Onan Marquis Gold 5500 generator failure

[Grabcon]

My Outlaw has an Onan marquis gold 5500 generator, I have owned this RV since September 2021 and really have not tested the generator for long periods. I do run it once a month and it seems to operate fine.

The other day I was running it under load it ran for about 30 minutes and then it shut down on it’s own. At that time I did not know that there was an error code sequence on the start button so I don’t know the error code if any. After that it would not start and stay running from either the remote or local start switch. If I hold either start switch it will start but as soon as the button is released it will shut down. If I hold the start switch it stays running until released. Then dies.

After waiting 24 hours it did start and ran until I shut it down. It ran about 15 minutes and it was producing 120AC and things in the RV did work. Tried to restart immediately and had the same situation as described above. No error code at local switch.

I cannot do test for AC output as it does not stay running but I do know that it produces based on start after 24 hours.

The carburetor does have fuel and the fuel pump does have pressure even after the unit is hot.
The choke pull off appears to operate correctly.
The carburetor was replaced prior to purchase so I am going to assume that it is clean.

After much research I think that the issue is either a bad intake manifold or the Control Board. The Control Board is expensive but can be easily replaced. The manifold may require that the generator be lowered or removed. How big of deal is it to Remove this generator?

I am preparing for 2 weeks of a volunteer project and this is a boon-docking event in March and need the generator operational. My wife and I Fulltime and are currently volunteering for Fish and Wildlife at Balcones Canyonlands NWR, Marble Fall, Tx So we can’t bring the RV somewhere and leave it for repair.

Again I get no error codes but does anyone have some testing thoughts of things to look at?

Thanks.

[bigchick]

did you buy new or used? the onan generator has a two year warranty from onan.

[Grabcon]

Originally Posted by bigchick

did you buy new or used? the onan generator has a two year warranty from onan.

As I said I bought 9/2021 and it is a 2007

[astrnmrtom]

Check your oil level.

Could be a bad oil level sensor.
Could be a bad voltage regulator.

Mine started doing the same thing, each time I got it running it would run for shorter and shorter times eventually not running unless I held down the start button. Mine was a bad voltage regulator. At first it would run a while, then die and not restart. What was happening was the regulator worked until it got hot, then would fail.

Here's a troubleshooting guide, plus this company sells replacement regulators if needed: https://www.flightsystems.com/pdf/on...ting-guide.pdf

https://www.flightsystems.com/

Hope this helps.

[Grabcon]

astrnmrtom thanks for the input. I have talked with two generator repair companies now and they both said that the start button bypasses the PCB and sensors to start and when the button is released the PCB and sensors are engaged which causes the shutdown. I also have no error codes on my start switch so diagnosis is difficult.

I have the guide and used that originally but it really didn't help much. So when talking with the repair guys the first one was not able to look at it for 8 to 10 weeks. The second came out and as we talked he first pulled the brushes which were much easier than I thought it would be. Then he started the generator as soon as it started he released the start button and said that the drive belt between the engine and generator has come off or broke. I asked how he knew that and he said it is the sound that the generator doesn't make, meaning the generator is not spinning.

So the unit needs to come out I can either take the rig to his place or remove the generator myself. I will take it out to save a couple hundred bucks and bring it to him for repair. While it is out he will service the unit, spark plugs, valve adjustment oil, etc. Set the output and generally give it a good check. I asked about the intake manifold and he said with its age he would recommend replacing it since the unit is out of the rig.

More to come next week.

[HarryStone]

Wait. The last time you tried it and it worked, it produced AC power, that tells me the generator side is working. Have you checked the oil level as mentioned above? These generators have a oil level sensor, that will shut down the generator if low.

[Grabcon]

Harry, Oil level is fine. That was one of the first things I check.

[Moesbro]

Mine used to shut off after about 30 minutes, then it got to be about 15 minutes. After cooling down, it would restart. Replacing the fuel pump did the trick, it’s been fine for the last couple of years since. I used an oem onan part.

[theboss1]

Originally Posted by Grabcon

My Outlaw has an Onan marquis gold 5500 generator, I have owned this RV since September 2021 and really have not tested the generator for long periods. I do run it once a month and it seems to operate fine.

The other day I was running it under load it ran for about 30 minutes and then it shut down on it’s own. At that time I did not know that there was an error code sequence on the start button so I don’t know the error code if any. After that it would not start and stay running from either the remote or local start switch. If I hold either start switch it will start but as soon as the button is released it will shut down. If I hold the start switch it stays running until released. Then dies.

After waiting 24 hours it did start and ran until I shut it down. It ran about 15 minutes and it was producing 120AC and things in the RV did work. Tried to restart immediately and had the same situation as described above. No error code at local switch.

I cannot do test for AC output as it does not stay running but I do know that it produces based on start after 24 hours.

The carburetor does have fuel and the fuel pump does have pressure even after the unit is hot.
The choke pull off appears to operate correctly.
The carburetor was replaced prior to purchase so I am going to assume that it is clean.

After much research I think that the issue is either a bad intake manifold or the Control Board. The Control Board is expensive but can be easily replaced. The manifold may require that the generator be lowered or removed. How big of deal is it to Remove this generator?

I am preparing for 2 weeks of a volunteer project and this is a boon-docking event in March and need the generator operational. My wife and I Fulltime and are currently volunteering for Fish and Wildlife at Balcones Canyonlands NWR, Marble Fall, Tx So we can’t bring the RV somewhere and leave it for repair.

Again I get no error codes but does anyone have some testing thoughts of things to look at?
Thanks.

All Onan’s have low oil pressure shut-down systems…so make sure your oil is up to level…checked while the Coach is level. If the Onan has sat for a while it could have other issues. Do the easy stuff first.

[Grabcon]

The easy stuff has been done. Based on the mechanics diagnostics I pulled the generator and delivered it to him today. I will have it back Saturday. He will delivery it back to me.

I will post what the issue(s) was.

[gatorb8]

fuel pumps are cheap and some fail as you described

[RichnSandy]

Hello,

Had a similar problem with my gen model 5HGJAB. It would run for a short time, once it stopped it would not start until the next day. Checked the fuel pump and it seemed to be putting out enough fuel but chose to replace it since it was a cheap attempt. I don’t recall the code it spit out, something regarding unexpected shutdown (maybe 5-7). Ended up taking to a Caterpillar repair shop, they replaced the carburetor and I have not had any issues since. Cost was $1k and I did not get my old carb back to open it up an see what was wrong. Hope this helps.

[astrnmrtom]

Hope you get the generator back and it's good to go.

[donr103]

Make sure you clean the slip rings.. you tube FLIGHT SYSTEMS GEN REPAIR... good luck and keep us posted