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New Proud Owner of an Onan JC


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  #21  
Old 10-04-2017, 01:54:47 PM
stretch67 stretch67 is offline
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Default Re: New proud owner of a JC

New to me 2014 Chevy Silverado

Dexos 0W20 8.5 Quarts

Full Synthetic

So that has to say something about the new oils
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  #22  
Old 10-05-2017, 11:39:39 AM
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John Newman, Jr. John Newman, Jr. is offline
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Default Re: New proud owner of a JC

Leon:
One side of that diaphragm has never seen anything but air. Could be weakened from being constantly flexed while dry all its life. Maybe not, but I'd at least check it before putting gasoline to it.
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  #23  
Old 10-05-2017, 11:57:50 AM
len k len k is offline
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Default Re: New proud owner of a JC

Even wet fuel pumps can crack the diaphragm. Had a 85 Chevy 305, oil was thin, diaphragm was leaking.
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  #24  
Old 10-05-2017, 12:09:40 PM
Wayne 440 Wayne 440 is online now
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Default Re: New proud owner of a JC

It took me a long time to finally realize how a mechanical diaphragm fuel pump works. When it is dry, the diaphragm flexes a lot more than when the pump is actually filled with fuel and has built up pressure.
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  #25  
Old 10-05-2017, 01:08:59 PM
Leon N. Leon N. is offline
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Default Re: New proud owner of a JC

Things would have to get real bad around here for me to even consider using gasoline. Good comments. Lets hope I never have to resort to gasoline.
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  #26  
Old 10-09-2017, 10:48:03 AM
JT240Z JT240Z is offline
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Default Re: New proud owner of a JC

Good comments indeed. I'll be taking it all in and appreciate the extensive knowledge that's being sent my way. I pick up the unit on Thursday and post some pics. Been unable to pick it up since I've been a little busy at Road Atlanta for the Petit Lemans. Been on Onan NHM power from Tues - Sun without a glitch.

Excited to begin a new project with the JC. Hopefully, it will be a simple return to life for the genset. If all checks out good, I plan on installing a new concrete pad behind the house, constructing a weatherproof housing and running a new NG line to it. Good opportunity to run NG to the kitchen for a gas stove in the future. Currently only use gas for heat. Plan on running a 1" pipe from the meter to the genset and a 3/4" pipe to the kitchen. The gas meter/regulator is about 30' away from the genset's final resting place. Comments?
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  #27  
Old 10-09-2017, 01:45:58 PM
len k len k is offline
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Default Re: New proud owner of a JC

NHM ....... If it's been sitting for few months clean the slip rings before making AC , it stresses the AC votlage reg. In my testing ohms thru the brushes increased from ~ 23 to 100 ohms after 3-5 months of sitting. And running it ~ 1 hour w/o reg only lowered it ~ 10%/ Onan says clean at 30 ohms.
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  #28  
Old 10-09-2017, 02:15:07 PM
JT240Z JT240Z is offline
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Default Re: New proud owner of a JC

Quote:
Originally Posted by len k View Post
NHM ....... If it's been sitting for few months clean the slip rings before making AC , it stresses the AC votlage reg. In my testing ohms thru the brushes increased from ~ 23 to 100 ohms after 3-5 months of sitting. And running it ~ 1 hour w/o reg only lowered it ~ 10%/ Onan says clean at 30 ohms.
Thanks for the advice, but the NHM has been with me for a long time. Run it every 30 days for an hour or more and verify the slip rings every year. Just had the geny out and polished the slip rings to a bright copper finish with a Scotch Bright pad. I understand all too well how those dirty slip rings will destroy a VR. A few years ago I failed to do my monthly service and fired her up and put her under full load. The next time I tried to use it I had no AC output. It ended up costing me a VR. When I checked the resistance of the slip rings it was just over 100 ohms. At $300 a pop, they're not something I like to replace very often. Ever since then, I got into a regular maintenance mode and have never had another issue.
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  #29  
Old 10-09-2017, 02:30:14 PM
len k len k is offline
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Default Re: New proud owner of a JC

I have a NHM, nice thing is unlike NHE types it will run even if it doesn't make AC .

With reg unplugged so it can't make AC, I just run engine and hold a scotchbrite pad under the slip rings. For a holder I cut off the 2 side tines of 4 tines off a kitchen fork, and jabbed strip of scotchbrite on end , and tied other end of strip with cotton string.

