2010-03-01
Fault phenomenon:Take oneDaewoo excavatorWhen the engine is set to high throttle and the forearm is extended for recovery operation, the maximum decrease in speed indicated is 400rpm compared to 2000rpm. Black smoke occurs when the forearm recovers overflow.
Cause analysis:
① Speculate the malfunction related to SCV and confirm that there are no abnormalities in the display and actual measurement of common rail pressure. However, it is confirmed that there is no boost at this time.
② Checked the air intake once and found no abnormalities in the piping connecting the air filter and turbocharger.
③ No abnormalities were found in the turbocharger through visual and tactile inspection.
④ Checked the air intake twice and found oil in the piping. Due to the formation of negative pressure at the secondary air intake, oil mist was inhaled.
⑤ Upon inspection of the surroundings of the turbocharger, it was found that the C-ring securing the exhaust bypass valve shaft had come loose.
Detailed Fault Phenomena
Due to the detachment of the C-ring, the exhaust bypass valve remained open, causing the exhaust gas to escape towards the muffler. The turbine cannot rotate, and negative pressure is formed at the intake due to the resistance of the impeller, resulting in insufficient intake air.
Solution:
Install the C-ring and replace the piping with oil mixed in.
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