Onan generator shuts down

[Mjresq4]

I have a 9kw Onan diesel generator that starts fine but will only run for a short time then shut down. Some times it will only run for 30 seconds to a minute other times it will run for a few minutes.

 

[Jaybeaux]

When it shuts down, there will be a code of blinking lights that should help you. A couple of things that come to mind:

1. Good cooling water flow?
2. On my 420, I have a tank selector valve next to the cockpit sink in a cabinet. Switching it over to the other side one time, without my glasses, I inadvertantly switched it to "OFF". Genny ran for about 30 seconds.
3. Is oil pressure good? Good oil level?

Good luck. Keep us posted.

Jaybeaux

 

[Buyajet]

I have a 9kw Onan diesel generator that starts fine but will only run for a short time then shut down. Some times it will only run for 30 seconds to a minute other times it will run for a few minutes.

If it’s not getting water, it will shut down, if it’s not getting fuel, it will shut down. There are several sensors between fuel and delivery on the unit. Each can sense an issue, each can fail. Like Jaybeaux said, the lights will usually tell the story. DO NOT UNDER Any circumstance keep trying over and over. After about the third try you can backwash water into the system. Ask me how I know. I’d call a tech or if you are handy check coolant, clear heat exchanger or service it and see if that is a causal issue. There is a hi/lo fuel sensor, that can cause it and so on. Be careful again to not continue to try to make it run until you find out why. Onans are very “smart”. Much smarter than me.

 

[Mjresq4]

Hopefully, I will make it there Friday to check the items listed. Thanks for the ideas. My Gen is stuffed in the port aft corner and not very easy to access because of the 8" diameter exhaust tube that run on the port side of the port engine. Here is my next question, how hard is it to remove the exhaust tube? It looks like I can slide the rubber sleeves at each end and then remove the tube. Also, is that tube filled with water and will water come into the boat through it? My guess is the water should only come in up to the water line.

 

[Mjresq4]

They say a picture is worth a thousand words. So here it is. For any future readers of this thread, the generator showed fault code 7 "loss of raw water flow". Note this is for an Onan MDKBL generator, the codes are different for different models.
Thanks for the info Jaybeaux and buyajet

 

[alnav]

View attachment 89494 They say a picture is worth a thousand words. So here it is. For any future readers of this thread, the generator showed fault code 7 "loss of raw water flow". Note this is for an Onan MDKBL generator, the codes are different for different models.
Thanks for the info Jaybeaux and buyajet

You're going to want to get all the piece that fell off that impeller out of the system, almost to the point of reassembling it to make sure. Easiest way I believe is to take the end caps off the heat exchanger, most if not all bits will be there. The diameter of the exchanger is just about perfect for using a small vacuum cleaner hose.

 

[Ranger Mike]

You have found the source of your shut-down problem. For future reference though, let me add an experience I had with GenSet shutdown. I always do my own oil/filter changes. Once, about three years ago on a previous boat,I was pressed for time and decided to have the local marina mechanic do my oil/filter changes for me. Dumb me, I didn't check his work. The next time I started the GenSet, it ran for 5-10 seconds and shut down. After doing that a couple of times I started looking for the problem, and it turned out there was no oil in the generator. The marina mechanic had drained it, changed the filter, but forgot to add new oil. Fortunately, as soon as I added the oil it ran fine with no residual problems. I was fortunate. Lesson learned!

 

[Mjresq4]

You have found the source of your shut-down problem. For future reference though, let me add an experience I had with GenSet shutdown. I always do my own oil/filter changes. Once, about three years ago on a previous boat,I was pressed for time and decided to have the local marina mechanic do my oil/filter changes for me. Dumb me, I didn't check his work. The next time I started the GenSet, it ran for 5-10 seconds and shut down. After doing that a couple of times I started looking for the problem, and it turned out there was no oil in the generator. The marina mechanic had drained it, changed the filter, but forgot to add new oil. Fortunately, as soon as I added the oil it ran fine with no residual problems. I was fortunate. Lesson learned!

Ranger, thankfully as Buyajet pointed out the gens are smarter than us and know to shut down.

 

[Jaybeaux]

View attachment 89494 They say a picture is worth a thousand words. So here it is. For any future readers of this thread, the generator showed fault code 7 "loss of raw water flow". Note this is for an Onan MDKBL generator, the codes are different for different models.
Thanks for the info Jaybeaux and buyajet

Glad you sorted it out. Like others have said, you have to retrieve those broken off pieces of the old impeller. They are jammed at the heat exchanger and probably restricting your water flow a bit inspite of that shiny new impeller you just installed. Removing the endcap can be a bit tricky with the oil filter in place. I you want to be thorough and make the job much easier, do a mid-season oil filter change.

Jaybeaux

 

[ocgrant]

Just a quick question, when was the last time the impeller was replaced?

 

[Mjresq4]

Just a quick question, when was the last time the impeller was replaced?

ocgrant, Based on what the PO stated, about 3 years ago. This is only my second season with this boat. PO said the impellers for the generator and mains as well as the heat exchanger service were done just before I bought the boat. So I guess I have to take that for what it's worth. And yes, to all of you wondering that after this, if I have ordered a set of impellers for the mains also.