What specific parameter should be checked when diagnosing diesel engine knocking?

When diagnosing diesel engine knocking, the specific parameter that should be checked is the fuel injection timing. Diesel engine knocking, also known as diesel knock, is often caused by the fuel igniting too early in the combustion cycle. This premature ignition creates a rapid pressure rise inside the cylinder, resulting in a characteristic knocking sound. Incorrect fuel injection timing can be due to several factors, including worn fuel injectors, a malfunctioning injection pump, or incorrect timing settings. To diagnose diesel knock, a technician would use specialized diagnostic tools, such as a timing light or electronic diagnostic equipment, to check the fuel injection timing. If the timing is found to be incorrect, it must be adjusted to the manufacturer's specifications. Other factors, such as incorrect fuel grade, low cetane number, or excessive carbon buildup in the cylinders, can also contribute to diesel knock, but fuel injection timing is the most common and critical parameter to check first.