Generator Questions

[Sean Marconette]

Rob,
Have you had any luck with the generator? A few weeks ago I measured what mine burned in one day. This was with A/C running, fans, computers, tv, battery charger and 110 vac pump and chiller running for 8 hrs straight. 7 gallons. It surprised me that it did not use more fuel than that.

Sean

We just purchased our first RV; also have never owned a generator. The motorhome is a 2007 Jayco Greyhawk 31SS with an Onan 4000. The generator has 800 hours on it but the RV only had 9,000 miles. Upon delivery (when we got home) even though we tested everything the generator would start fine, run for 5 minutes, and then die. The dealership put a new carburetor AND fuel pump on it at no charge to us. Seems to run perfectly now.

We plan, of course, to change oil regularly and use it a little more (I've read it's bad to let them sit) but my question is how many hours can I expect out of this generator before it needs replaced or major service?

Thanks.

Wendy & Scott

[Matt Schurman]

Congrats on your RV purchase, I hope it treats you well!

The Onan microquiet 4.0KY genset is very durable. With proper care and maintenance it should last around 5,000 hours! I use the same model in my trailer and its been very reliable. It requires some routine maintenance, but nothing crazy. Your owners manual has excellent schedules for maintenance, I recommend you take a look at them.

On my machine, I change the oil every 100-150 hours, there is no oil filter. Change the air filter as needed, probably once per season. Change the spark plug once per season as well as the fuel filter, which is located on the fuel pump inlet fitting. I also check the valve lash and adjust it once per year. I average about 500 hours per race season on the machine.

Good luck to you

Thank you Matt!

[NHRA1285]

Hi, I have a good one. 2002 Journey DL with a Onan 7500 Quiet Diesel. A few months ago it quit while running normally. I tried to restart but would just try to run against he starter. I changed out the fuel filter not knowing when it was last done and it started ran fine.
Fast forward to last week. I was giving it some routine exercise at the shop. Ran it for about an hour. Once again it quit while running nomally. Tried to restart, same syptoms. Just for giggles I changed the fuel filter. It tried to run against the starter but that was it. I packed it in for the day.
As you know when you first push to start the fuel pump runs momentarily then the starter engages. Now the pump clicks once and a second fainter click is heard under the dash and that is it. No roll over. I checked the codes. First is a 3. Second level is a 17 to which is not in my manual.
A few questions. Any idea as to what is going on? It looks to me like the gen has to come out through the bottom of the coach for any type of in depth service. Am I right?
And lastly how much of a PITA is that job? Thank you for your time. I do appreciate it. Holgar

[Don Higgins]

I have been battling a 10 K Onan generator that will run all day at times then slowly shut down every 30 minutes at night. The code it generates is 36.

I put a new fuel filter, air filter, checked all tubing for plastic bags and changed the oil and filter. The engine is the Isuzu. The only thing I can say that may help is the fuel pump return line stops pulsing when the engine was about to die. When I pushed the return line over to the side to restrict it the engine sprang back to life.

I think the fuel pump isn't pumping or the board isn't telling the pump to continue pumping. I will replace the pump this week but do you have any other ideas? Slate Cummings was having the exact same problem this week but he replaced the pump and it still slowly dies every 30 minutes.

[Mark Lewis]

I have a Onan Marquis 5500, model # 5.5BGMFA26105H.
Do not know the hours on it and it runs good .Unit is at least 13yrs old.
I recently had to replace the fuel pump.
The only issue I have is it seems to get lugged down when I turn the AC on, has a 13500 roof air unit on trailer.
Is there anything that needs to be done to the generator part as far as routine maintenance goes? All I have is a 5 gal hot water heater and microwave besides the ac.

Thanks for the help
Mark Lewis

[Rich Biebel]

Mark......Those older Onans run well and should easily run your AC and other items at the same time. The rated output on a 5500 is about 45 amps at 120 volts. An ac unit probably draws no more than 15 amps and a microwave maybe 10, Hot water heater I would guess another 10 tops so you are well within the generators capability.

The older Onans were flathead engines. 1800rpm. They tend to carbon up heavily inside the cylinder heads and intake ports. The rear intake port often is much worse with that carbon buildup. The engine supplies the power to spin the rotor of the generator. The magnetic field created as load increases is the load the engine sees. So if the engine is weak it cannot "carry the load" of the magnetic field in the generator. There is basically nothing in the generator end to service other than the brushes. They are either good or bad and if they are bad you will not have any AC output and the unit will likely not stay running due to loss of AC output.

The first thing to do is make sure the std tune-up items are good and if the machine has a lot of hours on it......a heads off carbon cleaning might be what it needs. Valve lash is also a big factor that causes them to run weak. Exhaust valves get tight, not enough lash and once the engine is hot they run poorly from improper valve seating. lash is .005 Intake and .013 exhaust cold.

I remove the heads......remove the manifolds.....clean the carbon in the heads and ports and the backs of the valves. Adjust the valve lash and reassemble it.......Carb has to be good.....Governor arm and all adjustments set carefully under load for best operation. I use a resistive load bank on all the units I service and repair. Everyone gets tested and adjusted with no load and right up to full rated load. Carbs are very sensitive on mixture and governor arm adjustments.....

[Hit-Man]

Originally Posted by Don Higgins

I have been battling a 10 K Onan generator that will run all day at times then slowly shut down every 30 minutes at night. The code it generates is 36.

I put a new fuel filter, air filter, checked all tubing for plastic bags and changed the oil and filter. The engine is the Isuzu. The only thing I can say that may help is the fuel pump return line stops pulsing when the engine was about to die. When I pushed the return line over to the side to restrict it the engine sprang back to life.

I think the fuel pump isn't pumping or the board isn't telling the pump to continue pumping. I will replace the pump this week but do you have any other ideas? Slate Cummings was having the exact same problem this week but he replaced the pump and it still slowly dies every 30 minutes.

Don I was doing a search and seen this old thread. Did you replace the fuel pump on your 10k onan and do you remember how it came out was it difficult ?

If you could e-mail me at 1952rrc@gmail.com regarding I would appreciate it

[Matt Schurman]

Good Morning.

The last two posts require different responses, which will both lead in similar directions. So bear with me, this stuff is work....lol

First, NHRA1285, your code 17 is a fuel pump fault code, which is trigger by the controller unable to sense the electric pump. This is a bypassable fault, which means it can be reset and ignored, but that information is pretty much useless if the machine won't run. When the control doesn't "see" the fuel pump in the circuit, it won't allow the engine to crank, it just drops right into a fault 17, so the fuel pump and wiring needs to be tested.

Your unit is installed without regard for making this type of repair within the confines of a Class A motorcoach. Without seeing the installation I can't say for sure but I'm fairly certain it will have to come out to chase this problem down. It's a big pain and yes, it will probably come out the bottom of the coach. We use a forklift and a great deal of cursing. Give me a call to discuss, I think I can help you more over the phone with some of the details. 800-821-5973