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


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  #41  
Old 01-08-2018, 04:09:03 PM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Here are a couple pics of quantity of smoke FYI
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  #42  
Old 01-08-2018, 04:12:15 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

For the last time. Set the timing by the flow method. It will give you the correct timing.
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  #43  
Old 01-08-2018, 05:26:35 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

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Originally Posted by sscummins View Post
Here are a couple pics of quantity of smoke FYI
You could use that for Mosquito abatement ....... until the tree huggers caught up with you.
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Old 01-08-2018, 06:30:33 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Agreed; use flow timing on the PSU pump. It would probably be a good idea to remove the injection pump and verify that the cam lobe is down and toward you at the PC mark on the flywheel. At this time you can verify that the shim pack thickness is as stamped on the block, and the o-ring seal is on the pump body where it meets the block. Put the pin in the pump side and secure the pump. Follow the flow timing method (after removing the delivery valve, and then calculate the required button thickness per the instructions in the manual. Remove pump and change button, and then do it all over again to verify results. Once you are ABSOLUTELY certain the pump is timed right - follow the manual - then your smoking issue is most likely low compression due to leaking valves or worn rings/cylinder. Set valves cold, remove ALL injectors and then check compression. A very tiny air leak will give you erroneous results. Disconnect the governor link to the fuel pump to "disable" the injection pump. zuhnc
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  #45  
Old 01-08-2018, 07:09:42 PM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

No worries Billy, I am at work and I cant just jump on it doing the flow timing, besides I am not familiar with this and trying get as much knowledge from everyone kind enough to help with their knowledge. Sorry if my lack of knowledge and desire to know more gets people on edge.

Thanks everyone, I will do the flow test when I get the time, I will keep all posted when done.

Thanks again for all of everones help. have a good night.

Steve
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Old 01-08-2018, 07:21:28 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Just reading over this entire thread the initial post really just stood out to me. If you are confident in the compression numbers then that is what I would expect the problem to be. Every IDI diesel I have ever worked on the minimum compression numbers are normally going to be closer to 400...

I'm really surprised you can even get it to start with those numbers.
Definitely check/correct the timing via the flow method until you are confident that it is dead on, but I fear you may find that compression is the issue if those numbers are accurate.

Jimmy
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Old 01-08-2018, 07:50:14 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

I concur; indirect injection pressure should be no less than 350 or so. I see from post #18, your highest pressure is 278, and lowest is 210. That is too great a variance. Also, you have the PSU 4-cylinder injection pump and you must flow time it. (easier for us "hobby" mechanics) The "air timing" procedure is only for the 2 cylinder Brice-Kiki pump. You should do a leakdown test with the proper equipment. Set and check valve clearance first. The leakdown test will tell you where the problem is - rings or valves. If ether has been used, probably broken rings or pistons. My 1968 MDJB has about 400 psi on both cylinders; one has new rings, the other has used rings. Starts easily after the requisite preheat, and has no black or white smoke at any load. zuhnc
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  #48  
Old 01-08-2018, 09:25:33 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Quote:
Originally Posted by alco539 View Post
Just reading over this entire thread the initial post really just stood out to me. If you are confident in the compression numbers then that is what I would expect the problem to be. Every IDI diesel I have ever worked on the minimum compression numbers are normally going to be closer to 400...

I'm really surprised you can even get it to start with those numbers.
Definitely check/correct the timing via the flow method until you are confident that it is dead on, but I fear you may find that compression is the issue if those numbers are accurate.

Jimmy
I had the early VW non turbo diesels and the compression on it was around 460 psi cold. Now the older Mercedes diesels would start and run well with the compression in the low to mid 300 psi range. 210 is way too low with normal starting RPM.
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Old 01-08-2018, 10:56:10 PM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

I have seen J series diesels with numbers in the 250~275 psi range work fine. The amount of smoke and to some extent the rapid heating up of the engine suggest that it is not a compression issue to me . I have also measured other diesels like Westerbeke with compression in the 550 psi range. If the injectors arenít stuck open or set way too low then I am still thinking the timing is off by a significant amount. Cheers Dan
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Old 01-09-2018, 09:18:18 AM
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Thanks everyone, I really appreciate that everyone is so helpful, dont know how I would go about it without ??????, I will check the timing by flow method asap. I regred that it probably wont happen for another 2 weeks, with work doing 12+hrs vacation coverage and leaving for a week next week, I know wah wah wah. LOL I should get back at it full force after I get back following next week.
Thanks again to all

Steve
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