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Thread: 1992 K75 fuel pressure control

  1. #16
    broadstone
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    1992 K75S fuel pressure

    98Lee, I quoted the wrong book in referring to relieving fuel pressure. It was on page 6.5 (middle of page) of the 1999 Haynes manual that discusses alternative methods of releasing fuel pressure from the rail. It makes sense to me that this would work but, indeed, I still wasn't able to blow air through the return line even with nearly -40 psi of pressure applied to the vacuum line at the throttle body. Because of the significant task of getting to and removing the FPR, I'm actually hoping that someone will convince me that my conclusion re a frozen closed regulator is wrong. Thanks again.

  2. #17
    Curmudgeon At Large Bobmws's Avatar
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    Quote Originally Posted by broadstone View Post
    98Lee, I quoted the wrong book in referring to relieving fuel pressure. It was on page 6.5 (middle of page) of the 1999 Haynes manual that discusses alternative methods of releasing fuel pressure from the rail. It makes sense to me that this would work but, indeed, I still wasn't able to blow air through the return line even with nearly -40 psi of pressure applied to the vacuum line at the throttle body. Because of the significant task of getting to and removing the FPR, I'm actually hoping that someone will convince me that my conclusion re a frozen closed regulator is wrong. Thanks again.
    There have been numerous recommendations telling you to do an actual check of the fuel pressure. Without that knowledge you can not diagnose any further.
    The parts are available at any box store; a brass tee, some barbed hose fittings to screw into the tee, a cheap pressure gauge from the water well section, some fuel hose and some clamps.
    Less that $20 material, less than 20 minutes to put it together and hook it up.
    If your pressure is in the 38 psi range your FPR is fine. If the pressure is high, then you may be correct in your assumption.

    No other way to confirm that than to do the test.

    Following that I would look at pulling the injectors and to see if they are frozen open. If open you should be able to blow through it. You can apply 12V to an injector and should hear/feel it click as it moves. They can be cleaned locally, look for a diesel injection service.

    I know this because I had stripped my former 89 K100RS down for paint, basically had the fuel rail open when I ruptured a disc in my back. 8 months later I was getting everything back together and couldn't get the bike to run. Pressure test showed the FPR was fine, but I found the injectors to be frozen.
    Bob Weis
    '04 K12RS - Hannigan Hack
    www.earplugco.com

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