High-Probability Issues:
* Fuel System:
* Low Fuel: Sounds obvious, but check your fuel level first. A low fuel level can cause starvation, especially during idling or when the fuel pickup is at a low angle (like in reverse).
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to stalling, particularly under low-demand situations like idling. Replace this regularly as part of routine maintenance.
* Fuel Pump (Lift Pump): The lift pump provides fuel to the injection pump. A weak or failing lift pump won't supply enough fuel at low engine speeds. Listen for a consistent hum from the pump – a weak or intermittent sound suggests a problem.
* Injection Pump: Problems within the injection pump itself, such as worn components or low fuel pressure, can cause stalling, especially at low RPMs. This is a more complex and expensive issue to diagnose and repair.
* Electrical System:
* Battery/Alternator: A weak battery or failing alternator can't provide enough power to run the engine consistently, leading to stalling. Check the battery voltage and have the alternator tested.
* Wiring/Connections: Corrosion or loose connections in the electrical system can interrupt power to vital components, causing stalling. Inspect all wiring related to the engine and fuel system.
* Crankshaft Position Sensor (CKP): A faulty CKP sensor won't provide the engine computer with the correct information about engine position, leading to misfires and stalling.
* Air Intake System:
* Air Restriction: A clogged air filter restricts airflow, leading to poor combustion and stalling. Replace the filter.
Less-Likely (but Possible) Issues:
* Transmission Issues (Reverse Only): If the stalling *only* occurs in reverse, there might be a transmission problem. However, since you mention idling issues as well, this is less likely to be the primary cause.
* Vacuum Leaks: Vacuum leaks can affect various engine functions, potentially leading to stalling, though this is less common in diesels.
* Governor: A malfunctioning governor could cause irregular engine speed and stalling. This is less common but still possible.
Troubleshooting Steps:
1. Start with the Simple Stuff: Check the fuel level, replace the fuel filter, and inspect the battery and connections.
2. Listen to the Engine: Pay close attention to any unusual sounds – knocking, clicking, or a weak fuel pump hum.
3. Check Codes: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored by the engine computer. These codes can provide valuable clues. Note that older Cummins engines may not fully support OBD-II.
4. Fuel Pressure Test: A professional mechanic can perform a fuel pressure test to determine if the fuel system is delivering adequate pressure.
5. Consult a Mechanic: If you're not comfortable tackling this yourself, a qualified diesel mechanic is essential for diagnosing and repairing more complex issues, especially those involving the injection pump.
Remember that diagnosing diesel problems can be complex, and attempting repairs without the proper knowledge and tools can be dangerous. Safety first!
