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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan MEP002A


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  #1  
Old 10-18-2004, 07:35 AM
purple
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Default Onan MEP002A

I just purchased this military light plant and have a lot of questions. It has 2 cylinder air cooled diesel. First question is where can I find manuals or more info on this unit? Second question is it sounds like a loud piston slap especially at start up then quiets down a little. Is this normal for this motor? This is a 5KW unit. Is there any advantage to coverting the 3 phse portion of the generator to single phase? Lastly, any idea on where to get parts? Thanks
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  #2  
Old 10-18-2004, 09:33 AM
Kent Redd
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Default Re: Onan MEP002A

If you are not familiar with the detonation that makes a deisel run it my sound like piston slap.

Check saturnsurplus.com for parts.

Kent
  #3  
Old 10-18-2004, 12:25 PM
RAYMOND
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Default Re: Onan MEP002A

I also just purchased one. It is an Onan DJB,or DJE I'm not sure which engine. They're the same except the DJB is 60 cu.in. and the DJE is 70 Cu. in. The Onan Engine manual for the J series should cover the engine, and the electrics is simple enough to handle with the diagram on the top of the control panel. Engine parts are sold by the Cummins Onan Group. The knocking is as Kent said. It is caused by delayed ignition and dissappears under load and when fully warmed up. These units are built with oversize generators giving full output at any configuration. There is no benefit to converting the three phase because it already puts out all the engine can do at single phase. Just flip the switch to what you need and blast the darkness away.
  #4  
Old 10-19-2004, 11:02 AM
purple
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Default Re: Onan MEP002A

Thanks so much Ray for the info. I suspect I got ripped off on mine. What did you have to give for yours? I plan to take the gen off the trailer, mount it on a concrete pad behind my garage, enclose it in a sound deadening box, put and exhaust fan on the box, route the exhuast pipe out the top, wire it into my panel with a cutoff switch and be ready for the next hurricane season. I then plan to build a motorcycle trailer from the gen trailer. Someone told me these units are really under rated as far as KW goes. Can you explain the 7.2/5KW rating? I suspect the 7.2 might be the 3-phase portion of the generator. If so, it seems to me converting the 3-phase to single phase may get me more power. Is my logic flawed?
  #5  
Old 10-19-2004, 01:16 PM
MDmike
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Default your question on dual output ratings

The dual output rating are

7.5 kw surge (max output) 5 kw continous output

hope this helped
  #6  
Old 10-19-2004, 01:19 PM
purple
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Default Re: your question on dual output ratings

Thanks. That is the way it worked on my little gas generator but I wasn't sure about this unit as it has both a single and three phase output.
  #7  
Old 10-19-2004, 01:23 PM
RAYMOND
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Default Re: Onan MEP002A

The KW rating is usually limited by the engines power rating. With normal 3 phase generators, there is usually a 25 percent excess of copper and iron to allow the extra reactive current for motor operation, and some additional starting current. After all the reason 3 phase power is used is mainly for motors. Normally operating one of these single phase at the same voltage requires derating by 1.732 of the kva maximum current; the limit being coil current. By reconnecting the coils in double-delta, or low zig zag, the voltage becomes 120/240 and the coils limit the output to 66% of name plate rating. To make full use of the engine, our uncle having unlimited recources has wound his genetators with 50% larger coils than normally required, and thereby allowing full KW output on single phase operation. This also requires 50%extra exciter capacity. Hence the 52 amp at 120 volt capability of your machine. The military under rates their engines at least 20% but I'm not sure if the fuel is cut back. You can tell by loading it until the frequency begins to fall rapidly with load addition and the fuel arm is against the stop. If it belches black it is full fuel, if none or very light smoke, it is set back and you can set it up by adjusting the fuel stop screw. This same unit is rated a 6 Kw Civy. I dont believe given the oversize windings that you can hurt one of these units other than the obvious short circuit or low speed operation. These units also use magnetic amplifier exciter field power so they will start motors very well. But you must be carefull about under frequency operation. The high current combined with reduced cooling can overheat the windings, the field has a breaker so it should be OK. In answer to your question, there would be no benefit to any electrical chances in this machine.
  #8  
Old 10-19-2004, 01:44 PM
purple
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Default Re: Onan MEP002A

