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Detroit 6V92 twin turbo

Old 10-24-2018, 03:48 PM
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Default Detroit 6V92 twin turbo

Black and grey smoke, replaced injectors, rebuilt both heads, new cylinder kit, over haul runs like crap and smoked, will not hold rpm gets to 1800 and falls off to 0 and shuts down??? Need help please.
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Old 10-24-2018, 03:59 PM
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Sounds like at least 2 issues . The shutting down sounds like a fuel restriction or sucking air . As far as smoking , the first thing I would check is the injector height/timing , its got to be right .
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Old 10-24-2018, 05:01 PM
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Originally Posted by prowlersfish View Post
Sounds like at least 2 issues . The shutting down sounds like a fuel restriction or sucking air . As far as smoking , the first thing I would check is the injector height/timing , its got to be right .

Replaced all the injectors, Jefferson in La did the injectors, it's been tuned up three or four times, but there is something that is being missed sucking air could be something, replaced fuel pump, checked all lines, had low fuel pressure, after changing pump got better. Thank you so much, will look at it tomorrow and any other help.
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Old 10-24-2018, 05:20 PM
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How much smoke are you getting? Have seen restricted fuel cause lightish smoke due to late injection and it would explain the shutting down. Heavy smoke would indicate something different. Has cam timing also been rechecked? Have seen failed blower drives as well do funny things but probably wouldn't allow you to make the 1800.
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Old 10-24-2018, 05:23 PM
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Check for air leak at fuel filter,
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Old 10-24-2018, 05:27 PM
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Also make sure fuel restrictor fitting is attached to head on fuel return?
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Old 10-24-2018, 05:50 PM
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Originally Posted by prowlersfish View Post
Sounds like at least 2 issues . The shutting down sounds like a fuel restriction or sucking air . As far as smoking , the first thing I would check is the injector height/timing , its got to be right .

Replaced all the injectors, Jefferson in La did the injectors, it's been tuned up three or four times, but there is something that is being missed sucking air could be something, replaced fuel pump, checked all lines, had low fuel pressure, after changing pump got better. Thank you so much, will look at it tomorrow and any other help.
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Old 10-24-2018, 05:57 PM
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Originally Posted by prowlersfish View Post
Sounds like at least 2 issues . The shutting down sounds like a fuel restriction or sucking air . As far as smoking , the first thing I would check is the injector height/timing , its got to be right .
The smoke is heavy at idle, and when you speed it up it really black smoke like it's under load that's at no load, have light fuel coming out of exhaust, tried to run and put load and it went about 100 yards and rpm's fell off and then shut down.
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Old 10-24-2018, 06:04 PM
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It could be an air restriction, Have you checked the intake and verified the turbo is working properly?
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Old 10-24-2018, 06:05 PM
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Originally Posted by prowlersfish View Post
Sounds like at least 2 issues . The shutting down sounds like a fuel restriction or sucking air . As far as smoking , the first thing I would check is the injector height/timing , its got to be right .
Ya when I pushed it up under load 1800 was on the pin when it should have been 2300 on pin so it wasn't even getting full throttle
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Old 10-24-2018, 06:09 PM
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The turbos seem to be working ok had some sutt but cleaned it out
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Old 10-24-2018, 07:58 PM
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To help rule out a fuel supply issue you can run the return line from the head into a remote container. There should be a steady flow of clean fuel (no air or combustion gas). If you have the line below the surface it will be easy to identify that as a problem. No or little fuel would indicate a restriction in the supply. Have on several occasions also found debris in the supply fitting at the primary filter which will cause that restriction.
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Old 10-25-2018, 04:52 AM
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Black smoke is unburnt fuel.
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Old 10-25-2018, 04:57 AM
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Originally Posted by LongIslandFisherman View Post
Black smoke is unburnt fuel.
which is why I don’t think it’s a fuel supply issue.
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Old 10-25-2018, 06:47 AM
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Originally Posted by LongIslandFisherman View Post
Black smoke is unburnt fuel.
Absolutely... If the fuel supply to a unit injector is restricted, it will retard it's injection timing. This will also cause incomplete combustion and smoke. It normally is not the heavy smoke you see on a coal burner though. Timing is critical on 2 strokes.
Low high idle rpm, low fuel pressure and dying are all fuel supply symptoms.
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Old 10-25-2018, 07:37 AM
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Lots of good suggestions above, several things you can do to rule out potential problems like running the fuel return line into a bucket.


I'd also run a bore scope through all the air passageways to make sure there are no obstructions. A plastic bag sucked in or an air obstruction of any kind. Also, as others mentioned an air leak, check all hoses, clamps for splits/breaks.


You say it seems like the engine is running under a load, air restriction would demonstrate that symptom and you would probably be smoking oil smoke (are you certain the fuel in the exhaust is fuel and not oil?).


Turbo would get attention from me too, wiggle the shafts and make sure no play and that they spin freely.


One question I would ask as well, are you sure you have the right injectors installed? Was the engine running properly at one time (that you are certain of) with the existing injectors? Or did you buy the boat already smoking? Lots of bubba's just throw injectors they have on hand in these things. You want to make absolutely certain the injectors are correct and the timing and height of them is correct for your exact engine. You cannot go by detroit manual on this as many of the marine builders changed the engines from their original specs.
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