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Onan 7.5 MDJE 3CR/2268AB New Toy


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  #41  
Old 04-16-2017, 11:05:47 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Nice Hemi. Can I have it?

JohnnyC
New Jersey

Ok... what's the hemi going into??
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  #42  
Old 04-16-2017, 11:09:41 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

A SCHOOL BUS... Sick dude huh?
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  #43  
Old 04-16-2017, 11:42:31 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

What don't you like about the carb. choice? I admit, nothing looks better than something like dual quads on a Hemi but, with the shitty gas these days and the accuracy you can get with fuel injection if I had the funds I would have fuel injection on all my older carbureted vehicles.
Sweet looking HEMI!

Oh yea, Awesome helper you have there!!!
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  #44  
Old 04-17-2017, 05:00:27 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Not having an issue with FI, just 670 cfm...
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  #45  
Old 04-18-2017, 12:01:49 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Well, my Girl is worried about the fuel leak... A bit worried about me blowing up or some such silliness. Sooo, I guess I'm looking for a diaphragm/kit/pump - other than epay any good ideas were to look? Electric wouldn't break my heart at all.

Looking closer at my VR, I noticed my V4 connection is correct (V1-V4) - guess I'm blinder than I remember. I mis-read the terminal numbering. I would like to add an external voltage adjust pot, but all I've got in my stash is 1K pots in that size (1/8" shaft). I'm thinking a 680 or 810 ohm resistor on each end of the 1K pot would work. Accepting, of course, it would narrow the adjustment range a bit. A temporary measure until I source a correct unit.

I've decided to do the 60 A ammeter swap as I'm adding a 50 A Denso 1 wire alt. Interesting side note : original ammeter is a Faria also... I'm not gonna change the glow power wiring, but am going to add an adjustable TDR in via a switch change ( (on)-off-on instead of (on)-none-on) to the control circuit. This will give me the option of manual / off / TDR glow. I'll move the start/remote glow wire to the center terminal of the glow switch. I've already pulled some sealed Mil-spec switches out of my stash, changing both. Going to add a voltmeter also.

Yep, my Girl is awesome! Loves to putter in the shop (even when I'm not there...), great cook, crack shot, and a little hottie to boot! She's started hunting for an Onan to do herself. Competition is one thing, but in my own house?? I offered up a 4CCK I've got buried to her to cut her teeth on, she's thinking on it.
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  #46  
Old 04-18-2017, 11:52:02 AM
len k len k is online now
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

I assume reg is same as on JB.

On JB reg the external voltage pot is 2.5k and goes between pins 1 and 3 ( not V1 and V3).
But if you put your ~ 1k external pot between pins 1 and 2 then, you can take advantage of the existing 1.24k resistor ( R6) on the board and it'll likely be close enough to 2.5k. Besides you can tweak the onboard voltage pot R26 to make up the difference. ( the external and on board voltage pots are in series)

Overall I wouldn't bother adding an external pot, it's just one more item and wiring to fail. Besides given that the voltage reg is self regulating, I don't think you'll need to re-adjust the voltage for 10-20 years ( till reg components start to age and drift in valve). Other problem with adding an external pot is you can accidentally bump the knob and change the voltage.

Last edited by len k; 04-18-2017 at 12:25:56 PM.
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  #47  
Old 04-19-2017, 03:04:47 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Great catch Len, thx! That'll do just fine till I get the correct part. I found some 3 turn 2.5K pots on a surplus site for $2.50/ea, building an order right now to justify shipping. Unfortunately they are full size pots, oh well...
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  #48  
Old 04-19-2017, 11:08:05 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

I stopped by Lowe's and picked up this fitting - 1 1/4 MPT x 1.5" barb. I think it may work ok to transition from the exhaust manifold to 1.5" flex pipe. Barb to flex interface is a smidge loose, I'm thinking mill the barbs down a bit and press it into a short piece of 1.5" exhaust pipe then slide the whole assembly into the flex and clamp. Then I can temp a muffler on it.

I pulled parts to build a temporary outlet box for testing, working on a more permanent design. I've started rounding up outlets for it, so far: a pair of 20amp commercial grade duplex outlets, 120V 30amp twistloc, 120/240 30amp twistloc, and a 14-50 have fallen into the new parts bin (a rapidly filling front belt guard...). Working on metering pkgs for generator and engine. I'm debating a cheap V/A meter for the output of the VR, a few bucks + 1/2hr of time.
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  #49  
Old 04-20-2017, 12:50:38 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

You can get some real cheap V A Kw meters from our good friends across the ocean. I think I paid about $10 for one which reads up to 22Kw. Quality is every bit as good as you might expect but it does serve the purpose. https://www.aliexpress.com/item/AC-V...e-17229452d5cf Cheers Dan
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Old 04-20-2017, 11:37:13 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Good idea to have some type of current monitor on both hots. Just to make sure your near winding amp limit.
Won't hurt to be able to monitor voltage for any problems too.
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  #51  
Old 04-20-2017, 09:51:41 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Dang, you are just slaying this build! Wish I had the time and the resources....
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  #52  
Old 04-20-2017, 11:30:57 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Dan/Len, looking at similar meters on Amazon. The trick seems to be finding meters that have similar appearance/size, takes some digging. The multi function meters are cool, cheap enough to buy a few extras.

Thx TLB01, doin what I can... I'm picking away at it when time/energy permits, having a decent parts stash helps a bit. I got no good ideas for the exhaust yet. I'm debating throwing it on a cheap Horror Fraught trailer with some sort of doghouse.

Quicky count says I've spent about $180 so far, not counting what I've pulled from my stash. Thinking I've invested maybe 6 hrs so far, sometimes in literally 5-10 minute chunks. I still need to assemble a notebook on this project, keep track of time/materials.