OK I got you and thanks Ray. I just read an article some where on the WEB that said the 7.2/5KW rating meant it was rated at 7.2 normal altitude and 5KW at high altitude. Less air less power. I think I saw it on some surplus site. They were describing what the two numbers meant.
  #9  
Old 10-19-2004, 10:56 PM
RAYMOND
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Default Re: your question on dual output ratings

I just load tested mine and I couldn't make it smoke at all ever, and it was slow coming up to speed. It took six turns out on the max fuel stop to get any smoke, and now it responds considerably faster. For some reason some army dude thought setting down the fuel stop would help something; and maybe it had something to do with the governor droop set way up. The frequency meter didn't work and the full speed setting was dam near 90 cycles. When I got it all straight, the droop looks to be about 5% and the max speed is around 64 cycles. (a personal preference)The frequency meter had a broken wire at the input connection. Runs like new now.
  #10  
Old 10-20-2004, 04:01 AM
robert martin
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Default regerlator

I have a 1968 milt. onan geneator that john r. hollinsworth co s#13423 reglator. I lost power from 220 v to 50v geneator is a 3 kw. would like to know if any one could help or tell where i might get one. geneator was rebilt in 1988 an only has 30 hrs. would appr. any info i could get thanking you verry much plese reply bobby martin tambob 33597 @ msn.com
  #11  
Old 10-20-2004, 06:43 AM
purple
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Default Re: your question on dual output ratings

I played with mine a little last night also. The guy I bought it from had it running wide open. I adjusted the governor rod (at the fork) a little and now it runs slower but I don't really know how to adjust it properly. The linkage that goes down to the inject pump is broken at the plastic tip but stays on. Maybe some JB weld will hold the plastic. I have searched everywhere looking for an adjustment procedure but can't find it. Going down at lunch to get the oil filter. Drained the oil and removed the oil filter last night. I need to find a 30 volt meter and a master switch. Mine was replaced by just a toggle switch. I love my new toy.
  #12  
Old 10-21-2004, 12:04 AM
RAYMOND
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Default Re: your question on dual output ratings

All that info is in the Onan J series engine manual.
  #13  
Old 10-21-2004, 08:26 AM
purple
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Default Re: your question on dual output ratings

Where did you find the manual Ray?
  #14  
Old 10-21-2004, 11:40 AM
RAYMOND
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Default Re: your question on dual output ratings

I believe I got it from the Onan dealer, or maybe from one of the websites that deal with Onans.I have all three books, The J series engines, the YD generators, and a DJE parts list. This unit doesn't use the YD generator. It's one of the military standard units. It is 3 times larger than the YD equivalent by Onan. When in doubt about the frequency you can rely on one of those old motor driven clocks. They use a synchronous motor which will follow the generator output cycle for cycle.
  #15  
Old 10-22-2004, 05:10 AM
Jim Lane
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Default Re: Onan MEP002A

ONAN ENGINE MANUALS.. If you are looking for engine manuals for the DJB engine for your MEP-002A, I was able to find a lot of ONAN engine parts manuals at the below site, it is there about 1/2 way down. They have manuals for RV gensets, marine gensets as well as the engine manuals.They are all in PDF. They also seem to be for the civillian version but the militarized version only seems to be a change in the 24 volt for the military/ NATO and the ancillary items like the fuel filters, air filters, control panel, exhaust but that is the easy part. www.donhillmaninc.com (cut & paste to browser) Go to: ONAN Parts Catalog (then) Engines. You can also get the TM from the government website although it is rather intimidating. Good Luck, Jim L.


www.donhillmaninc.com
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