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Onan Generators

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


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  #61  
Old 01-24-2018, 09:51:59 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Where do I start,
I took apart the cap nut which turned out to be 1 pc. with threads into the valve holder (i think), the valve holder is slotted for removal, I made a wrench out of an old socket and twisted it out, that gave me access to the valve which looks exactly like a needle seat for a mikuni carb on my snowmobile. after that coming out I dont see any clip or ring holding in the button. This setup on this pump looks nothing like the manual? I will upload pics of the parts and the pump after partial disassemble.
Any Gurru's have any knowledge, maybe this is an older pump???
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  #62  
Old 01-24-2018, 10:47:46 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

pics 1,2,3,4 more to come in a minute
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  #63  
Old 01-24-2018, 10:49:04 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

5,6,7,8 one more to go
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  #64  
Old 01-24-2018, 10:50:52 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

last one.
I will see what anyone has to say? I am at a loss here now
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  #65  
Old 01-24-2018, 11:04:41 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

ok pic 1 is tag on pump, pic 2 is pump with all of guts pulled like pic 5, pic 3 is what was pulled but together as if it was in the pump, pic 4 and 5 are all pieces pulled seperated partial and completely, pic 6 is same as pic 3 just upside down, pic 7 is spring length, pic 8 is cap nut with spring inside of it, pic 9 is pump emptied without pic 5 in it?

Tell me if I am wrong but these parts do not look very much like pic # 10 which is from manual ,,, Pic 10 hasnt been recieved yet to my email to upload, I will post here shortly page 48 with fig 49 late models and fig 50 early models. is it possible that they had an earlier model???

Please advise,

Steve
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  #66  
Old 01-24-2018, 11:37:34 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Pic 10 is manual 974-0750 page 48...
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  #67  
Old 01-24-2018, 08:03:11 PM
moteurdelco moteurdelco is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

the timing ''button'' is under the tappet(actuated by the camshaft);on the other side of the pump. no need to remove all these parts.
after reassambly and good timing,you will probably need to remove the pistons and find worns rings and valves!.
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  #68  
Old 01-24-2018, 08:34:53 PM
zuhnc zuhnc is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

But, one has to remove all these parts to flow time the pump. And, then put all of them back in, with the exception of the delivery valve spring. Once you know exactly how much your timing is advanced or retarded (see others' posts on this, and the service manual), then you remove the pump, change the button, and recheck. Once your timing is dead on, remove all these parts (again!), and then reinstall all of them (again!), including the delivery valve spring. Once in time, it doesn't have to be done again, until you have accumulated many, many, many hours on the unit, due to wear, or unless something breaks. All of this can be done in a couple of hours, unless you don't have any buttons and have to order or borrow a selection Your pump appears to be one of the earliest models, but servicing and timing is essentially the same. Be clean in removing and reinstalling any lines and parts - dirt is THE enemy of fuel injection pumps zuhnc
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  #69  
Old 01-25-2018, 10:10:17 AM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

Thanks zuhnc, I do know the offness of the button thickness, I did the flow timing test and it is late by 5/8" (.625 ) x.03=0.01875 of a button thicker. And If i understand this all correctly, if my current button thickness is .104 (code 11 or std. p/n#147-0761) then I will need to change current button with a 12 or M p/n 147-0190 correct? and is this alot for the timing to be off? I guess not if someone just rebuilt it, who knows what he did or what wear I have on this thing.
now why would i put together and re take apart and put together again? are you talking about the button side of the pump parts to be removed and reinstalled or the cap nut side parts removed and reinstalled? why?

Please advise,

Thanks again everyone
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  #70  
Old 01-25-2018, 01:37:29 PM
sscummins sscummins is offline
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Default Re: Onan 12MDJC-3R/2268D Serial #16c859299 White Smoke

i re read your post and you mean remove the cap nut and install the spring right?
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