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  • Onan 5500 run issues

    Could use some help troubleshooting my generator issue. Unit is late 2019, and never used the generator much since we always had 50A hookups. I'd run it periodically for 10 minutes and that was it. Fast forward to this weekend. We were out camping any my wife became ill. Long story short I have the camper in the parking lot of the hospital and she will be here another couple days.

    Generator had some issues running. It ran fine for an hour or so, then shut down at 1/4 tank. Read that it needed over 1/4 tank. Luckily gas station couple hundred feet away. Filled the tank up with fresh fuel and it struggled to start. Got some carb cleaner and put it in the fuel line a couple times. It would run fine for for about an hour and shut down. Put some fuel cleaner in the tank, carb cleaner in the fuel line and tried again. It then ran fine. 4+ hours. I was in the hospital so not sure when it shut down. Came back out and it was off. Engine was hot so it couldn't had been long. Started it back up a couple times and went into town, was running fine when I came back. Went in the hospital, came back out after 4 hours and it was off again.

    So it will run for 4-8 hours fine. Then it will just quit. Started it up this morning and it ran for 20 minutes and quit. Wouldn't start up. Let it sit and it started back up and has been running for about 30 minutes fine now.

    Any thoughts what the problem is? Is it just some old fuel getting sucked up killing the engine? I have read that sometimes the oil is overfilled and it shuts down after 20 minutes. Yesterday it ran for long periods of time though. If it was carb issue I would think it wouldn't run fine for 6 hours and then just shut down. The code is 36 which is generic for shutdown without input. It was 98 out yesterday and I was able to maintain 72 in the camper until I came out at night and it was off. It's supposed to be just as hot today too.
    2020 GD 320G
    2021 Ram 3500 H.O. SRW.

  • #2
    According to the troubleshooting for that code it indicates a fuel issue. Either a clogged filter or dirty carb type issue. I would lean towards the filter considering your infrequent use and the likelyhood of stagnant fuel in it. Modern fuel doesnt store well. I think if it was a dirty carb then it wouldnt run well all the time. If you can get a new fuel filter for it thats where I would start. You should also check the oil level due to the heat. It doesnt indicate a low oil for that code but it helps to rule it out.
    2021 Reflection 337RLS, 2021 Silverado 3500HD 6.6 gas. Nellie the wonder boxer

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    • #3
      Any idea where the fuel filter is? I see the fuel line, it appears to go into a hard line from the base of the generator. FWIW I am not sure how a clogged filter works, but when it stopped and I pulled the fuel line off, it did pump gas out when I hit the start button. Would a clogged fuel filter allow fuel to come out?

      Oil level is full. I watched a video that if the oil was too full it would shut the generator down. It ran for 6-8 hours in 98 degree heat though so I find it hard to believe that would be the issue. The camper was about -.7 degrees low in the front. I filled the truck bags up which brought me to -.3 degrees. Will see if that helps any. I did not unhook from the truck.

      This morning it seemed to be running fine for 1.5 hours. Went to get coffees, walked past the camper and it was off again. It's been starting right up after it shuts off which is a good sign.
      2020 GD 320G
      2021 Ram 3500 H.O. SRW.

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      • #4
        Laying under generator right front.
        Click image for larger version

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        Jim and Cindy
        2021 F350 DRW 7.3L
        2021 320G

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        • #5
          The fuel filter is where to start consider the history of the unit. It could easily be something else but you have to start with the basics. I only mentioned oil just to rule it out, I always start with the cheap and easy stuff first.
          You are correct that the generator fuel pickup is typically at the 1/4 tank (approximate) level
          Unless I was using the generator regularly I would keep "rec fuel" ethanol free fuel in the tank.
          2021 Reflection 337RLS, 2021 Silverado 3500HD 6.6 gas. Nellie the wonder boxer

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          • #6
            Thanks for the quick replies! I didn't even look under the generator. The hard line saw must be the fuel filter. There are 3 auto stores within a block of me, but none have the filter or cross referenced filter on their website. I will have to run there and see what they have.
            2020 GD 320G
            2021 Ram 3500 H.O. SRW.

