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3126B - Random sudden loss and recovery of Engine Speed

Experiencing random loss and recovery of Engine Speed  Ran a Sea Trial with data recorder at 2100RPM, after 15 minutes first drop and recovery occurred, few minutes later two consecutive  events occured: Data showed a sudden drop of injection Actuation Pressure (3300 to 2500) lasting less than half a second. RPMs start going down and ECM initiates recovery by increasing injection actuation current. Engine reaches desired speed in about 10 seconds. There are no reorded alarms or codes of events and other parameters ( throtle position, desired speed, etc) remain steady.  Only change are in amps, desired inject ores and actual injection pressure as ECM recovers,

 

Initially suspected Injection Act. Pressure Sensor fault but would have expected engine to maintain or increase RPM as the current to the valve is increased. No oil leaks in HEUI pump are apparent. Events occur three or four times per hour, and only after engine has been run for more than 15 minutes at cruising RPMs.