Forum Discussion

n4hwl's avatar
n4hwl
Explorer
Aug 05, 2013

What is this gunk in my fuel filter?

My onan diesel generator recently stopped running. I found that the fuel filter was clogged with some sort of reddish/brown gunk that looked like mud or dirt. I changed the filter and now the generator runs fine. When I got home I found this same reddish/brown gunk in the bottom of my fuel filter to the cat c7. It was down in the clear plastic cap on the bottom of the filter. The engine was still running fine. I replaced the cat fuel filter with a new one. Here is a picture of the gunk that came out of the cat fuel filter. I filtered the fuel through a paper towel to catch it and try to figure out what it was. What does it look like to you. It has the texture of mud but it is still wet with fuel.

Thanks

Ken

I just realized that I don't know how to attach the picture I have of this gunk. When I figure out how I will attach it.

Ken
Class A

23 Replies

Sort By
  • wolfe10's avatar
    wolfe10
    Explorer
    Aug 20, 2013
    Sounds like a good homemade fuel polishing system.

    I was trying to picture it off your existing coach filters and didn't see a way for it to work properly, as the primary filter is on the suction side of the lift pump. And the fuel from the secondary filter is really needed for head cooling and lubrication in addition to that fuel that is burned.

    Good job.

    Brett

    Jay58 wrote:
    Bert
    The filters and pump hang on a fence next to where I park.
    The fuel tank drain plug has been replaced with a nipple 90 , nipple, ball valve, brass barb hose adapter.
    I have plugged a 4" hose section to place over barb as a second safety seal.
    The valve handle is on top of the pipe next to the tank and the leveler crossmember is 6"forward of the drain.
    When parked the inlet hose to the filter assembly is attached and the discharge from the filter assembly is a hose to the filler on the moho.
    I bought an extra filler cap and drilled a hole which I sealed to allow hookup w/o rain getting in.

    I don't filter unless I'm home then it runs at least two days a week at 40gph. I chose this setup rather than on board since in the future I will trade up.
  • J-Rooster's avatar
    J-Rooster
    Explorer
    Aug 20, 2013
    daytripper63 wrote:
    Have you ever filled up with Bio-diesel? Veggie oil is a great lubricant and fuel system cleaner but the only problem is it will sludge up your filters
    Thanks for the info I was unaware of this!
  • Jay58's avatar
    Jay58
    Explorer
    Aug 20, 2013
    Bert
    The filters and pump hang on a fence next to where I park.
    The fuel tank drain plug has been replaced with a nipple 90 , nipple, ball valve, brass barb hose adapter.
    I have plugged a 4" hose section to place over barb as a second safety seal.
    The valve handle is on top of the pipe next to the tank and the leveler crossmember is 6"forward of the drain.
    When parked the inlet hose to the filter assembly is attached and the discharge from the filter assembly is a hose to the filler on the moho.
    I bought an extra filler cap and drilled a hole which I sealed to allow hookup w/o rain getting in.

    I don't filter unless I'm home then it runs at least two days a week at 40gph. I chose this setup rather than on board since in the future I will trade up.
  • Jay58's avatar
    Jay58
    Explorer
    Aug 20, 2013
    I've actually installed a valve and barbed fitting to 1, allow me to drain off the bottom AND recirculate the fuel to the tank after going through a racor 215 fuel water separator then a 10 micron and 2 micron filter then fuel pump back to the tank.
    No more trash or water. I also use biokleen
  • n4hwl's avatar
    n4hwl
    Explorer
    Aug 20, 2013
    I drained my tank and found a lot of rust in the bottom. I have always kept it full when stored but I have not owned it its whole life.

    I now have new clean filters and will keep an eye on them.

    It sure was a pain having to pressurize the tank with air to get the air out of the line back to the filter and start the engine but it worked fine.

    Ken
  • wolfe10's avatar
    wolfe10
    Explorer
    Aug 20, 2013
    Jay,

    Would be curious as to how you plumbed it. Please describe your fuel system-- i.e. if two fuel filters, normal is primary fuel filter/water separator, lift pump, secondary fuel filter, injection pump/engine.

    Thanks.
  • Jay58's avatar
    Jay58
    Explorer
    Aug 20, 2013
    I've actually installed a valve and barbed fitting to 1, allow me to drain off the bottom AND recirculate the fuel to the tank after going through a racor 215 fuel water separator then a 10 micron and 2 micron filter then fuel pump back to the tank.
    No more trash or water. I also use biokleen
  • n4hwl's avatar
    n4hwl
    Explorer
    Aug 09, 2013
    I am about to decide that this gunk in my tank is at least partially rust. If this is coming from the inside of my tank what can be done? I do try to keep my tank full at all times while being stored. I am planning on draining my tank when I can use the fuel down to a very low level. I have talked to the fuel specialist that can clean the tanks at the rally I am going to in Atlanta in October. I will update when I get the tank drained and report what kind of junk I get out.

    Ken
  • wny_pat1's avatar
    wny_pat1
    Explorer
    Aug 08, 2013
    wagonmaster2 wrote:
    I'll always by-pass a station if I see a tanker filling the tanks (at least ask the driver if he's dumping diesel or gasoline as I'm using diesel) but is there anyway to know whether or not a tanker may have just left the station? How long after a delivery would you guess it takes for the gunk to settle back to the bottom of the tank?
    I use to deliver a lot of ARCO stations on weekends because their drivers were off. ARCO use to have a policy of not pumping product for 1 hour after the fuel transport left the station. Don't think they do anymore. Other companies kept right on pumping while we dumped.

    wagonmaster2 wrote:
    Do you have any idea how far off the bottom of the fuel tanks the pick-up might be for the pumps we are using to fill our RVs with? Are we always using off the bottom of the fuel storage tanks?
    The tanks are set up with the fill pipe about 6 inches off the bottom of the tank. We were required to dip the tank with water paste to determine how much water was in the tank. Had to write it on the delivery receipt. It was seldom over 3 inches, usually much less. The station managers were "suppose to" pump the water out daily each morning. This is why you are smart to avoid a station or truckstop that is getting a delivery.
  • DougE's avatar
    DougE
    Explorer
    Aug 05, 2013
    Rust or sludge you got from a fill up. I had to change filters a dozen times before I got all the cr*p out from one really batch. Most pumps have filters these days so it's not as common.

About Motorhome Group

38,718 PostsLatest Activity: May 03, 2025