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            • #7
              Unless its a direct replacement part you may have trouble. I cant tell if the blue clamp is reusable or not, you may have to cut the rubber hose and replace the clamp. You may luck out of someone can cross reference the Onan number, Amazon showed a few generic options
              I see a Wix filter 33049 listed as a direct cross, O'Reilly carries Wix or you could try NAPA which sells Wix filters under NAPA part # 3049
              Make sure you get a new clamp also
              2021 Reflection 337RLS, 2021 Silverado 3500HD 6.6 gas. Nellie the wonder boxer

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              • #8
                Originally posted by familytruckster4 View Post
                Unless its a direct replacement part you may have trouble. I cant tell if the blue clamp is reusable or not, you may have to cut the rubber hose and replace the clamp. You may luck out of someone can cross reference the Onan number, Amazon showed a few generic options
                I see a Wix filter 33049 listed as a direct cross, O'Reilly carries Wix or you could try NAPA which sells Wix filters under NAPA part # 3049
                Make sure you get a new clamp also
                Well I might be in the clear. After filling the airbags up and raising the front a little, the generator seems to be running good again. 7 hours so far without a shut down. I'm leaning towards either the high oil switch, or it's enough out of level that the carb isn't happy? Or all the old fuel is now out of it and the fuel cleaner is doing it's thing.

                I will change the filter with oem when we get home if it stays running overnight. I was able to remove the upper hose with metal clamp and put the hose back on without taking the clamp off. I have some small one if it doesn't work.

                Fingers crossed it stays running.
                2020 GD 320G
                2021 Ram 3500 H.O. SRW.

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                • #9
                  RoyB Glad it's running good, fingers crossed for you. My money would be on bad fuel as well, hopefully you finally got through it. If you're headed back to full hookup land after your hospital stay (hope everything works out okay there), I'd recommend burning off what's in the tank and filling it with ethanol free. Ideally you'd find a way to get the bottom 1/4 out of there as well. For stabilizing it, I've got a buddy that's a marine mechanic and her swears by the Mercury product. I chased bad fuel in my snowmobiles for years, tried Stabil, Seafoam, you name it. The Mercury stuff always performed for me. They've got three levels, a cleaner, a storage, and an combination of the two.

                  http://www.mercurymarine.com/en/us/p...cts/fuel-care/
                  Neil Citro
                  2018 Reflection 28bh
                  2019 F350 6.7L Long Bed Crew Cab

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                  • #10
                    Good news. I agree on the fuel issue.
                    My personal opinion would be to use the Wix filter since its less than half the price of the Onan. We had at least a dozen gas gens at work that we serviced and we used the Wix or Baldwin on them and never had any issues. Same with the oil filters. If you can find a match in a Fram or a Wix I buy those for half of what the OEM's cost. My Kohler engine on my lawn tractor has a Bosch on it that was the same filter my Jeep wrangler used. The Bosch cost me $3 at Menards, the Kohler filter is around $11
                    Best wishes
                    Scott
                    2021 Reflection 337RLS, 2021 Silverado 3500HD 6.6 gas. Nellie the wonder boxer

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                    • #11
                      One other trick you can try to help you get by is to try a higher octane fuel. Higher octane fuels contain more chemicals that act as cleaning agents for old fuels.

                      Fuel filter issues are hard to diagnose because a clogged filter will let the engine get enough fuel to fill the carb bowl (or fuel pump for injectors) and possibly run at low power requirements. As demand for fuel increases, the flow rate is restricted thus not allowing enough fuel to maintain proper air / fuel mixture to run.

