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Onan MDJA 3.0-3CR /2268V


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  #1  
Old 02-06-2017, 01:24:40 PM
Crankpot Crankpot is offline
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Default Onan MDJA 3.0-3CR /2268V

Ive had this for years up at my Tennessee cabin. Brought it home to re ring it as it has many hours and smokes a bit and the head gasket is weeping coolant.

The over temp switch screwed to the cylinder head rusted and broke and the new one is unavailable. I think I found the right replacement. Its an empire R1912 switch. Opens at 250 deg F. like the original. Cost $16 ebay. Thought some of you might find this useful.

I need a head gasket and ring set for this unit and cant find one.. Anybody know of a source. I've tried the usual sources.

Thanks

Bob
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  #2  
Old 02-07-2017, 10:56:24 PM
Crankpot Crankpot is offline
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Default Re: Onan MDJA 3.0-3CR /2268V

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Originally Posted by Crankpot View Post
Ive had this for years up at my Tennessee cabin. Brought it home to re ring it as it has many hours and smokes a bit and the head gasket is weeping coolant.

The over temp switch screwed to the cylinder head rusted and broke and the new one is unavailable. I think I found the right replacement. Its an empire R1912 switch. Opens at 250 deg F. like the original. Cost $16 ebay. Thought some of you might find this useful.

I need a head gasket and ring set for this unit and cant find one.. Anybody know of a source. I've tried the usual sources.

Thanks

Bob

I inspected the breather valve. The inside was clean and the four little balls were moving freely.

Here is a video of the little generator. I'm still looking for a head gasket...

https://youtu.be/iz0qRQ2aucM
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Old 02-10-2017, 10:49:53 PM
Crankpot Crankpot is offline
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Default Re: Onan MDJA 3.0-3CR /2268V

I found a head gasket for $30 and a set of .030" oversize rings also for $30. I will file the rings down to size. It's absurd how expensive parts are for these aging engines are. I saw ring sets for $140 and pistons for $500. I guess someone is paying these amounts or they wouldn't be for sale. The newer Japanese generator engines are looking much better now...
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Old 02-10-2017, 11:13:13 PM
David C David C is offline
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Default Re: Onan MDJA 3.0-3CR /2268V

I haven't looked up what the part number is, but there are some .010" over rings on eBay that may be a DJ series engine. I personally would not file down .030" rings for use in a standard bore. I would thing the extra ring tension would be a little hard on the cylinder bore, plus the fit to the bore may not be the best.

http://www.ebay.com/itm/CUMMINS-ONAN...FVCbsO&vxp=mtr

David C.
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Old 02-25-2017, 06:37:48 PM
Crankpot Crankpot is offline
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Default Re: Onan MDJA 3.0-3CR /2268V

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Originally Posted by David C View Post
I haven't looked up what the part number is, but there are some .010" over rings on eBay that may be a DJ series engine. I personally would not file down .030" rings for use in a standard bore. I would thing the extra ring tension would be a little hard on the cylinder bore, plus the fit to the bore may not be the best.

http://www.ebay.com/itm/CUMMINS-ONAN...FVCbsO&vxp=mtr

David C.

Here I fitted the rings to the old piston. The old rings were badly worn with .060 end gaps. I fitted the new rings to the spec at .015". Also the cylinder bore was nasty . Obviously had rust marks and a tiny ridge at the top. The piston was fine except for the top which was chewed up I think from sea water injestion. Everything else inside the case was pretty. I expect this little guy will run nicely with the new rings and hone job. I should have it running by tomorrow...
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Old 02-26-2017, 09:32:37 PM
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Default Re: Onan MDJA 3.0-3CR /2268V

I worked on it a bit today. Got the oil pan back on after making a new gasket, collected the parts to assemble the head. While putting things together it became apparent by the wear marks on the pushrods that the previous mechanic had installed the pushrods upside down. Anyway they are correct now, and fit nicely.

The rest of it went without issue. I took everyone's advice and applied a layer of kw copper gasket spray to the head gasket. Time will tell if it holds but I feel good. I draw filed the block and head. Both needed help. Both are much better now than before and of course it was seeping coolant. Again time will tell.


I added junk oil to flush out the crud and will change the oil after I get it up to temperature the first time.

It started up easily and settled into a smooth governed idle, but I only ran it a few seconds as my cooling system isn't set up yet, but no major noise, leaks, smoke or other problems.

I'm replacing most of the external wing with new modern stuff as well as added a 20 amp dual marine circuit breaker to the control box.

More coming...
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Old 02-28-2017, 08:16:41 AM
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Default Re: Onan MDJA 3.0-3CR /2268V

I started it up today. It immediately overheated. Oops I hooked up the coolant lines backward duh. I let it cool, corrected my mistake and tried again.

It overheated again. Well at least the new overtemp limit switch works. It's funny because this things cylinder head always ran very hot, like 235 degrees at the head location where the overh switch sits. Been that way for 10 years and I figured its normal. Well....

I disassembled the coolant tank to inspec the thermostat and guess what... I put I together as shown in the parts diagram. Nothing wrong here but it acts like the thermostat is installed backwards. Out of desperation I reverse the thermostat so now the coil spring is down dipping into the hotter coolant and fire it up.... perfection! It warms evenly, cools easily. The max temp I sw was 188deg F with the average coolant temp 160 deg F. I appears its been assembled incorrectly for a decade.

On to break in...
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Old 02-28-2017, 08:32:12 AM
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Default Re: Onan MDJA 3.0-3CR /2268V

I did an oil change and readied the engine for loading but geeeez this thing is loud with no muffler! I need to get the exhaust system done before I can run this for break in periods...the old onan exhaust flange was in bad shape from years of use and the previous exhaust system was a cobbled up collection of parts all of which was failing. Time for help from Charlie (neighbor and retired machinist)...

Im no welder but I have a little miller syncrowave box and get by so here is what happened...

First off I found some suitable exhaust pipe...in this case it was a former directv satellite dish mounting pole! I chopped it into a couple 45's and welded them into a 90. Not the best for high performance flow but it met my needs of making a compact turn to allow the subsequent piping to remain close to the engine.Then Charlie took the old flange and chucked it up into his giant Leblond lathe and cleaned it up so it was an interference fit sliding into the newly made 90 degree exhaust fitting. Then he brazed the two parts together.

It's a work of art now! It will outlive me it's strong and proper.
More coming...
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Old 02-28-2017, 01:07:25 PM
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Talking Re: Onan MDJA 3.0-3CR /2268V

Hope you are smart enough to remember to put a section of Flex Pipe at the engine end of your fancy Exhaust System..... Those DJA's jump around a bit when running......
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Old 02-28-2017, 01:10:07 PM
Crankpot Crankpot is offline
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Default Re: Onan MDJA 3.0-3CR /2268V

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Hope you are smart enough to remember to put a section of Flex Pipe at the engine end of your fancy Exhaust System..... Those DJA's jump around a bit when running......

Lol...I'm not too smart but yes it's getting some flex pipe there!
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