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Onan 7.5 MDJE 3CR/2268AB New Toy


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  #21  
Old 04-09-2017, 05:46:33 PM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Iiiitt llliiiiivvvves!! Gave it some juice and power and it woke up. Actually, I pulled the wire off the fuel solenoid and glow plug relay - then spun it over for a couple of 30 second bursts after priming fuel pump. Oil pressure came right up, (memo to self : damn gauge needs a 45 elbow...). Hooked up glows and fuel solenoid, gave it 60 seconds or so of pre-heat and cranked... and cranked... Took a bit, but it started coughing and white smoke then woke up. Kept the glows on for almost another 60 seconds until it smoothed out. Let it run about 3 min, oil pressure stayed basically pegged. Charging hard on gauge, didn't look at volts, darnit. Was forced to use 4/0 cables, what I had handy. It spun over just dandy!

2nd run several minutes later : hooked up VR and meter on T leads and restarted without glows pretty much instantly. AC volts @ 169! Twiddled pots - no real change. Turned VR way down get about 115. Volts bouncing around a bit - 10 to 15 volt spread, no load. Hovering right around 58.5 hz, pretty even. Ran another 3 min or so pretty much perfectly then I shut it down. Not too warm, I could still hold my hand on block. Field breaker popped near the end of the run, pushed it back in and it stays. Noticed it stops charging if field breaker pops.

The bad... mechanical fuel pump seems to leak. Will investigate shortly.

Overall, pretty happy dude here! Maybe $25 in misc hardware / fittings / hose / PB. Cables / group 49 (or 94??) battery from my stash, ( ok, I stole the battery off my NH...). I need to wire up and test the 4 GC-2 6v batteries I picked up for core charge.

Onto the maintenance stuff now: oil/filters, adj valves etc.

Guess I'm going to need some parts to build this project: Probably should look into an air cleaner set up first, probably should plug the hole in the intake too (or should I swap to a DJB/E intake manifold?). Cooling will be next: I'm thinking dump the exchanger and use a large, common / cheap heater core / fan assembly for now.

I've decided I shouldn't have to hold the pre-heat switch for a minute so I scrounged thru my stash of time delay relays and pulled out a 12v one and a 8 pin socket to install. Need to find one with a knob instead of dip switches and remote the pot to the front panel. Ditto for the V adj pot, simple 2.5 K pot.

More to come...
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  #22  
Old 04-09-2017, 05:53:14 PM
TLB01 TLB01 is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Omron makes really good timer relays if you are looking for the knob style. Plenty of them on fleabay.
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  #23  
Old 04-09-2017, 08:47:36 PM
len k len k is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

I'ld put a sleeve around the knob if on panel. Too easy to accidentally bump knob to full time out. (copper pipe cap maybe)

Did that at work on a audio amp driving a speaker shaker driver I made, watched the magic smoke leave the speaker. Had to replace and rework a new speaker.
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  #24  
Old 04-09-2017, 09:27:02 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Probably need a switch guard on the momentary contact switch if anything. Omron makes 1 minute (max) timer relays and that is about right for an old J series glow time. Hardest part is going to be fabbing a bracket inside the control box so the knob is flush with the outside. That is if you go with Omron. Dunno about the others other there. Omrons don't tend to die. I have pellet stoves that use them and they tend to be the last part to worry about.

---------- Post added at 06:27:02 PM ---------- Previous post was at 06:12:36 PM ----------

Just a heads up...Omron....like Yokogawa...has fallen into the Chinacrap trap. It will be best to shop carefully if you are Chinacrap adverse. All my Omrons were made in Japan in the 80's and are still working today.
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  #25  
Old 04-09-2017, 09:39:36 PM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Just a note to thank everyone for the info and motivation! Going into parts hunting mode now. Thinking about adding some metering, maybe wireless remote start - cause I'm lazy and it's cheap!

Thx Dan, I'm guessing the 11 in the belt # is width and the other is diameter? I'm considering substituting a Denso 50A alt for OEM charging system, mounted in place of raw water pump. I build these on the side as one wire racing alts for a lot of the local racers. Will have to swap ammeter (in my stash) and some wiring also. Looking at the wiring schematic, moving a couple of wires and swapping in a 60-0-60 ammeter, one could easily monitor glow plug current also. Let me know if I develop a glow plug issue.