PITA to unplug reg so I plan on adding a switch toopen the line from controls to flashing pin 7 of reg, that will prevent stop the boot strap process of gen starting to make AC. Was thinking of putting one of those military type red "Toggle Switch Guard Covers" over it, so it will be obvious that normal position will be cover closed ( switch on)

Last edited by len k; 10-09-2017 at 02:47:31 PM.
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  #30  
Old 10-09-2017, 04:01:20 PM
Jim Marcozzi Jim Marcozzi is offline
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Default Re: New proud owner of a JC

No synthetic oil- not necessary and won't offer any advantage. Stay with something such as a good brand name 5W30 or 5W40. I run Baldwin filters.

Keep a spare regulator handy. The YD's will eventually fail and it's usually when it's really needed and not during an exercise.

Check the lower electrical box for rodent damage and use expandable "fire foam" to fill all voids in the boxes so mickey mouse can't get in and jack things up.

Check/adjust valve lash. Install & gap new plugs. Check over the rest of the ignition secondary. Clean the "run" contacts under the cover. Clean/replace the ignition points and set properly, along with timing.

Load at least 50% rating and when warm, set RPM to 60.2-60.5 Hz. Adjust voltage.

Take the charge resistor out of the YD's cooling duct and bead blast the resistor's exterior and the clamp. They get corroded and you lose 12V charge. Once assembled, run get with a charged battery and set voltage to about 14.0-14.4V at the battery when running.

And importantly.....always remove the air cooling covers several times per year and inspect for mouse nests. They LOVE to build nests around the jugs and other hidden places. Running them with nests will starve the engine of cooling air and cause damage in no time.

With some TLC and PM, the JCs will out last you. And me.
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  #31  
Old 10-09-2017, 05:18:59 PM
JT240Z JT240Z is offline
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Default Re: New proud owner of a JC

Quote:
Originally Posted by MBB View Post
Here is some info on your unit.
How do I know what spec this unit is? The model number doesn't seem to match the information I've seen on how to read it unless it's a spec 'B'.

I think I got my answer on this. According to Cummins, it's a spec AB. Strange that the model number only says B but the build date was confirmed as Dec 1988.
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  #32  
Old 10-09-2017, 05:21:32 PM
MBB MBB is offline
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Default Re: New proud owner of a JC

On the newer models even though it says AB you only read it as Spec B.
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  #33  
Old 10-09-2017, 05:53:15 PM
JT240Z JT240Z is offline
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On the newer models even though it says AB you only read it as Spec B.
In this case, it's actually the opposite. The label says only B but Cummins says it's actually AB.
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  #34  
Old 10-09-2017, 06:04:09 PM
MBB MBB is offline
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Default Re: New proud owner of a JC

No we know because of the date it's an AB . The original would have been much earlier I'm guessing maybe the 60s . They even new better and stamped it correct. Not all are that way.
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  #35  
Old 10-09-2017, 06:42:17 PM
JT240Z JT240Z is offline
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Crazy how things were better earlier on. I figured it was spec AB but needed a confirmation on it. Plan to pick up some known to be needed spares and needed a confirmed spec number to go by. You guys have really been a lot of help. Much appreciated.
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  #36  
Old 10-09-2017, 08:18:23 PM
len k len k is offline
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Default Re: New proud owner of a JC

If it's got a 2 inch tall penthouse on to of control box it's not spec B it's AB.
Seems Onan dropped the leading A some time after they crossed spec AA.
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  #37  
Old 10-10-2017, 05:22:39 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: New proud owner of a JC

My 1980 JC has AB as the spec stamped into the data tag.
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  #38  
Old 10-10-2017, 06:07:32 AM
MBB MBB is offline
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Some as I mentioned are stamped with one letter some with 2. The date is what determines it. They built so many that Onan went through the alphabet
and started over. We just know that an early single letter would be probably a magneciter from 60s 70s and the 80s 90s would be the YD end. I never ordered any parts but when refferencing the model and spec I would give both spec letters to be sure but look at the date to confirm.

I know its clear as mud.???
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  #39  
Old 10-10-2017, 09:56:51 AM
JT240Z JT240Z is offline
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Quote:
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I know its clear as mud.???
As clear as it needs to be.
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  #40  
Old 10-10-2017, 01:06:09 PM
len k len k is offline
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Default Re: New proud owner of a JC

If it's relatively new ~ 1977 the B is AB and it has electronic AC votlage reg ( in 2 inch high penthouse over the control box)

IF it's old ~ 1950 or 1960's and no penthouse then B likely really means B , not AB. And it has magnaciter for ac voltage regulator


They likely dropped the leading A since it may have been incompatable with their internal paper or computer tracking system.

Place I worked at ran into something like that when desktop computers came around for the datebase. Big debate between engineering and manufacturing depts on consolidating the numbering system on drawings. In our company we put a "-0" after drawing number to mean "package dimensional Outline drawing", but for revision numbers we put -1, -2, -3 ......
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