Some common problems that can occur with diesel engines include:

1. Hard starting: Difficulty starting the engine, which can be caused by issues with the fuel system, glow plugs, or air in the fuel system.
2. Poor performance: Reduced power or acceleration, which can be caused by issues with the fuel system, air intake, or exhaust system.
3. Excessive fuel consumption: Using more fuel than usual, which can be caused by issues with the fuel injectors, air intake, or exhaust system.
4. Excessive smoke: Excessive smoke from the exhaust, which can be caused by issues with the fuel system, injectors, or combustion chamber.
5. Engine knock or ping: Unusual noises coming from the engine, which can be caused by issues with the fuel system, injectors, or air/fuel mixture.
6. Overheating: Engine running too hot, which can be caused by issues with the cooling system, low coolant levels, or a clogged radiator.
7. Warning lights: dashboard warning lights that indicate a problem, such as check engine light, low oil pressure light, or coolant temperature warning light.
8. Leaks: Oil or coolant leaks, which can be caused by issues with gaskets, seals, or hoses.
9. Vibration: Engine vibrating excessively, which can be caused by issues with the engine mount, drive belts, or imbalance in the rotating components.
10. Power loss: Loss of power, which can be caused by issues with the turbocharger, exhaust, air intake, or fuel system.

Additional common problems that can occur with diesel engines include:

11. Clogged diesel particulate filter (DPF): A filter that captures particulate matter in the exhaust, a clogged DPF can cause the engine to run poorly or even stall.
12. Injector failure: Injectors that are not working properly can cause poor engine performance, increased fuel consumption, and increased emissions.
13. Timing problems: If the timing of the engine’s components is not correct, it can cause poor engine performance and increased wear on the engine.
14. Low compression: Low compression in one or more cylinders can cause poor engine performance, hard starting, and increased fuel consumption.
15. Fuel contamination: Poor quality or contaminated fuel can cause damage to the injectors, fuel pumps, and other parts of the engine.
16. Oil leaks: Oil leaks can occur due to worn or damaged seals, gaskets, or hoses, which can cause damage to the engine and lead to reduced oil pressure.
17. Fuel system problems: Issues with the fuel system such as clogged fuel filters, air in the fuel lines, or a malfunctioning fuel pump can cause poor engine performance and difficulty starting the engine.
18. EGR system problems: The EGR (exhaust gas recirculation) system is designed to reduce emissions. A malfunctioning EGR system can cause poor engine performance and increased emissions.
19. Alternator or battery issues: A malfunctioning alternator or battery can cause the engine to fail to start or run poorly.
20. Abnormal noises: Unusual noises such as knocking, ticking, or squealing can indicate problems with the engine and its components.

It’s important to remember that these are some of the common problems that can occur with diesel engines, but not an all-inclusive list. Regular maintenance and monitoring of the engine’s performance can help identify potential issues and prevent problems from occurring.