Replacing The Fuel Filter in Our RV’s Onan Generator

TheRVgeeks Annual Maintenance, Generator, Maintenance 37 Comments

Our RV just turned 10! We took delivery on May 17, 2005, so its birthday present was a new generator fuel filter.

Three years ago, our first two Onan generator maintenance videos showed how to change the oil & oil filter, clean the spark arrestor, replace the air filter, flush the cooling system and replace the anti-freeze. Since then we’ve received multiple requests to show the fuel filter replacement.

Having solar panels and being frugal with power, we tend to keep the hours on our generator to a minimum. The fuel filter only gets replaced every 500 hours, so we haven’t had to do it since prior to making our very first YouTube video, nearly four years ago. Finally, here it is!

We’ve seen quite a bit of discussion about this being a tricky job, but it’s actually a breeze. If we weren’t videoing it, we could easily complete the job in about 15 minutes (shooting video seems to make any project take about 5 times longer). wink

We have an Onan 7.5 kilowatt QuietDiesel generator. If you have a different model, be sure to check your owner’s manual for possible differences in the procedure.


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Comments 37

  1. I have the exact same generator in my 2000 Discovery, Serviced the complete system, oil / filter and diesel filter. The generator would not start prior and it still won’t with it flashing 3 times on the switch which I read it means it ‘needs service’. Question, is that an additional filter in line to the right in your video (and on my generator) the copper colored one that looks an inline filter round and a couple inches long?

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      Hi Richard. We don’t believe there is any additional fuel filter. The one we showed being replaced in this video is the only one. About the code you’re seeing… there should be two codes, not just one – a first stage code, followed by a second stage code. If you look in the manual, you’ll see directions for how to get the second digit (second set of flashes) that you need. Three flashes is only the first stage, so you need the second stage number to hone in on the problem in more detail.

      1. Thank you for the response. As a followup I got the secondary code, ’21’ which translates to, “service required”, which told me absolutely nothing, lol. I ended up disconnecting the fuel line and ran a line into a 5 gallon can of diesel, the generator started after priming and ran fine. I ended up running a complete new fuel line to the RV’s fuel tank and solved the problem, there were cracks in the original line where it went into the main tank, it was sucking in air. One thing about diesels is if it turns over but won’t start it is usually a fuel issue which is probably where I should have started in the first place. Thanks again.

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  2. I have a 1998 Georgetown motorhome and a cant get gas to the gen. will not come out of the gas line. where is the fuel filter locateed

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      Hi Jimmy! Unfortunately we don’t have a gas rig, so we only have experience with a diesel generator. That said, there is one thing that’s probably the same on both types of rigs, and the first thing we would check: the fuel level. Since they don’t want someone to accidentally use up so much fuel by running the generator that the tank runs dry, the fuel pick-up for the generator is usually located higher on the tank. So you can only run the generator down to about 1/4 tank or so, before the gas level falls below the generator pick-up line. So the very first thing to do is make sure you have enough fuel in the tank to be above the generator pick-up line (if you have half a tank of gas or more, then that certainly can’t be the problem. If that’s not it, we’d suggest checking out the website of our good friend Brian of RV With Tito (http://www.rvwithtito.com). He has a Class C gas motorhome with an Onan gas generator. We just checked, and he has a video about troubleshooting the generator fuel pump that might have some useful information for you. That video is here. If that video doesn’t help, he may have other related videos that do. Barring that, Brian is a very handy DIY RVer, who would be happy to try to help if you contact him through his website. Tell him the RVgeeks sent you, and said Hi!

  3. I have a used 2003 Forest River Sierra Sport toy-hauler with the Onan Micro-Quiet 4000 gas generator. It is bolted to the frame of the trailer on the driver’s side. According to the owner’s manual the fuel filter is on the left lower side when looking at the generator. It looks to me the entire generator has to be removed from the compartment to access the fuel filter. Is there an easier way to get to this filter? Thoughts, ideas, suggestions would be appreciated.

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  4. Another great video. How many quarts of oil do you use? I have the same generator. I guess I should open the manual.

    I am surprised the fuel filer can go 500 hours before changing good to know.

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      Thanks Jay! The oil capacity is listed as 3 quarts, but I recall that it seems to take a little more or a little less than that (I can never remember which until I do it each year). ;-)

  5. Great video but a question…

    When you are doing the flush phase and use “fresh water” are you using “normal” water or de-ionized”?

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      Radiator flushing is done with regular tap water right out of the hose, which the instructions on the flushing solution bottle say is perfectly fine (and it uses enough water that you probably wouldn’t want to bother with bottled water anyway). We then use de-ionized/distilled water for filling, which is actually also optional, but recommended. The Onan manual says “The water used for engine coolant should be clean, low in minerals, and free of corrosive chemicals. Use distilled water if available.”

      Hope this is clear and helps!

  6. I have an Onan 8HDKAK generator but it does not have this type of fuel filter. Mine is round and has hose clamped on each end. It is also bolted to the frame by some type of star nut. How do I break the factory hose clamps. The replacement filter that I received has two clamps that you screw down with a screwdriver. I don’t want to accidentally cut the hose when trying to pry off the factor crimped on hose clamps.

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  7. As usual – a completely detailed explanation of the what, when and how of system maintenance.
    I’ve just purchased my 1st rv and the videos you’re providing are going to not only save me a substantial amount of money in mechanic’s fees, but also help me avoid mistakes that could leave me stranded. Experience is a great teacher; however, I prefer the experience of deriving benefit from proactive maintenance – to – that of wrestling with a breakdown on the side of the road in the middle of nowhere!
    Thank you!

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  8. Fixed my problem I’ve been chasing for the past 1.5 years….Generator would run for 1.5-2 hrs then shut down with a 36 error code. Changed the fuel filter using your video and generator it running like new! Thanks for the informative video.

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  9. New owner of an ’03 Teton, first 5th wheel. Your website is just what this semi-skilled DIY guy needs. Keep up the good work. Jim

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  10. Keep putting out the great videos!

    Owning a 2005 Mountain Aire 43 ft myself I find these videos very relevant and informative.

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  11. Your videos are confidence builders. We’re planning to purchase a Newmar Ventana soon we hope. Watching your videos makes me feel more comfortable with the prospect of properly maintaining it. It’s clear that, after 10 years in your Newmar, you are maintenance experts. Thanks so much for taking the time to create your videos.

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  12. Another great video! You make the undesirable jobs look easy. I liked the tip on keeping the fuel from running down to your elbow. Keep up the good work!

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  13. Tiffin motorhomes are known to TWO fuel filters for the diesel generator. If you ever have a fuel delivery error code, it could be the other fuel filter which is hard to find. Owners should call Tiffin Motorhomes with their VIN number to get location of the second filter.

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  14. Excellent video, all your videos are awesome detailed oriented I have learned a lot thanks so much guys.

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