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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

ONAN JB 7.5 new life


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  #1  
Old 03-08-2017, 11:33:25 PM
fisherman81654 fisherman81654 is offline
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Default ONAN JB 7.5 new life

ONAN JB 7.5/3CR8389AD Serial no. G830670481
I found this gem on craigslist, told my neighbor about it and WE felt WE had to get it and I'm glad WE did!

The seller (a very nice person) came down on the asking price of eight hundred to six hundred seventy five. He had bought this unit off of government deals site planning to get it up and use it for his home, He was just too busy and never did.

Its origin was in a North Carolina town called Morganton it was used for some part of the city.

This unit has been well maintained.

We left at six am, drove for three and half hours, bought and loaded it, Got back here and unloaded it about four thirty this evening.

I did stop on the way back and got a few parts so I could hook it up to run on gasoline, it was mostly used to run on propane. The plugs also verified this.


Started going through it from four thirty till eight thirty this evening.
Bore scope in the heads, looked pretty good, cleaned and regaped plugs, checked out plug wires, cleaned glass bowl with lacquer thinner, cleaned battery connections, plugged off propane port on the carburetor then realized it has a large flathead screw that works as a shutoff valve. Then I installed the brass fitting and fuel line on the carburetorhttps://www.youtube.com/watch?v=8fujcKvFzwM. Put some oil down each plug hole.

I said to my buddy, Lets see what this thing has, put the compression gauge in and cranked it.140 steady and holding BOTH sides and a nice spark.
Plugs back in, wires back on, fuel on and hoping the fuel pump does its job.

It did. and it started right up. I had to adjust the carburetor a little as you will see in the video has a slight miss.It doesn't anymore. And the oil pressure is a steady 40 pounds after we ran it awhile. The oil looks new.

Only had power on one leg, We reconfigured that and it worked perfectly.

I probably left something out, it's been a long day, But a GOOD day indeed!

The only thing I still need to do at this point is Take the heads off and I figure it wouldn't hurt to set the valve clearance's. I need to re torque the bolts anyway, it has a very slight leak of oil. I anyone one has data sheets on this unit I sure would appreciate it! I looked on the twain site ,still was sure what to go with. There something about these ONANS.
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  #2  
Old 03-08-2017, 11:36:35 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

ONAN JB 7.5/3CR8389AD Serial no. G830670481
I found this gem on craigslist, told my neighbor about it and WE felt WE had to get it and I'm glad WE did!

More picks
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  #3  
Old 03-09-2017, 12:35:43 AM
nothingbutdarts nothingbutdarts is offline
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Default Re: ONAN JB 7.5 new life

Very NICE!!!!!! You can see the old crud in the fuel bowl in your first set of pictures.

That will be a fine machine. None hooked up here but, I have two JB runners, one in the basement and one in the garage and the remenints of a 3rd that looked every bit as clean as yours however the block is junk from the oil pump being frozen (as in condensation and zero temps.) That reminds me, they haven't been started in like a year.

Enjoy.
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Old 03-09-2017, 01:22:26 AM
Ray Lynch Ray Lynch is offline
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Default Re: ONAN JB 7.5 new life

Nice set.
Good luck with it.
Ray
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Old 03-09-2017, 06:20:18 AM
squidtrap squidtrap is offline
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Default Re: ONAN JB 7.5 new life

Very nice set. I could be wrong but do you have the top and side engine tins? I think they must be in place for proper cooling. Also a flex pipe for muffler, you prob. know all of this but just figured i would mention it, Ed
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Old 03-09-2017, 06:51:10 AM
JohnnyC JohnnyC is offline
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Default Re: ONAN JB 7.5 new life

Nice JB and extremely clean. Great video too. Without doubt so far 2017 is the year of the JBs. These things are popping up all over the place.

JohnnyC
New Jersey
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Old 03-09-2017, 07:17:31 AM
Kevin K Kevin K is offline
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Default Re: ONAN JB 7.5 new life

Nice JB! Maybe someday one will show up close to me. They seem to be pretty rare locally.
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Old 03-09-2017, 08:52:29 AM
PopsGarage PopsGarage is offline
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Default Re: ONAN JB 7.5 new life

Good find a great generator..