TLB, your right - Omron is a good vendor.

Curious as to what you all are using for mufflers?
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Old 04-09-2017, 10:11:29 PM
TLB01 TLB01 is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

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Originally Posted by PnishrPW View Post
.

Curious as to what you all are using for mufflers?
So far....nothing. That's finishing details, haha!

2 of my sets have NPT (the MDJC's) so something that works with that. Probably a dumb ole 30 dollar tractor muffler.

The other is going to be some kind of flange, flex pipe and another dumb ole tractor muffler. Its going to depend if the final solution sits in my car port or in the garage with a thimbled exhaust out of the wall. In that case it will be flex, car muffler suspended by raceway/threaded rod etc.

---------- Post added at 07:11:29 PM ---------- Previous post was at 07:01:24 PM ----------

One thing you have to consider is getting rid of that resonator and finding a real air filter. So far for me its been a real PITA. As of right now you have no air filtration at all. On MDKC I ordered a K&N that sticks right on the intake but the MDJ's require either fabrication or finding a stupid elbow for a Donaldson style that is next impossible to find or finding a donor set for the normal air box. You can also use a MEP002a intake in your case if you want to go Donaldson style but you will need some different style hose and mounting for it to work.
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Old 04-09-2017, 10:27:32 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

So, you're the one who snagged the Onan on Craig's List. I have two MDJE 3CR's. One is a 1971 and the other is a 1979, which is in my boat. I was inventorying stuff (I just bought the boat recently) and my spare Onan belt is #511-0067. I don't remember if it's a Gates or what. The 1971 Onan S/N 0571298586 snapped a twig and the previous owner attempted to fix it. He replaced all the gears and some seals only to find out there was something sheared off deep inside, according to the local Onan dealer. (Does anyone know what that could be?) Other than that "thing" that is sheared off and now, some missing parts, the genset was a good runner. Don't know if I am going to part it or what.
Frank
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  #28  
Old 04-09-2017, 11:32:37 PM
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BigBlockChev BigBlockChev is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Timeless , pull the pan and see what comes out or pull the oil fill plate and use a magnet to fish around.
Pnish , anything that fits for a muffler, 1 3/4"inlet clamps reasonably well to 1 1/4 pipe. Some Honda mufflers are just about right. Also a 1 wire alt would be good if you can get em cheap enough. If you are using a 12V fan you will need 10A or so to run it, the stock system will put that out but not much more.
All, I would not put a timer on the glow plugs , 1 min is good when it is cold but unnecessary when warm. You want to be kind to the glow plugs themselves the little buggers are expensive, rare and problematic to get in and out. Use em when you need them only and not otherwise. Cheers Dan
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  #29  
Old 04-10-2017, 09:27:55 AM
Crankpot Crankpot is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

As for your marine conversion, I've had very good luck using residential grundfos brand hot water circulating pumps. They come in 110 V or 230 V versions, love hot pressurized glycol lubricated coolant, and seem to last forever. I've also used the cheapest radiators I can find which come from Honda Gold wing's. You can purchase used ones on eBay, they include a radiator fan, very easy to implement never had a problem with them and they're sized appropriately for your two cylinder diesel gen set. good luck
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Old 04-10-2017, 09:37:33 AM
Crankpot Crankpot is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

This shows my $7 air filter solution. Works great. Next picture shows coolant pump and radiator from 1200cc gold wing. $25.
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Old 04-10-2017, 09:42:40 AM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

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This shows my $7 air filter solution. Works great. Next picture shows coolant pump and radiator from 1200cc gold wing. $25.
Oops...air filter
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Old 04-10-2017, 10:42:38 AM
Ray Lynch Ray Lynch is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Crankpot
Nice looking set up.
Ray
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  #33  
Old 04-11-2017, 02:11:58 AM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Thx for all the great ideas guys!

My exhaust is NPT, looking easier to adapt. Looking for a cheap flex setup now. Is it ok to run a wet manifold dry?

Crankpot, good idea on the air cleaner! I'll be stealing that... Actually, leaning towards plugging the hole, machining top and bottom plates from 1/8" aluminum to fit on top of air horn and use the same air cleaner as my NH's. Very nice MJA!

