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Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke


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  #1  
Old 01-02-2018, 03:36:54 PM
sscummins sscummins is offline
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Default Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Hello everyone here at smoke stac, good to be here again .

Ive had some issues with my onan and she is getting closer but i cant seem to beat this whits smoke when she runs. Its also using an aweful lot of fuel as well. When running after hard starting, it uses about 2 cups of fuel in about 5 minutes and also burns very hot, with the 4 and 2 cylinder exhaust wet with unburned fuel after shutting her down and pulling exhaust manifold.1 and 3 are dry and black. Here are a few things i have checked so far, pulled 4 cyl injector and swapped it with 3, wetness did not follow injector swap. Timing lines up with the flywheel and the pin hole on side of inj pump. Compression in all as follows,#1 278lbs, #2 210, #3 260, #4 260lbs. The inj pump and inj were just rebiuld from a shop in orlando fl.(accurate diesel). $385 bucks ago. Can anyone help with a further diagnose? New head gaskets also, i dont know much on the history, the guy i bought from had it 3 years and guy before said it had blown head gasket. Inj pump pin was broke when i had rebiuld. Any help please is appreciated.

OH I forgot to add the glow plugs all but one check out good. not that this would add to smoke, maybe harder starting ,,,,
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Old 01-02-2018, 03:51:39 PM
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Default Re: 12mdjc-3r/2268d serial #16c859299 white smoke

A crack in a head letting A/F get in the cylinder, cam lobes worn, totally positive the injector lines are on the correct cylinders?

Just because the pump was rebuilt does not always mean it is correct.
Diesels only need heat (from compression), clean air and atomized fuel to fire. Hopefully the smart guys will be along with better answers.


Pump timing could greatly effect starting, temp. and consumption.

Last edited by nothingbutdarts; 01-02-2018 at 05:35:46 PM. Reason: added info.
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Old 01-02-2018, 06:33:54 PM
sscummins sscummins is offline
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Default Re: 12mdjc-3r/2268d serial #16c859299 white smoke

Forgot to mention also, when I was replacing head gaskets, I brought them to heads up here in auburn wa. and they checked for worp and magnifluxed them and they were both good to go. thanks for your feedback.

it sounds as if all are firing, I will get it running here in a couple of days when I have time and crack the line on 4 to see if it lets up on smoke,

does anyone know the direction the pump turns aso I can check to see if all the lines are on correctly? It seems very hard to cross any of those lines the way they are curved and all. Iam not doubting it, I want to verify all of your thoughts. thanks again
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Old 01-02-2018, 06:45:16 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Are you sure it is properly timed. They will smoke if even if a tooth off. Request a manual it has the timing steps. It is a pain to do but must be done.
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Old 01-02-2018, 06:58:32 PM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

i AM PRETTY SURE, i AM SITTING AT PC WHICH IS JUST ABOUNT AN INCH ON FLYWHEEL BEFORE TC STAMP ON IT. AND THE PUMP IS SITTING WITH THE PIN HOLE LINED UP. THAT PIN HOLE IS THE ONE WHERE YOU TAKE OUT THE SCREW ON THE SIDE OF THE INJ PUMP TO REMOVE SO IT WONT TURN. DOES THAT MAKE SENSE? MAYBE THERE IS A BETTER WAY OR THIS WAY IS INCORRECT? ANYBODY KNOW HOW CORRECTLY TO CHECK THE TIMING?
THANKS

Oh yeah and it smells like it to,
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Old 01-02-2018, 08:15:15 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Yes, timing could be off, what I don't get though is why 2 cylinders seem to be firing and 2 are not per the smoky wet cylinders he said yet, compression on #4 looks to be good and it is one that is wet.
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Old 01-02-2018, 05:32:52 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Quote:
...about 2 cups of fuel in about 5 minutes and also burns very hot...
I bet it does, that is 1.5 gallons per hour, about 50% more than full load consumption should be.
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Old 01-02-2018, 05:55:37 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

You may need to pull the injection pump, take it to a qualified shop and have the calibration checked. I would also check your engine oil too as you are probably getting fuel dilution of the oil.
Are the "Wet" cylinders firing at all? Can you barely crack the lines on the cylinders in question and have the engine smooth out by letting off some of the fuel?
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Old 01-02-2018, 06:02:52 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Right now the more you run it the quicker you wash the rings out.ie #2 pressure drop. White smoke could be coolant But in your case already questioning head gasket pull head for heated pressure test at quality not rinky dink machine shop. then have all 4 injectors redone to spec. then clean fuel tank of most likely moisture.
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Old 01-02-2018, 06:49:19 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

White smoke from a Diesel engine indicates unburned fuel.
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