                      You can listen to the generator running and if it sounds like it misses a beat (not backfiring but just flat out miss) then recovers, you may have a fuel delivery issue. I have a generator that does that. Only thing I can figure is I changed from the factory screen to a true fuel filter and I could literally watch the filter drain of fuel and fill with vapor.
                      Joseph
                      Tow
                      Vehicle: 2018 GMC K2500 Denali Diesel
                      Coach: 303RLS Delivered March 5, 2021
                      South of Houston Texas

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                      • #12
                        Joseph,

                        Premium fuel as a better cleaning agent is a myth. The only primary benefit of high octane fuel is that it contains a higher knock number (i.e. higher octane rating). Engines calibrated for regular will actually lose torque in using premium (slower burn rate) and will only cost the customer more money. Engines calibrated to premium fuel will make more torque since the ignition timing is more advanced and closer to a term referred to as MBT.

                        Jim
                        2017 Imagine 2600RB
                        2015 GMC Sierra 4x4

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                        • #13
                          RoyB Oil level procedure is fairly specific on an Onan. If oil level is not correct and with the rig off level, the oil sensor could be shutting you down. Fuel issue seems to have been ruled out after being able to run up to 7 hours.

                          https://www.youtube.com/watch?v=iZvkG7HJA9k

                          https://thecampingadvisor.com/onan-generator-starts-then-shuts-down/#tab-con-4


                          Jim
                          Last edited by MidwestCamper; 06-22-2022, 07:22 AM.
                          2017 Imagine 2600RB
                          2015 GMC Sierra 4x4

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                          • #14
                            I am not sure what octane the Onan is designed to run at. I have been putting 91 in this weekend (highest avail). It's 100 degrees out and I am working it hard running the AC all day. I like to run higher octane in extreme heat to reduce any chance of detonation. It's not that out of level. about 1/4 degree both ways.

                            The generator ran for a good 12 hours yesterday. It shut down right before I Got back last night since it was still cool inside. It was about 1/4 tank. I went and threw another 5 gallons in and it ran all night without a problem. Put another 5 in this morning. It seems to be using about a .8-1 gal an hour with the AC running all day. I set the temp a little warmer today. Probably don't need to keep it at 72 when I am not in it. The good news is the system will maintain 72 off the generator in 100 degree full sunlight. I think it cycles between the 3 of them so the generator isn't overloaded.

                            I will change the plug and filter when I get back. Also keep a spare filter on board as well. I appreciate he help everyone!
                            2020 GD 320G
                            2021 Ram 3500 H.O. SRW.

                            Comment


                            • #15
                              Originally posted by MidwestCamper View Post
                              RoyB Oil level procedure is fairly specific on an Onan. If oil level is not correct and with the rig off level, the oil sensor could be shutting you down. Fuel issue seems to have been ruled out after being able to run up to 7 hours.

                              https://www.youtube.com/watch?v=iZvkG7HJA9k

                              https://thecampingadvisor.com/onan-generator-starts-then-shuts-down/#tab-con-4


                              Jim
                              There are several discrepancies from the Youtube video and whats actually in the Cummins/Onan manual.on page 3-3 https://www.cummins.com/sites/defaul.../0981-0159.pdf
                              Nowhere does it describe the scenario of running it 30 mins and waiting 6-7 hrs. It also says to fill the oil to the full mark, not what the Youtuber says. And oh BTW, oil does not "expand"
                              He also states that 15w40 is only for diesels when the graph on 1-5 shows that 15w40 actually offers the widest temperature range of service. Most modern 15w40 oils such as Mobil Delvac 1300 or Shell Rotella also carry the ratings for use in spark ignited engine (gasoline or LP)
                              Like so many other cases of Youtubers its big on advice from a guy thats just another RV owner, I prefer the manuals.

                              Also note that page 1-4 shows the fuel must be minimum 87 octane, indicating that it will run on 87. I would however be diligent about not using some of the "super88" octane thats out there right now since this contains 15% ethanol and the vast majority of small engines are not designed for anything more than 10%
                              Last edited by familytruckster4; 06-22-2022, 05:57 PM.
                              2021 Reflection 337RLS, 2021 Silverado 3500HD 6.6 gas. Nellie the wonder boxer

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