Onan generator stops after 2 sec.

[bigp]

Hi everyone. I have a problem with the Onan generator on my 45 DS. I ran it once this summer and after about 30 mins it stopped. The red switch (fuse?) was automatically turned off. When I try to start it now, it starts and run for 2-4 seconds before the red switch turnes off. Checked the oil dip and it seemed fine.  Any clue?

[Zanshin]

Which model Onan do you have? The engine seems to have just fired when that red switch trips, that is too early for an overload on the output side or internal engine condition (e.g. no water flow for cooling).

I'd like to see the manual on what that switch actually is. Is the voltage on the generator starter battery high enough? If the voltage is low that would raise the amperage flowing through a fuse when the starter motor is engaged, but that is unlikely. All of the Cummins-Onan generators I've had (hmmm, 2 of them, so not a great amount) had a flashing light error code display somewhere on the panel to indicate that the fault was.

If the generator stopped after 30 minutes of running the typical causes are the impeller not letting sufficient cooling water to flow and/or a high-load causing the engine to overheat and shut itself down.

[bigp]

Hi Zanshin and thanks for your reply. When I first tried it out today (first time since it stopped in july) it fired up at once and ran for 5 sek. Second time i tried after a minute or so, it ran for approx 3 sec. Next time, as the video clip showes, it only ran for one second.

Here´s 3 pictures of the generator, and it´s the red button that flips down at the same moment that the golden sylinder shaped part (marked with a red stroke in one of the pictures) pulls the little arm towards it. 


photos.app.goo.gl/cirRTqMikfvYQixWA


And here is the info sheet: 

files.eneq.webnode.gr/200000102-b0d35b1cd1/5.5MDKUB.pdf

[Zanshin]

The cylinder you refer to is the fuel quantity adjuster. That regulates the RPM of the engine. Is the double-breaker below the red switch in the right position (it is spring loaded, so will move easily into the "open" position but have resistance going to the "closed" position, and it should be "closed"). What is that red button to the left? Does it say "fluid breaker"? I have to run now, but will see if I can locate a shop manual with more details.

[bigp]

Oct 31, 2019 6:52:37 GMT Zanshin said:

The cylinder you refer to is the fuel quantity adjuster. That regulates the RPM of the engine. Is the double-breaker below the red switch in the right position (it is spring loaded, so will move easily into the "open" position but have resistance going to the "closed" position, and it should be "closed"). What is that red button to the left? Does it say "fluid breaker"? I have to run now, but will see if I can locate a shop manual with more details.

Thanks, I will go out to the boat later today to try to read fault code from the blinks on the switch inside (if it has that option?). I will also look at the things you mention. The most important I have to do now is to winter-secure the generator, because it is getting below zero here in Norway. It is difficult to get the anti-freeze into the generator if I can´t get it started .

[Zanshin]

I checked the online manual and unfortunately there are no blinking lights on this generator. One manual shows that there is a relay behind the panel which you could replace (24V SPDT - get at any car shop) and it looks like there are only a couple of possibilities for your breaker tripping. The manual says it is a 15A breaker which really should be enough. That cylinder that moves the throttle, can you move it by hand? That draws a bit of power and it might just be a coincidence that the breaker trips when that starts moving.

I am looking for a wiring diagram or shop manual for this generator, that would go a long way in allowing you to diagnose your problem.

www.gemo-online.de/pdf/onan/MDKUB_parts.pdf

[Zanshin]

Found it - I have service manuals for all of my components since they are a lot more useful than the operating manuals.

You should download onan.xmsi.net/981-0512%20Onan%20MDKUB%20MDKWB%20Service%20Manual%20(6-1994).pdf

The electrical schematics are on Page 2-6.

There are several possible sources for tripping the breaker - any of the sensors for temperature/pressure/cooling might be broken and give a false signal. The fuel pump or the fuel adjuster might be stuck and causing high amperage.

Page 2-8 onwards has a good flowchart for problem diagnosis, the impoortant part is:

Has control circuit breaker CB8 opened? YES = Check B+ wiring for shorts to ground causing excessive current draw. If none, check control circuit breaker CB8 for improper wiring. Check fuel solenoid adjustment.



Do you have a multimeter and the willingness to diagnose the problem? It will take some time to do, but with the manual you've got the tool you need. Otherwise it might be worth getting a technician and supplying him/her with the manual.

[bigp]

Oct 31, 2019 17:08:07 GMT Zanshin said:

Found it - I have service manuals for all of my components since they are a lot more useful than the operating manuals.

You should download onan.xmsi.net/981-0512%20Onan%20MDKUB%20MDKWB%20Service%20Manual%20(6-1994).pdf

The electrical schematics are on Page 2-6.

There are several possible sources for tripping the breaker - any of the sensors for temperature/pressure/cooling might be broken and give a false signal. The fuel pump or the fuel adjuster might be stuck and causing high amperage.

