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Racor pre-filter location

Discussion in 'Musings With Maine Sail' started by Renegade135, Jul 11, 2018. Add this thread to a FAQ

  1. Renegade135

    Renegade135

    Joined Oct 30, 2013
    10 posts, 0 likes
    Wauquiez Gladiateur
    US Anacortes
    This may not be the right forum, but I have a fuel filter location question. The motor is an old but well running volvo md7b. I am going to upgrade and relocate the fuel pre-filter. Current setup is a completely (at least to me) inaccessible volvo prefilter and a standard screw on filter on the motor. I want to mount a new Racor prefilter in an accessible location. The prefilter appears to be gravity fed from the fuel tanks. Does it matter if I mount the prefilter further from the tanks, and higher than the tanks within the engine compartment so I can make them accessible? I assume the fuel pump will provide enough suction for the system.
     


    Last edited: Jul 11, 2018
  2. Don S/V ILLusion

    Don S/V ILLusion

    Joined Sep 25, 2008
    5,051 posts, 273 likes
    Alden 50
    US Sarasota, Florida
    Elevating the primary filter might be convenient but brings the likelihood of unintended consequences such as sucking air into the fuel system.
     


  3. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,686 posts, 518 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME

    If you want to mount the filter above the level of the tank you'll want to ensure it has an anti-drainback / check-valve. Racor has them and mandates this in their installation instructions in order to "maintain prime"..
     


  4. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    1,673 posts, 565 likes
    Catalina 36 MK1
    US Everett, WA
    You will probably wan to add a lift pump if gravity is no longer your friend. The lift pump should go between the filter and the engine. 4-6psi and 15+ gal/hr.
     


  5. Dan_Y

    Dan_Y

    Joined Oct 13, 2008
    445 posts, 43 likes
    Hunter 36
    US Hampton
    Yard mounted a Raycor 500FG about 18 inches above tank in previous boat and because of the internal check ball and good lines/installation, it didn’t loose prime for the 5 years we had it. Just shut off the tank fuel valve when changing the element, though it probably doesn’t matter with that filter.
     


  6. JimInPB

    JimInPB

    Joined Aug 22, 2017
    957 posts, 268 likes
    Hunter 212 & 170
    us West Palm Beach
    Why between the filter & the engine? I normally mount them between the tank & the filter. That way, when I change the filter, I can prime it with the pump.
     


  7. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    1,673 posts, 565 likes
    Catalina 36 MK1
    US Everett, WA
    Rancor specifies that as the prefered orientation. It still primed the filter just fine. If you use vacuum gauge to determine filter “fullness” they only work if the pump is after the Racor. I suspect you’ll have less leakage also.

    Les
     


    jssailem likes this.
  8. JimInPB

    JimInPB

    Joined Aug 22, 2017
    957 posts, 268 likes
    Hunter 212 & 170
    us West Palm Beach
    Thanks. Those are valid considerations. Apparently, your pump has better suction than mine. Mine would not draw fuel into an air bound filter.
     


  9. Mickstr

    Mickstr

    Joined Jun 1, 2007
    149 posts, 15 likes
    O'Day 322
    US Mt.Sinai
    I added a 12VDC fuel pump as an aide to bleeding my 2GM20F, and also added a few valves so I can by-pass my engine and polish my fuel. The pump specified mounting a filter upstream of it to protect the pump, so I did. No issues pulling fuel into the 500FG filter.
     


  10. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,907 posts, 575 likes
    Catalina 34
    224 CA Maple Bay, BC, Canada
    Because the primary filter, what you call the pre-filter, is supposed to do just that: filter. There is a small filter in the bottom of most fuel pumps, but it is NOT what you want and need as the first line of defense of filtration.
     


    NYSail likes this.
  11. Richard19068

    Richard19068

    Joined Jun 11, 2004
    695 posts, 46 likes
    Oday 31
    US Redondo Beach
    Why between the filter & the engine? I normally mount them between the tank & the filter.

    I thought it was because the pump might "emulsify" (for lack of a better term) any water in the fuel before it got to the filter and thus make the filter less effective at removing the water.
     