Bob
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Old 03-09-2017, 10:20:03 AM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

Quote:
Originally Posted by squidtrap View Post
Very nice set. I could be wrong but do you have the top and side engine tins? I think they must be in place for proper cooling. Also a flex pipe for muffler, you prob. know all of this but just figured i would mention it, Ed
(Know all about this) That's funny I only know what I have learned from you guys. Without the valuable information you guys on smokestack have provided, I would be lost.

I don't know about the tins. Anyone have a pic of what this unit is missing?
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Old 03-09-2017, 10:59:16 AM
gnucklehead gnucklehead is offline
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Default Re: ONAN JB 7.5 new life

Nice set for a nice price, I'm sure glad it went to a good home I'm saving up for another diesel..
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Old 03-09-2017, 12:15:29 PM
Leon N. Leon N. is offline
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Default Re: ONAN JB 7.5 new life

Looks like a vacu flow plant. Maybe no tins are missing. Need to see a better picture to make sure.
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Old 03-09-2017, 03:39:12 PM
Utah Onan Utah Onan is offline
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Default Re: ONAN JB 7.5 new life

Awesome SCORE!!! Jealous, so far I have only seen one JB out here by me.
No, your generator is not missing tins. Your video definitely shows that you have a Vacu-Flo cooled genset.
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Old 03-09-2017, 05:49:47 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

Spent about half a day today adjusting valves and torqueing bolts and cleaning on the JB.
I saw an oil leak coming from some place on the fuel pump, Maybe a gasket? Not sure. Posting a picture maybe someone has had this problem before.
Oil is not seeping from the gasket area that is visible maybe on the inside somehow. I haven't taken it off yet, just wanted to get some pointers first.

It actually looks like its seeping out of that hole.
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Old 03-09-2017, 06:09:59 PM
Max Thompson Max Thompson is offline
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Default Re: ONAN JB 7.5 new life

Quote:
Originally Posted by fisherman81654 View Post
Oil is not seeping from the gasket area that is visible maybe on the inside somehow. I haven't taken it off yet, just wanted to get some pointers first.It actually looks like its seeping out of that hole.
That is a pin that the pump pivots on. I have had "some" luck using a punch to expand the ends of the pin to stop the leak. My preferred option is to block off the mech. fuel pump and add an electric fuel pump.
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Old 03-09-2017, 06:54:22 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

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Originally Posted by Max Thompson View Post
That is a pin that the pump pivots on. I have had "some" luck using a punch to expand the ends of the pin to stop the leak. My preferred option is to block off the mech. fuel pump and add an electric fuel pump.
What about applying a little jb weld in that hole for The JB ?
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Old 03-09-2017, 06:58:17 PM
Dale Russell Dale Russell is offline
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Default Re: ONAN JB 7.5 new life

Clean it GOOD with Acetone first. Might work!!!!!!!!!!
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Old 03-09-2017, 07:52:39 PM
fisherman81654 fisherman81654 is offline
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Default Re: ONAN JB 7.5 new life

Before I apply JB weld, does anyone have a parts breakdown picture for my fuel pump?
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Old 03-10-2017, 08:25:15 AM
stretch67 stretch67 is offline
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Default Re: ONAN JB 7.5 new life

Go with what Max says, make a block off plate for that old pump and put and electric pump on her.

If the old pump fails and fills crack case with gasoline that's a bad thing.

Lots of info on what electric pump to use on the forum here.
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Old 03-10-2017, 10:26:41 AM
Leon N. Leon N. is offline
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Default Re: ONAN JB 7.5 new life

I went out and took a picture of my JB fuel pump to see if it was leaking oil. Guess not. JB has been in operation since 1970. You may want to think twice about using an electric fuel pump WRT the mean time between failure (MTBF). Obviously you would want a high quality device.
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Old 03-10-2017, 10:49:24 AM
HBSaunders HBSaunders is offline
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Default Re: ONAN JB 7.5 new life

was about to bid on that one but was hoping to come up with a decent diesel, keeping my eyes open for one closer to home,howard
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