Used Onan Quiet Diesel Issues?

Fredward · February 09, 2015, 12:01:17 PM

I found an Onan CMQD 7500 Quiet Diesel with 1340 hours on it in a rolled over semi at a local salvage yard. It appears to be OK but have not had a chance to load test it. Includes the remote panel for inside the vehicle. It's a CMQD 7500 7.5HDKAT41934K and I'm not sure what the difference is between this and the RV models.

How should I go about testing it? I need a variety of loads to put it through its paces. They want $2,500.00 for it. Seems like a good deal to me but I've seen posts about trouble shooting these Onans and who knows what might have happened to it in the rollover.

Fred

luvrbus · February 09, 2015, 12:24:52 PM

If it will start and run 2 roof tops it will power anything

somewhereinusa · February 09, 2015, 02:31:19 PM

I've had two quiet diesels, both threw a chunk off of the rotor, at that point it's more expensive to fix than it's worth. I now have two perfectly good Kabota diesels with relatively low hours that I'm going to use for something else.

Utahclaimjumper · February 09, 2015, 02:34:13 PM

My 7500 QD has 2300 trouble free hours on it and still going strong.>>>Dan

luvrbus · February 09, 2015, 02:54:06 PM

They do throw the magnets off and will destroy the head I had to replace mine because of that, the magnets are just glued on the rotor, Cummins said it was bad glue sorry but we can't help you

Charles in SC · February 09, 2015, 04:25:12 PM

If the 7500 is like my 8000 and I think it is, there are two 110v outputs on it. I would be sure to test both outputs. They do not make 220v when used together. They are separate circuits if that makes since. I have 1300 hours on mine. I had to replace a sensor once but otherwise it has been great.

OneLapper · February 09, 2015, 04:46:31 PM

Assuming that the generator wasn't running when the tractor rolled over, and assuming that there isn't any physical damage to the unit, I would think that it would work fine. I would pull the glow plugs out and turn the engine over by hand to see if oil got into the cylinders. If no oil comes out, crank it over with the starter (glows still out). If no oil still, re-install the glows and start it up. Remember to check the coolant level, and the air cleaner for oil.

$2500 is a really good price if it runs. The only problem with a Onan QD I've personally seen was one with a few hundred hours on it shutting off on overheat protection. The owner was cursing it up and down, mumbling all sorts of things.

You might want to price a replacement rotor and stator, just in case it goes the way that Clifford's and somewhereinusa's went. Just for reference, a new gen head for my Westerbeke is $3800 and only $1250 for my 20kw Generac industrial generator (4 cylinder Mitsubishi propane/NG engine).

luvrbus · February 10, 2015, 05:04:35 AM

Cummins charged me $3845.99 for the head ended up with labor costing $5248.00 and only took 6 weeks

OneLapper · February 10, 2015, 07:38:24 AM

Quote from: luvrbus on February 10, 2015, 05:04:35 AM
Cummins charged me $3845.99 for the head ended up with labor costing $5248.00 and only took 6 weeks

Ouch! Looks like you got my usual "discount" of List plus 100%, plus tax. It's a special club.... welcome.

TomC · February 10, 2015, 07:41:21 AM

Just remember that the generator is variable speed. That might make for fitful sleeping on a hot night everytime the A/C kicks on, the generator speeds up. Good Luck, TomC

Oonrahnjay · February 10, 2015, 07:46:05 AM

Quote from: TomC on February 10, 2015, 07:41:21 AMJust remember that the generator is variable speed. That might make for fitful sleeping on a hot night everytime the A/C kicks on, the generator speeds up. Good Luck, TomC

I specifically bought my 8K "old technology" non-inverter type Onan diesel generator for that reason. I bought it in late '11, installed it in early '12 and have used it since. Do the loose magnets happen to the older-style, steady-rpm models???

luvrbus · February 10, 2015, 09:57:20 AM

It does tick you off Cummins knew about the problem as far back as the late 90's but offered no help or a recall

Lin · February 10, 2015, 10:45:46 AM

Is it possible that Cummins or another source would be able to say what years of manufacture had that issue so you could know what to avoid or upgrade?

luvrbus · February 10, 2015, 10:57:56 AM

Maybe a dealer like Dave here on the board would but you won't get any info from Cummins,I heard anything past 2003 was good to go you just fight the control boards going bad after that

Fredward · February 10, 2015, 04:36:18 PM

I looked at that generator today. It is a CQMD 7500 HDKAT all right. The case has rust spots on it. I took the outside housing off. It's a 2006 model according to serial number lookup and the hour meter says 1324. Could it have 13,240 hours on it? 1324 in nine years is 174 hours a year on a generator mounted on a semi tractor. It's real dirty inside under the cover, the generator head is all rusty. I also turned the motor over by hand by turning the cooling fan to see if the cylinders had oil in them. The motor turned real easy; I didn't detect one compression stroke. Does a Kubota D722 have a compression release for starting that would make it that easy to turn?

Also the wires are broken off the electric throttle coil stator (on the injection pump) so that would need replacing. I'm starting to think this thing might be about worn out and might be why the owners left it behind when they crashed the truck.

Things that make me go "hmmmmmmmm"