black smoke and lumpy idle

[Sean Connolly]

I HAVE AQUESTION AS TO RECENT CHANGE IN IDLE ON MY PORT 1999 6BTA. MY PORT HAS 1000 HOURS, AND AFTER MY LAST OFFSHORE TRIP 7 HOURS RUNNING AT 2400RPMS AND 8 HOURS OF TROLLING 900 TO 1300 RPMS, I NOTICED BLACK SMOKE AT IDLE AND A LUMPY SURGING LIKE IDLE, NO SMOKE WHEN MOTOR IS ON BOOST AND EGR TEMP IS THE NORMAL  900 RUNNING ON PLANE, I CHANGED FUEL FILTERS AND KNOW I HAVE GOOD FUEL, I BELIEVE I HAVE ONE OR MORE INJECTOR STUCK OPEN AND THE SMOKE IS UNBURNT FUEL, HOW CAN I TEST THE INJECTORS OR DO I HAVE TO SEND OUT THE SIX OF THEM?

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[Francis Valerio]

also,  there is a way to test them in the Cummins B series manual.  I guess google it if you dont have the manual.  I recommend removing the injectors yourself and bringing them to a diesel shop.  Make sure they are certified Cummins and they should be able to see the PSI they pop at etc…

[Francis Valerio]

ALL B-series when trolling at lower RPMs tend to load up a bit.  At idle the engines do NOT stay at operating temperature and combustion temperature are not where they need to be.

Over time this can lead to carbon build up on the tops of the pistons and injector tips.  If your injectors have not been serviced I would start there because they are easy to remove and inspect and have them tested as well…we are talking about LOW hour BUT 23 year old engines and injectors

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