    JimInPB likes this.
  12. JimInPB

    JimInPB

    Joined Aug 22, 2017
    957 posts, 268 likes
    Hunter 212 & 170
    us West Palm Beach
    Emulsify is the correct term. I had not considered that possibility. I also don't know the minimum droplet size that the water blocking filters can stop.

    In practice, I have not had any issues with any of the systems I have set up with the pump before the filter, but depending on what type of pump was used, I suppose that in some cases emulsification could be an issue.
     


  13. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,182 posts, 568 likes
    Beneteau 323
    US Annapolis MD
    Going way back, I have always read that electric pumps PUSH better than SUCK fuel.
     


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  14. JimInPB

    JimInPB

    Joined Aug 22, 2017
    957 posts, 268 likes
    Hunter 212 & 170
    us West Palm Beach
    I guess that you are protecting from a situation in which the crud in the tank is big enough to jam up the pump. I haven't had that situation yet, but I can see where it could happen.

    After reading all of this, it appears to me that the following is a summation -

    Putting the pump before the filter has the advantage of allowing you to power prime the filter after a filter change, but runs the risk of emulsifying water into the fuel & helping the water to maybe get past the filter, depending on the type of filter & pump.

    Putting the pump after the filter, but before the motor, protects the pump from debris in the intake line, but runs the risk of an airbound filter preventing the pump from getting a prime & working.

    In the past, with the pump after the filter, I have needed to pour fuel into the filter housing when I change the filter, otherwise the pump would not work. That is why I chose to put my pump first. I now see that there are risks involved that I had not considered.
     


  15. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    1,673 posts, 565 likes
    Catalina 36 MK1
    US Everett, WA
    Or all of you who use priming as s reason to put the pump between the tank and filter, have you tried it the other way?? These lift pumps have really good suction, I’ve bench tested both cheap turbine and expensive facet lift pumps at over 4’ of suction and the pumps could fill the Racor.

    If your having problems you probably have a air leak which would be a fuel leak with the pump the other way

    The reason I put the pump in between the Racor and the engine is because that’s what the installation instructions say to do. They have smart engineers that I trust. Plus I can use vacuum gauge to tell me when I need a filter change.

    Les
     


  16. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,686 posts, 518 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    Racor wants to see the pump on the suction side for the best filter performance. I have never seen a good quality pump that could not prime a Racor filter from the suction side..
     


  17. JimInPB

    JimInPB

    Joined Aug 22, 2017
    957 posts, 268 likes
    Hunter 212 & 170
    us West Palm Beach
    I am using the clear view filters. Those are required to be above deck by regulation. If my filter was lower in the boat, I would probably not have the issue with priming.
     


  18. jssailem

    jssailem

    Joined Oct 22, 2014
    5,897 posts, 2,061 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    @JimInPB Les's point about air infiltration is a good point. Perhaps the issue is the pump. Check out the spec's on this one.
    http://walbrofuelpumps.com/frb-11.html
    • Self-Priming (Dry Lift) of more than 48" (120 cm)
    • Continuous Duty Life Over 18,000 Hours (Diesel Fuel)
    • Dry Run to Four Hours
    • Low Current Draw
     


  19. IStream

    IStream

    Joined Nov 14, 2013
    155 posts, 6 likes
    Catalina 50
    US Seattle
    Regarding water in the fuel, Racor filters are hydrophobic and will not absorb or pass water droplets larger than their nominal pore size. As long as the water is not dissolved in the fuel and, if emulsified, the water droplets are bigger than 2/10/30 microns (pick your filter), it won't get through. A diaphragm pump simple can't emulsify water to that degree. You'd need a high speed gear or impeller pump and even then, it's tough to get a droplet size in the 10um range so it can pass through the filter.
    Note that some fuel filters are designed with a hydrophillic medium to absorb dissolved and/or highly emulsified water but the Racor filters for the common turbine units aren't that design.
     


  20. Richard19068

    Richard19068

    Joined Jun 11, 2004
    695 posts, 46 likes
    Oday 31
    US Redondo Beach
    Whatever, but Racor says this.
    "Pressure Side: ... Not ideal - pumps emulsify water hindering filter performance."
     



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