Onan problem

[Dave Cunningham]

Hey , is there any onan generator experts out there, I am having problems with my 12.5 diesel, in my 03 .
The generator starts right away, smoking like crazy, and usually dies, if you shut off the breaker on the unit itself, on the third startup it will keep running and the smoking clears up after 30 or 40 seconds, then you can turn the breaker back on and it works ok.  I had the generator tuned up when I was in bend a couple of months ago, it was still acting up so I stopped at cummins northwest in Seattle , they diagnosed that it needed a computer control board. Got back to Victoria and ordered anew board from Vancouver ( $1000.00) put it in yesterday ,and guess what, nothing changed, and of course they won't take the board back.
Oh, and when the unit dies the first couple of times it is flashing a code 13, wich is supposed to indicate low output voltage. Also when it is running, you can load it up with everything running in the motorhome and the idle never changes.

Dave
Ps the unit only had 30 hours on it when I got it, it has about 100 now

[John Hennessey]

does it smoke every time you start it up?  What color is the smoke?

[Dave Cunningham]

Hi John, yes it does smoke every time, the smoke is pretty blue.

[John Hennessey]

Blue smoke signifies incomplete combustion. Could be air/fuel moisture, could be carbon deposits, could be improper valve adjustments, worn injectors. Should never see blue smoke so definitely a problem that needs fixing

[Edward Buker]

I'm not sure if your model has a preheat cycle system. I assume that it is relatively cold where you are going through start ups and wondering if your problem is that the cold start system is just not working. I would ask the Cummings shop that worked on it if you have a preheat system and if that issue was related to the diagnosis of changing of the board. There was a reason they thought the board was bad, if it was not the board, they should know what the other possibilities are that could cause the symptom they were working on, perhaps a bad sensor. The low output error could just be that when cold you are not running on all cylinders until combustion starts evenly. That can cause smoking and rough running also.

When you "load it up" and you say the idle is not changing, I think you mean RPM is not changing. I believe you have a constant speed generator and at 1800RPM it produces 120V 60 cycles. It increases and decreases throttle based on load to maintain that rpm which is normal. It must be running right to do so and when yours is cold it is not. Not sure this is your issue but it is worth understanding the cold start system on your generator and see if it is operating properly....

Later Ed

[John Hennessey]

We have the same generator and ours even on a cold start (we're in Minnesota) it doesn't run blue.  We will get some white smoke if we haven't run it for over a month.

[Dave Cunningham]

thanks guys, Ed, you are correct in assuming i meant the rpm, and that is a good point about the constant rpm, someone suggested that to me , but every other generator i have had always an rpm increase as the load was increased. it is not actually that cold here right now , yesterday when i tried to start the unit it was about 60 degrees out, i think you may be on to something with the cold start system. its tough here on vancouver island, we don't have a cummins onan shop, the closest one is in vancouver, the local rv guys are useless, and the 45' sapphire costs about $ 250.00 each way on the ferry, oh well might have to bite the bullet, or wait till i go south next.

Dave

[Edward Buker]

The generators that increase and decrease RPM like the 7.5K-8K  Onan and the Honda generators that end in (I) like the 3000I use inverters to maintain voltage and sine wave AC output. That type can vary the RPM as the load demands more or less energy. Most of he others are either 1800RPM or 3600 constant RPM generators. The speed of the constant RPM is dictated by the number of poles in the generator.  Sometimes what you hear in terms of noise level increasing or decreasing may be interpreted as RPM but it may just be throttle levels at the given constant RPM. More generators are migrating to electronic inverters.

The 12.5KW Onan mentioned an automatic timed glow plug cold start system. You may be able to look for the glow plugs at the cylinder head, trace the wires and see if you can see 12V being applied for 15 to 30 seconds or so when cold. They look like a small spark plug. Another way to check would be a clamp on DC amp probe on the + feed wire to the generator. When you press the start there should be a delay when the fuel pump comes on and a current draw should be going to the glow plugs at the same time. I would guess it is in the 25 to 50 amp range. If you are not seeing a heavy load before the starter is activated then that system is not working. Another check would be to measure the ohms of each glow plug if the harness can be disconnected. They are likely less than an ohm and should have similar readings. This would only tell you that the glow plug is good, but does not tell you if the control circuit is working properly.

Later Ed

[Dave Cunningham]

Thanks Ed, I will try those tests tomorrow .you would think Cummins in Seattle might have tried some of these things before they sent me on my way, telling me I need a $1000.00 computer.

[Steve Hodgson]

I have similar problem with my Onan 10KW on a 2007 Patriot Thunder. The generator always starts and runs for 8 seconds and shuts down with a code 13. I do not have the smoking problem but the generator always shuts down. I had the same problem last year and Lazy Days replaced the Stator, control card and I think the voltage Regulator. I have an appointment at Lazy Days in April unless someone comes up with an answer to these two similar problems.

[Bill Sprague]

Cummins has a "Coach Care" system.  http://www.funroads.com/coachcare/  Check the list and map towards the bottom.

It might make sense that they have a higher experience and training level for the Onan units we have in our motorhomes.  The Seattle Cummins shop is not on that list.

[Dave Cunningham]

thanks Bill, I will check that out

Dave

[David T. Richelderfer]

I did not see in the posts anything about primimg.  You are priming it for at least a minute... especially if it has not been run for several days or weeks?

Over the Winter I tried to run my generator for at least an hour every three or four weeks.  It would start, then die after a minute or so.  This would happen four or five times.  Then I read the manual and saw where I should be priming it for at least a minute before starting it.  After that lesson, it would almost always start and remain running without dieing... and this was when it was near the freezing point... from 25 F to 35 F.

My generator has just over 600 hours.  I am told it should have a valve adjustment at about 1,000 hours, then it's good for (hopefully) 100,000 hours... assuming regular service maintenance.

[Dave Cunningham]

David,

what do you mean by priming , when i start the generator, i hold the switch as it preheats and it just starts when it is ready, how do you prime it,
now the problem has gotten worse, it used to run forever, once it was warmed up , but now dies after about 20 minutes of running.

Dave

[Bob Jae]

Here is what the manual says.

PRIMING THE FUEL SYSTEM
The fuel system should be primed after replacing the fuel filter or running the genset out of fuel. To prime the fuel system hold the control switch down in its Stop position for at least 1 minute.