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Thread: 92 K75S Fuel injectors are wide open...

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  1. #1
    Rally Rat
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    92 K75S Fuel injectors are wide open...

    Hello everyone,

    I hope someone has seen this problem before and can help.

    The bike was not running. Fuel coming from the exhaust. I pulled the fuel rail and the injectors are flowing wide open continuously when the start button is pressed and until the fuel pressure stops. I've seen these injectors working before so I do know that these are running continuously not just looking like they are. Massive fuel coming out of all injectors.

    Injectors were sent in and cleaned and tested. Injectors are good. Computer, Air Flow sensor, Temp sensor and fuel pressure regulator replaced. Problem still persists.

    I disconnected one plug from one fuel injector and that one is not squirting. So the injectors are getting a solid power signal... Kill switch shuts them off instantly. Also disconnected the TPS with no effect.

    Could it be a short in the fuel injectors wiring harness .? Or the fuel filter is causing a back pressure?

    Please help if you can,

    Michael
    Last edited by MindTrainer; 08-20-2012 at 10:50 PM.

  2. #2
    Rally Rat
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    The last time I saw this, it was caused by a bad FICU. See if you can borrow one from a running bike. It's also possible that your injector switching wire has somehow become grounded. This could be caused by over-zealous use of zip-ties around a harness.

  3. #3
    A bozo on the bus deilenberger's Avatar
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    The injectors are powered ON whenever the ignition is on. They are triggered by grounding the other side of the connector. That is grounded by the L-Jetronic unit. They are wired in parallel - ie - they all fire at the same time.

    Something is grounding out. Quick check - unplug the L-Jetronic, see if they close. If so - L-Jetronic has problems (almost NEVER happens).

    If they then don't close with the ignition on, start following the brown wiring from the injectors backwards toward the harness until you find the ground problem. It's possible the problem is in a harness - which is a real problem to track down but not unknown due to the wire density on K bike harnesses and the small passages the harness is snaked through.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  4. #4
    Rally Rat
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    Stiil open...

    Hello everyone,

    I have been out of town till yesterday.

    Today I replaced the injector wiring harness and to my utter surprise it didn't fix the problem.

    When the fuel injector computer is disconnected there is no fuel squirting...

    Could I have 2 computers doing the same thing? Has this happened to anyone before ?

    Wow I'm really stumped now.....

    Please give this poor guy some more advise...

    Thank you.
    Last edited by MindTrainer; 09-07-2012 at 04:06 PM.

  5. #5
    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by MindTrainer View Post
    Hello everyone,

    I have been out of town till yesterday.

    Today I replaced the injector wiring harness and to my utter surprise it didn't fix the problem.

    When the fuel injector computer is disconnected there is no fuel squirting...

    Could I have 2 computers doing the same thing? Has this happened to anyone before ?

    Wow I'm really stumped now.....

    Please give this poor guy some more advise...

    Thank you.
    Do you have an ohmmeter? That will be the first step in troubleshooting.

    And do I understand correctly - you've tried another L-Jetronic box (the one above the battery)?

    Is this the harness you replaced? http://www.realoem.com/bmw/showparts...24&hg=61&fg=12

    If both are correct - then something is telling the L-Jetronic to fire the injectors.. so it means tracing the wiring to and from the ignition module (located under the seat about dead center in the frame right behind the steering head) since that provides the trigger signal to the L-Jetronic to fire the injectors.

    I don't have a wiring diagram handy anymore, but I'm sure someone can help you out. One WAG (and it is a WAG..) might be the hall-effect-sensor wiring may have shorted out, telling the ignition module that it's time to fire the plugs (and inject some fuel.) But that's just a guess.. so don't spend any money trying it until someone tells you what connectors on what device you want to check for an errant signal.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  6. #6
    Midnight Rider 41077's Avatar
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    Seen it before

    This happened to me, I had flames coming out of my exhaust. Swapped the L-Jetronic box with one from another bike, problem solved.

  7. #7
    Rally Rat
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    Yes and Yes

    Don,

    Yes I replaced the computer under the seat first thing. Yes the wiring harness in the link is the one that I replaced.

    I have books with schematics and will attempt to find the wire responsible.

    i will let you know what i find...

    Thanks for the help it is very much appreciated.

    Michael

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