Thx a bunch to everybody who has helped on this, and for a LOT of motivation! Still have a long way to go, it'll get there! I still have yet to paint the cart for my NH and bend up/finish out the exhaust on it. Funny how priorities change...
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  #53  
Old 04-20-2017, 11:34:55 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Quote:
Originally Posted by PnishrPW View Post
Funny how priorities change...
Heck of a lot of truth to this statement!!!!
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  #54  
Old 04-21-2017, 12:54:37 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

For testing my JB I just went to couple muffler shops and asked to rummage thru their scrap metal pile. I picked up 3-4 small mufflers from each of 2 shops and just tried them. They looked in almost new condition. Must be kids with small cars removing stock mufflers to put on noisy ones. But if you want a quite one I would avoid the cherry bombs, (ones you can look straight thru)

If I met a little resistance from the guy I offered them a couple bucks (~ $3-4 total). That's more than what they would get at the steel yard..... after they paid a guy ~ $10 to drive it there (net loss).
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Old 04-22-2017, 01:58:06 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

But Len, cherry b's work AWESOME and are super quiet - if you run them backwards... Seriously though, gonna try a Walker 17903 on it - they seem to work good on most smaller gens. Need to get a stack flapper, it's not quite a proper Diesel without one.
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Old 04-23-2017, 03:03:37 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Thx Dan ( BigBlockChev) for the belt info, I ended up going next size shorter which put me right about in the middle of the slots. I bought a cheap $5 belt, I figure it will chew the rust off the pulleys as well as a $21 Gates... Plus I'll need a different belt for the alternator install so I'll pop for a premium belt then.

Now for some radiator news: the solution was literally staring me right in the face! Sitting on a shelf round about eye level - a spare Jeep A/C core. Right about the same size as my fan, mounting tabs on fan land on mounting flange of the core. Just thinking about what I should use to flush it? I'm debating silicon hoses, worth the extra cost?

Not much news on the alternator front. Had the alternator already built on the shelf (4 actually...), wire/terminals/ammeter as well. Haven't had time to hunt up a pulley yet. Also need to hit the wrecking yard for a slider arm, a spacer and pigtail (so I can have a charge light).

I ordered 15 12 volt led panel warning lights (3 pks of 5 to get the colors I needed, wth - they're cheap riiigght?). So they come in and ALL 3 ambers are DOA, ya rolls the dice ya takes ya chances! Messaged Amazon and within 1hr had a response from both Amazon and the seller, 3 new kits coming Monday. Right on! On the up side - nice looking, great color, good luminosity. Will put up some pix soon.

Sorry, no test runs today. Did get a quick & dirty outlet box on it so I can load it some on the next run. Having the water pump hooked up I can run it a bit longer.
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  #57  
Old 04-23-2017, 06:11:17 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

AC core wont have much flow capability with such small long tubes. I would try it but don't get too committed to it until you see whether it has enough cooling capacity. To do that put a temp guage on the line into the rad. Start the engine and put full load on the gen and watch the temperature going in. Leave the cooling fan off until the temp reaches 180 F or so then turn the fan on. The temp should drop in a couple of mins to 150 or below. If it continues to rise or stays the same the rad/fan does not have enough capacity, you have no safety margin. Cheers Dan
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Old 04-23-2017, 10:40:30 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Car water radiators usually are one pass tubes, AC rads are usually many many passes back and forth.

Likely water flow rate will be low with an AC rad, just a couple long tubes, unless you want to re-plumb the ends.
VS water rad with many many parallel tubes for high water flow rate.
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Old 04-24-2017, 01:18:31 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Thx Dan, I was actually concerned about the delta T of the core - being basically 5 rows deep. This is a dual (parallel) circuit unit. I look at it this way: I'm pretty sure I'm going to use the $3.75 fan in any event, the hoses I'll need anyway and the core was free. The testing protocol you propose seems entirely logical, I'll definitely use it. As to flow rate, small line is still bigger than ID of some of the stock fittings. I think I'm ok there. Bottom line, if it doesn't work AND I don't cook the engine I haven't lost much. I had been thinking about using that core as an aftercooler for my compressor. Still one more sitting on the shelf, I've built and parted quite a few XJ Cherokees/ZJ Grands over the years, that's what they're from.

Looking for a good place to locate a water temp sensor ( and probably an oil temp also, 1 sensor, 1 wire and 1 small switch - why not?). I'm thinking between block and pump inlet. Ditto for the radiator. Still looking for opinions on running the exhaust dry, it'll drastically reduce my cooling requirements unless/until I use it for heating. As far as I can tell these use a 150° t-stat, what would be considered a normal/optimal running temp? What would be considered over heat temp? I remember seeing a chart of switch PN vs temp, but I can't find it now.

Got a little bit of time to tinker today and snap some pix. First is some of the indicators and K12 upgrade relays l bought, would've liked oem style jewels but hard/spendy to locate especially in other than red. Minus the defective amber units, I think they're somewhere in the neighborhood of the round file... Relay sockets haven't arrived yet.

Second is the belt I installed, with specs. Cheap $5 pulley scrubber.

Third, belt installed - but seems to ride high in the sheeves, especially the crank pulley. Is this normal?

Fourth, the ammeter that's going in, Faria - just like oem. Got lucky, it was buried in my misc auto electrical drawer. Brand spanking new, no idea how long it's been hanging around or even where it came from. I sometimes think stuff appears out of thin air, more likely my CRS is worsening...

Didn't start it today, almost ready to do a short load test. I want to get it warmed up good then change oil/filters. I've got all new Baldwin filters, just have to grab oil.

Seem to be having technical difficulties uploading porn, please stay tuned...
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Old 04-24-2017, 01:27:00 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Think I got it...
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