Results 1 to 13 of 13

Thread: K75 Hissing noise from fuel tank

  1. #1
    Registered User
    Join Date
    Sep 2012
    Location
    Howell, Michigan
    Posts
    5

    K75 Hissing noise from fuel tank

    I have a K75 1992 with 48K miles. I parked it for 2 weeks in the garage, it was running fine. Sunday, I started the bike and a hissing sound is coming from the gas tank, it sounds like a air leak. I pulling the fuse for the fuel pump and the sound quit the motor ran 2 seconds and then died. Put the fuse back in and the sound came back. Today I removed the gas tank filler cap everything looks clean and in good order. With the cap off I started the engine and the sound is still there. If you put your ear on the tank the sound is louder on the left side which is the side were the pump is located. I felt the rubber fuel line feeding the fuel rail and you can feel the fuel pump pulsing but at a totally different frequency then what sounds like air hissing. The sound does not change with RPM.
    I'm thinking that it is the fuel pump but before I buy one for $230 does anyone have another idea of what it could be? Thanks, Dan

  2. #2
    Registered User kgadley01's Avatar
    Join Date
    Dec 2006
    Location
    South Carolina
    Posts
    3,533
    Quote Originally Posted by DanK75 View Post
    I have a K75 1992 with 48K miles. I parked it for 2 weeks in the garage, it was running fine. Sunday, I started the bike and a hissing sound is coming from the gas tank, it sounds like a air leak. I pulling the fuse for the fuel pump and the sound quit the motor ran 2 seconds and then died. Put the fuse back in and the sound came back. Today I removed the gas tank filler cap everything looks clean and in good order. With the cap off I started the engine and the sound is still there. If you put your ear on the tank the sound is louder on the left side which is the side were the pump is located. I felt the rubber fuel line feeding the fuel rail and you can feel the fuel pump pulsing but at a totally different frequency then what sounds like air hissing. The sound does not change with RPM.
    I'm thinking that it is the fuel pump but before I buy one for $230 does anyone have another idea of what it could be? Thanks, Dan
    How much fuel is in the tank??? when the fuel gets low on most older K-Bikes, you can hear the whine of the fuel pump. Fill it up and listen again.
    AKA SNAPGADGET
    Lifes too short to ride an ugly Motorcycle

  3. #3
    Registered User
    Join Date
    Sep 2012
    Location
    Howell, Michigan
    Posts
    5
    The tank had about 3 gal left in it with the sound then I fulled it to just below the flap still the sound.

  4. #4
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    3,393
    Remove the filler cap assembly and look into the tank while it is running and making the noise. May be a split hose or a split filter.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  5. #5
    Registered User
    Join Date
    Sep 2012
    Location
    Howell, Michigan
    Posts
    5
    Good thinking. Yesterday, when I had the filler off the tank was full, I'll remove the gas to below the filter and look for a leak.

  6. #6
    Registered User Beemer01's Avatar
    Join Date
    Mar 2007
    Location
    Chicago, Ill
    Posts
    1,019

    +1

    check the fuel filter and internal lines - I've actually seen fuel filters split from either pressure or freezing with water in the tank.

    Way cheaper than a fuel pump.

  7. #7
    Registered User
    Join Date
    Sep 2012
    Location
    Howell, Michigan
    Posts
    5
    Drained the the tank except for about .5 gal. Started the bike everything looks fine. Felt the pump with the engine running, nothing wrong.

  8. #8
    Registered User Beemer01's Avatar
    Join Date
    Mar 2007
    Location
    Chicago, Ill
    Posts
    1,019

    Just flailing here

    There is a vent in the gas cap to allow air to enter as the fuel is consumed - do you hear the hissing when the flap is open and the engine running?

  9. #9
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    A steady hissing would indicate otherwise; when my fuel vent was blocked I would always hear a brief "whoosh" every time I opened the tank but it never was a steady hiss.

    Bet it's something like others have suggested and I'm also curious as to the final diagnosis/outcome.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  10. #10
    Curmudgeon At Large Bobmws's Avatar
    Join Date
    Mar 2003
    Location
    Astatula, FL
    Posts
    1,127

    A couple WAG's

    Could it be vibration?
    Is the pump mount securely clipped into the tank?
    Is the rubber damper deteriorated?
    Bob Weis
    '04 K12RS - Hannigan Hack
    www.earplugco.com

  11. #11
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085

    What it's probably not

    One additional WAG since it just occured to me; it's probably NOT the fuel pump itself as I believe if and when one goes bad it just up and dies (usually when you're out in the middle of nowhere).

    Really does sound like some kind of fuel filter or ruptured fuel line (inside the tank) problem to me (but I am far from being any kind of expert on these things*).

    *Everything useful in life I learned either in kindergarten, out on the long road or here in the MOA Flying Brick forums.

    Btw, one of the first things I would do in your situation is go to Napa and get a $5 fuel filter (IIRC it's Napa 6061 but will edit this if I find out otherwise right after I post this) and replace the one you have. It's dead simple, all you need to do is remove the filler cap, take a long flat blade screwdriver and undo a couple of hose clamps. That leads me to another thought; maybe one of your clamps inside the tank is not tight enough?

    Anxious to hear what ensues; I just got through redoing my own fuel lines which needed renewing although they were not the cause of the problem I was having. It's a good feeling to know you have the proper gear in place, regardless.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  12. #12
    Registered User
    Join Date
    Sep 2012
    Location
    Howell, Michigan
    Posts
    5
    Well the hissing sound is still there. Sunday was a nice day so I went for a 70 mile ride, the bike ran great. I'll try and find another K75 and listen to the tank. Other then that the bike is going to be put up for the winter.
    Thanks everyone for your input, Dan

  13. #13
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    Your call, Dan, but if it was me I would want to get to the bottom of it before putting it away for the winter---just wondering might drive me crazy!

    Are you sure it's a hiss and not a whine? All K75s whine like a sewing machine, you know. The whine is more pronounced at low fuel levels, too.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •