Fuel/Water Separator turning black

Discussion in 'Trucks [ Eighteen Wheelers ]' started by TruckkinItUp, Dec 15, 2021.

  1. TruckkinItUp

    TruckkinItUp Bobtail Member

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    Jan 8, 2020
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    Somebody please help,

    2016 Redtop Cummins ISX 400hp bumped to 430hp and deleted

    I've been going through on average 2-3 Fleetguard FS19764 filters weekly for months

    -truck is serviced every 12k miles and main primary fuel filter always looks clean when changed

    -davco housing was replaced

    -plastic fuel lines going to Davco housing get warm but not hot no matter outside temp from changes in weather they're always warm

    -had flaky black sediment at one point in bottom of davco housing but really haven't seen anymore in awhile when draining

    -fuel tanks have always checked clear of algae but still ran algae killer in them

    -ATF has been mixed with fuel directly in davco and also added to tanks on occasion
    -nothing is fixing it

    -filter starts to discolor at various fuel levels in site glass of davco

    -truck just had an In-frame @ 660,000
    *Guys at shop were thinking potential combustion getting past injector tips .
    All injectors were sent off and tested..

    2 were bad and replaced, the rest checked out good so all injectors were deemed fine by shop and installed 2 weeks ago yet the problem persists with filter issue

    -now they're thinking to add a "top cool" on one of the fuel lines but that seems only like a band-aid without finding the actual cause. ?
    *Truck was fine until all of a sudden the problem started and has threw everyone for a loop.

    -I change the filter when I notice my fuel mileage drop..6.3avg. then drops to 5.8m.p.g normally and pop the hood to find fuel/water separator black/gray again.

    -fuel in davco always looks normal but filter discolors badly killing fuel mileage and engine runs rough

    -I change the filter and my m.p.g goes right back to normal

    -i solely run fleetguard filters and only fuel at Loves due to company discount.


    This has been a real nightmare and I would greatly appreciate someone solving this issue.
    It's become very costly:(

    Thanks in advance,

    TruckkinItUp
     
    Last edited: Dec 15, 2021
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  3. TruckkinItUp

    TruckkinItUp Bobtail Member

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    Jan 8, 2020
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    20211203_152046.jpg
     

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  4. TruckkinItUp

    TruckkinItUp Bobtail Member

    17
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    Jan 8, 2020
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    I had just changed that filter and as you can see the discoloration on the very bottom of the filter ..that was enough to drop fuel mileage,making truck run sluggish, and I had to replace it within probably 600 miles, if that.



    20211208_093147.jpg
     
    Last edited: Dec 15, 2021
    Pamela1990 Thanks this.
  5. bryan21384

    bryan21384 Road Train Member

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    Do you fill up every time you fuel?
     
  6. TruckkinItUp

    TruckkinItUp Bobtail Member

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    Jan 8, 2020
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    It varies..
     
  7. bryan21384

    bryan21384 Road Train Member

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    If you don't fill up every time, that black stuff will appear in your fuel water separator. Filling up each time, and not letting it go below ¼ tank will keep that from happening. That way you'll only have to change it when you get a service.
     
    TruckkinItUp Thanks this.
  8. little cat 500

    little cat 500 Road Train Member

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    fuel tanks are full of crap look in the fuel cap
     
    TruckkinItUp Thanks this.
  9. Pamela1990

    Pamela1990 Road Train Member

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    Are these filters all from the same batch, stored in the same place?

    Or have you been buying them at different places, different times?
     
    TruckkinItUp Thanks this.
  10. Goodysnap

    Goodysnap Road Train Member

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    I think you may be chasing nothing.

    Clean the fuel system and buy clean fuel from reputable suppliers.

    Are you changing the filter just on how it looks? Wait for the fuel level to rise in the globe. When it reaches the top, then change it.

    Make sure to clean the sep bowl every service.
     
    GYPSY65 and TruckkinItUp Thank this.
  11. TruckkinItUp

    TruckkinItUp Bobtail Member

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    Jan 8, 2020
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    -I've done this and it doesn't work.
    It seems a little better but problem still comes back.


    -Driver side tank had "trash guard" removed on tank to be able to look inside,clean,and drain nothing was out the norm.
    Shop said if trash wasn't in one tank it wouldn't be in the other..


    -I had a box of 12 I had bought at one point but went through those and bought randoms and all the same...same problem driving me nuts$$


    -It had flake/sediment at one point ..draining the bowl into bottles I'd see it time to time but it's been clear of that for awhile yet still going through filters left and right.







    I really appreciate all the replies trying to help .

    This is one that is giving me alot of costly trouble and no one has been able to find the problem:((
     
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