pressure gauge, monitoring the ICP pressure during starting and running will help determine if the HPOP is functioning correctly.
5. Inspect the wiring: Look for any broken, frayed, or corroded wires or connectors in the fuel system and related sensor circuits.
6. Check the CKP sensor: If ICP tests good, a faulty CKP can be the next culprit.
Professional Help:
If you're not comfortable with automotive diagnostics, a qualified mechanic specializing in diesel engines, especially Ford 7.3L Power Strokes, is recommended. These engines have specific quirks, and improper diagnosis or repair can lead to more significant damage.
Important Note: Avoid driving the truck excessively while experiencing these symptoms, as continued operation with a faulty fuel system component can damage the engine.