Page 2-8 onwards has a good flowchart for problem diagnosis, the impoortant part is:

Has control circuit breaker CB8 opened? YES = Check B+ wiring for shorts to ground causing excessive current draw. If none, check control circuit breaker CB8 for improper wiring. Check fuel solenoid adjustment.



Do you have a multimeter and the willingness to diagnose the problem? It will take some time to do, but with the manual you've got the tool you need. Otherwise it might be worth getting a technician and supplying him/her with the manual.

Wow, you are very helpful. Many thanks !!! I will download the manuals and go out to the boat this weekend and try what you suggest.

What I also have to do if i cant get it started, is to winter conserve it, so that she salt water inside it does´nt freeze. We have minus degrees here in Norway now. I must therefore try to drain it from salt water. Do you know how to drain the salt water without starting it? Thanks to the manual you sent me, I can se where the inlet and outlet of raw water is. Maybe if i open both and blow air into one of the holes, I will get the salt water out?

If i get to start the generator it´s much easier. Then I just replace the salt water intake with anti-freeze and run the generator for a couple of minutes.

[Zanshin]

The heat-exchanger is the lowest point of the engine. If you can't get the system started then you could remove the impeller assembly and open up the drain plug on the heat exchanger to drain the salt water into the pan. There are a couple of liters of water in there, so it is best if you have a little pump. Then you can open up and clean the heat exchanger (this is where the little broken bits of the impeller end up), close it and fill in antifreeze from the impeller pump assembly.

The work isn't difficult ---- EXCEPT ---- if access is a problem as it is on my boat.

I just realized that there's a lot more seawater in the system after the generator (the mixed water/gas exhaust and manifold and then the line to the outside of the boat) and that needs to get antifreeze as well, so it looks like the best solution is to get the generator running.

[bigp]

Nov 1, 2019 14:13:12 GMT Zanshin said:

The heat-exchanger is the lowest point of the engine. If you can't get the system started then you could remove the impeller assembly and open up the drain plug on the heat exchanger to drain the salt water into the pan. There are a couple of liters of water in there, so it is best if you have a little pump. Then you can open up and clean the heat exchanger (this is where the little broken bits of the impeller end up), close it and fill in antifreeze from the impeller pump assembly.

The work isn't difficult ---- EXCEPT ---- if access is a problem as it is on my boat.

I just realized that there's a lot more seawater in the system after the generator (the mixed water/gas exhaust and manifold and then the line to the outside of the boat) and that needs to get antifreeze as well, so it looks like the best solution is to get the generator running.

Yes, I think I just have to get that thing started. I will also look for the seawater-filter/strainer to see if it is blocked by any items from the sea. I will post the news after I have checked it more this weekend. Thanks for being so helpful.

[bigp]

Nov 1, 2019 14:13:12 GMT Zanshin said:

The heat-exchanger is the lowest point of the engine. If you can't get the system started then you could remove the impeller assembly and open up the drain plug on the heat exchanger to drain the salt water into the pan. There are a couple of liters of water in there, so it is best if you have a little pump. Then you can open up and clean the heat exchanger (this is where the little broken bits of the impeller end up), close it and fill in antifreeze from the impeller pump assembly.

The work isn't difficult ---- EXCEPT ---- if access is a problem as it is on my boat.

I just realized that there's a lot more seawater in the system after the generator (the mixed water/gas exhaust and manifold and then the line to the outside of the boat) and that needs to get antifreeze as well, so it looks like the best solution is to get the generator running.

[bigp]

I finally got the generator started by holding the fuel quantity adjuster with my hand so that i did´nt cut the engine. But when I tried to run anti-freeze through the inlet, it would´nt take any of it. So I checked the impeller and found that it was completely worn out. Probably the problem that caused the stop and maybe why it has been shutting off at once after the stop. I will order a new and I will let you know what happens when i replace it.

[Zanshin]

I'm glad you got the engine fired up, and my Cummins chews through impellers like candy (well, maybe not quite that bad, but the impellers do go frequently) and those bits of nitrile get stuck in the heat exchanger, so if you have access to the front plate while working on the generator then it is worth cleaning out those pieces to prevent the problem from recurring.
I wonder what the issue with the fuel adjuster is, though. Perhaps it is the electronics shutting down the engine when they detect no water flow through the cooling system.

[bigp]

Nov 4, 2019 6:43:06 GMT Zanshin said:

I'm glad you got the engine fired up, and my Cummins chews through impellers like candy (well, maybe not quite that bad, but the impellers do go frequently) and those bits of nitrile get stuck in the heat exchanger, so if you have access to the front plate while working on the generator then it is worth cleaning out those pieces to prevent the problem from recurring.
I wonder what the issue with the fuel adjuster is, though. Perhaps it is the electronics shutting down the engine when they detect no water flow through the cooling system.

Yes, I will try to open the heat exchanger, but it is located on the rear side, so maybe a bit difficult? Like you say, I also hope the electronics is shutting down the engine because of no water flow. I will order the new impeller today and will post an update when it is mounted.

[Zanshin]

Don't forget to order 2 and have one as a spare