This article explains how to troubleshoot excessive black smoke on a Caterpillar  325c excavator

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    \  (1) Possible reasons. 

 1) Intake and exhaust systems. 

 2) Engine speed/timing. 

 3) Air pressure sensor. 

 4) Turbocharger outlet pressure sensor fuel configuration and/or "FRC fuel limit value". 

 5) Personality module. 

 6) Fuel quality.

(2) Recommended measures. 

 1) Intake and exhaust systems. 

 ① Check whether there is any throttling or leakage in the air intake system. 

 a. Connect the Caterpillar Electronic Technology (Cat ET) to the service tool connector. 

 b. Compare the readings on the air pressure sensor and the turbocharger compressor inlet pressure sensor. 

 c. Check whether the filter is throttling.

  d. Check whether there is load reduction operation or alarm.

  e. Visually inspect the system for throttling and/or leaks. 

 ② Confirm that the turbocharger is not faulty. 

 ③ Check whether the exhaust system is throttled. 

 ④ Repair any leaks found. Remove any discovered throttling. Replace any damaged parts.

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2) Engine speed/timing.

  ① Check the calibration of the engine speed/timing sensor, please refer to the "Calibration of the Engine Speed/Timing Sensor" section.  

② Check whether the positioning between the crankshaft and the camshaft drive gear is correct.

3) Air pressure sensor. Check the air pressure sensor for dirt and/or debris. Remove any dirt and/or debris. The air pressure sensor should be between 50~ between 100kPa.

4) Turbocharger outlet pressure sensor, fuel configuration and/or "FRC fuel limit value". 

 ① When the engine is running at full load, monitor the "Fuel Configuration", "Rated Fuel Limits" and "FRC Fuel Limits" on the Cat ET. If the "Fuel Configuration" is equal to the "Rated Fuel Limit Value" and less than the "FRC Fuel Limit Value", it means that the electronic components are working properly. Otherwise, proceed to the next step. 

 ②Monitor whether the "boost pressure" and "atmospheric pressure" on Cat ET are working properly. When the engine is stopped, "boost pressure" should be

OkPa. NOTE: FRC failure will cause black smoke only when accelerating. When running smoothly, an FRC failure will not cause black smoke. 

 5) Personality module. Verify that the correct personality module is installed.

6) Fuel quality. Check fuel quality. If necessary, change the fuel to one with a higher cetane number.

  When the temperature is below 0°C, check for solidified fuel (wax).  

7) Valve adjustment. Check the valve clearance adjustment.