Onan 4KW Generator


Junior Member
I recently bought a '96 Dutchmen Class C from a friend of mine. He gave me a good deal on the RV because it needed some TLC put into it. He is not a DIY'er and knows very little mechanically. He took care of the RV and had it serviced regularly. If anything was done to it, he kept the paperwork on it. I had to remove everything from the overhead because a leaking roof vent had rotted all but the metal frame. I learned quickly how the RV was constructed.

The RV came with the 4KW Onan generator. Not long after I purchased it I had to replace the starter on the generator so I learned how drop and raise the generator back into place. I recently developed a problem in that the genny would start, run for about 15 seconds, and shut off. I checked the two switches that are used to start & stop the generator. Both worked. I dropped the geneerator & checked the fuel pump; it was working. I limited the problem down & thought that the Control board was faulty. I spoke with a shop in NW Alabama. A new board would cost me $375. The shop would not UPS/FedEx or mail the part. I would need to drive to Alabama to get it. The price of the item made me dig a little deeper into the problem.

I removed the Control board from the floor of the generator. Nothing looked burned or out of order. I happen to notice that under the board on the generator floor was a lug with several wired connected it to it. It was being used as the ground for the generator. I found a wire that had vibrated off the lug so I placed it back, put the board back in its place, & started the generator. It has been running without incident since then.

To those of us who work / maintain our RV´s maybe this will help. There are some old messages in the Forum that were posted some years ago that have mentioned a problem with the generator, not running properly as did mine. When the generator or RV loses a good ground to the chassis, there are a lot of problems that come up.


Junior Member
How do you drop the generator, I have the same style but I'm not getting 120v out of it. I've changed the circuit breaker out but it didn't help. I would like to drop it and ck the slip rings but have no clue how to do it. Thanks


Junior Member

I do not know what you have but would be limited on my knowledge anyway. Mine has eight bolts, two per side, to drop it from the frame of the RV. The generator is heavy so it will need to be dropped with a jack. I use a 3 1/2 ton floor jack to drop mine to set it on four blocks of wood or bricks. The cover has four bolts that need to be removed so you can get into the inward workings. If you have to remove the generator from the RV, you might have to jack up the RV so the generator will be able to be removed. The "headache" is removing the cables from the generator. Mine is not easy to do.

I hope this helps and is not too late. Incidentally, there is a trouble-shooting guide online, but I have forgotten where it is located. You should be able to find it with a Google search.


Junior Member
The troubleshooting guide is put out by Flight Systems. The guide is really good and the parts are well made, even better than the originals, and carry a good guarantee. I did the "troubleshooting guide for Onan 4kw generator" and the .PDF guide was the first to be listed. If you are having problems with the generator, I suggest printing the guide. It helped me find my problem and saved a bunch of labor costs!


New Member
As a diesel mechanic in semi-retirement, I can tell you that often crud in the tank or in the fuel filter will cause problems. If you don't use your generator often, especially in the winter, it's a good idea to spend 6.00 and get some diesel purge. You can buy ten cans on E-bay for 66.00 and share with someone. This stiff dissolves all the tiny bits of dire that clog injector holes. It also does a better job than any Dry Gas (not to be used in diesels) because it is the type of hydrocarbon that lubricates injection pump and injector surfaces as it dissolves the goop.
Also, check the bottom of your fuel tank. On an Onan, they are not super big. Empty the junk out and drop a can of Diesel purge with any trans fluid or SAE oil and you will be surprised at how quiet the diesel runs. Onans are noisy, especially the air-cooled ones, so this is an added benefit.

The other thing that causes the condition you mentioned is a cracked rubber/synthetic rubber fuel line, Those are less than 5.00 to replace and always a good idea.

Good luck!