When I try to start the car in the morning, after it sat for the night, there are no issues. However, the car develops starting issues as soon as the engine warms up a bit. So, if I drive for a while, then stop and park the car shortly, when I am about to keep driving, the car just cannot start right up. So, I have to try several times and it will eventually start but it would run kind of rough. What could be the problem?
It’s possible you have a leaking fuel injector - which is losing the residual fuel pressure in the fuel line. The fuel leaks into the cylinder, but leaves you with a partially filled fuel line. Diesel fuel injectors, when working properly, require great pressure to "fire" or inject fuel into the cylinder. If the injector is leaking down, it take the fuel pump a small amount of time to refill the fuel line, and deliver the pressure required for the injector to work properly. Have a mechanic who is training on diesel engines diagnose the starting problem so that this gets corrected properly.