I've done several MCCK conversions using Taco pumps, only because I get a good deal on them and keep a couple of common ones in stock. Grundfos is a great brand also, would use them in a heartbeat.

Did some shopping today : picked up 4 10" cheap 12v e fans off of Offer Up for $15/all. Looking at a larger Chevy truck heater core for $20/nib. Somewhere I have an small expansion tank. Cooling system is starting to take shape.

Grabbed on of my one wire Denso alternators for a look-see, seems workable. The 5" racing pulley - notta sa much... I had to remove the pulley for the pic, the alt was almost hidden behind it! Going down to my fave alt builder and do a little pulley hunting. I figure I need to turn the alt about 4000rpm to hit max output, little less ok too. Yes, that is a 4/0 battery cable by the alt-it's what I had handy! Actually they are spares/extras for my Trace inverter setup.

Went digging through my gauge bin and found a new Faria 60-0-60 2" ammeter. Next time I'm near it I'll probably do the ammeter mod: swap meter, change 2 wires and remove the copper strap between solenoids. This will let me monitor current on the glows/intake heater. I'll give up some lower gauge resolution, but I'm adding a volt meter so not too heartbroken.

Minor setback... Seems like when I'm charging the battery hard the field breaker trips. Disconnect charging and all seems ok. Did two 4-5 min runs today, one this morning and another after work breaker popped this morning but not after disconnecting charging system. Am I missing some interaction between the 12v charging system and the AC section ??? They look like separate systems on the schematic.
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  #34  
Old 04-11-2017, 06:13:14 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

One nice thing about keeping the water cooled exhaust manifold in the cooling loop is the extra heat for your house and hot water. Since a house typically only loads a generator to a few hundred watts, there won't be a lot of heat available from the water jacket alone. A diesel looses a lot of heat to the exhaust when on light load.
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Old 04-12-2017, 01:23:50 AM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

I was thinking along those lines, but having a bit of trouble wrapping my head around the internal plumbing of the exhaust manifold. I guess it's time to drain the cooling system, disconnect some hoses and see what goes where...

Didn't work on it today, but ordered some (3) 6v 8pin cube relays off Amazon, along with some other misc goodies. I decided to go with the blade style cube because of small footprint, right about the same size as the original.

I'm starting to put together some ideas for the breaker/output box, probably start by raiding my stash and see what pops up. Also looking into metering options, both output and engine sides.

I'm guessing the YD gen ends hold tighter numbers than my NH spec D's do?
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Old 04-16-2017, 09:39:35 PM
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Finally got a chance to work on the new toy. My fiancee came along to help, she built the skate to put it on temporarily. She's always up for a trip out to the shop! I pulled out and wired up the batteries, then got the torched/cracked exhaust manifold and nipple extracted and separated. More next post...
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Old 04-16-2017, 09:47:26 PM
JohnnyC JohnnyC is online now
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Watch out or your "Boss" will know more than you regarding these Onans... That is one big bunch of batteries.

JohnnyC
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Old 04-16-2017, 10:39:06 PM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

My lady then traced and labeled the output leads and did the neutral/ground bar. I hepped, i dug up the parts : a ground bar to cut down and a new set of stainless hardware.

Then I had to test the new battery setup... My Midtronics battery tester says I've got about 1200+ CCA available. Didn't seem to eat much battery on starting, here's gauges after a 5 min run at 60F. Ran my Girl through a cold start, she aced it!

I seem to be developing a leak around the lift pump, diaphragm is moist all the way around and screws, bolts and fittings are tight. More coming...
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Old 04-16-2017, 10:57:56 PM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Yeah, little bit o' juice there. Got em for core charge, using all 4 to keep them fresh.

Ok, a little more porn... I'd like to find another hold down like this one.

Something I noticed, VR has V1-V3 not V1-V4; is this a problem?

Last pic is a little project I'm finishing up for a client, figured y'all might appreciate a peek... Not enthusiastic about his choice of carburation, but motor is mild - should be okay.
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Old 04-16-2017, 11:03:47 PM
PnishrPW PnishrPW is offline
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Default Re: Onan 7.5 MDJE 3CR/2268AB New Toy

Could using V3 instead of V4 be causing my output voltage to swing a bit? I still haven't put a load on it yet.

Another thing: occasionally the motor seems to labor slightly, like a small load has been dropped on gen?
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