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Thread: 1990 K75S died suddenly

  1. #46
    Registered User jwetering's Avatar
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    Quote Originally Posted by JamesInCA View Post
    The HES connects to the ignition box, not the fuel tank connector. No HES wiring passes through the connector.

    The four wires in the fuel tank connector include two fuel-level wires, one of which goes to the cluster, and the other to the "connector for additional instruments," power (from the FI relay, through fuse 6), and ground. If you have a problem with the connector, it is with the power or ground wires. Neither touches the HES or the ignition box. I'm very skeptical of this connector being able to affect spark; if you have a common cause it's earlier in the circuit. If you have a separate spark problem and fuel problem, the fuel component of the problem could well be here.
    Thanks guys for sticking with me through this.

    When the fault occurred the other night - I pushed the starter button and the starter motor whirred it's heart out with no fuel pump whine and not a sputter from the engine.

    Then - standing beside the bike - I unplugged the tank without jostling or even touching the tank itself and pushed the starter again. This time the bike sputtered .

    Clearly I had no spark before I unplugged the tank - and clearly I did have spark after I unplugged the tank.

    James - I absolutely agree it doesn't make sense - but it was clearly observed. Furthermore - I had a similar thng happen last week during troubleshooting - although I didn't recognize what was happening at the time.



    Here's the theory - the hot G/W wire going in to the fuel tank is shorting to ground inside the white molded plastic base of the fuel level sender. That G/W comes from the fuse panel which is fed from a G/R wire from the fuel injection relay. The ignition control unit also connects to the fuel injection relay - through the Y/Br wire and it's possible that the short is travelling to the spark box through that wire.

    I have the FI relay on my desk in front of me - -it looks good physically and the contacts don't look burned. Unfortunately - a new one is 3-4 weeks away through my local supplier and it's not cross reference-able to anything off-the-shelf.

    I spent the morning trying to agree that it's a kill switch problem and that the lights on the dash could somehow stay on even though this switch was failing - but I just couldn't get there. Furthermore - the starter button works just like normal and if there's one thing that won't work without a good kill switch - it's the starter button.
    jasper
    north vancouver

    1990 K75S

  2. #47
    Registered User jwetering's Avatar
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    I just ordered a new fuel gauge.

    When I read this thread which Lee posted back on page 1:

    http://www.k11og.org/forum/viewtopic...r=asc&start=30

    and combine it with my theory above - it sounds like the most likely solution.

    Wish me luck lads.
    jasper
    north vancouver

    1990 K75S

  3. #48
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    Quote Originally Posted by jwetering View Post
    Thanks guys for sticking with me through this.

    When the fault occurred the other night - I pushed the starter button and the starter motor whirred it's heart out with no fuel pump whine and not a sputter from the engine.

    Then - standing beside the bike - I unplugged the tank without jostling or even touching the tank itself and pushed the starter again. This time the bike sputtered .

    Clearly I had no spark before I unplugged the tank - and clearly I did have spark after I unplugged the tank.

    James - I absolutely agree it doesn't make sense - but it was clearly observed. Furthermore - I had a similar thng happen last week during troubleshooting - although I didn't recognize what was happening at the time.



    Here's the theory - the hot G/W wire going in to the fuel tank is shorting to ground inside the white molded plastic base of the fuel level sender. That G/W comes from the fuse panel which is fed from a G/R wire from the fuel injection relay. The ignition control unit also connects to the fuel injection relay - through the Y/Br wire and it's possible that the short is travelling to the spark box through that wire.

    I have the FI relay on my desk in front of me - -it looks good physically and the contacts don't look burned. Unfortunately - a new one is 3-4 weeks away through my local supplier and it's not cross reference-able to anything off-the-shelf.

    I spent the morning trying to agree that it's a kill switch problem and that the lights on the dash could somehow stay on even though this switch was failing - but I just couldn't get there. Furthermore - the starter button works just like normal and if there's one thing that won't work without a good kill switch - it's the starter button.
    You're quite right that a working start button eliminates the kill switch as the fault. The dash light behavior apparently changed sometime between 1987 and 1991.

    The fuel sender is quite possibly at fault. (I assume that's the part you ordered? And you also ordered the o-ring, right?) I believe I mentioned that on page 3, in connection with my issue.

    Your observation of unplugging it and having spark return certainly strongly suggests problems with the sender, and replacing it is a reasonable next step. The theory of a sender ground fault traveling to the ignition box through the FI relay doesn't work, though, unless the relay is damaged. The ignition box is connected to the other side of the relay, the coil side. The yellow/brown wire from the relay to the ignition box is the relay coil's ground. The green/red is the switched power coming from the relay. The fuel pump power is not on a common circuit with the ignition box.

    Here are some tests you could do to assess the sender itself, without taking it out of the tank. (If you take it out, you can test it more directly as well.)
    1. To see if the green is shorting to ground, disconnect the fuel pump and put a multimeter in continuity test mode on the connector's pins for green and brown. Manipulate the cable up near the white plastic bit. If it's shorting to ground, your meter should blip when it shorts.
    2. To see if ground is failing (e.g. the weak solder joint), set your multimeter to measure resistance attached to the same two pins, and clip the yellow and black wires to each other in the tank (or bring them outside the tank if there's fuel around). Resistance should be zero, of course. Manipulate the cable some more, and see if resistance jumps up at any point.
    3. And, of course, you can similarly measure resistance while manipulating the cable with the meter attached to the green pin & yellow in-tank wire, then again on the brown pin & black in-tank wire.

    I'm interested in what you find here, because it may well be the same issue I'm having. I've resisted ordering a new sender because it's the most expensive of the current potential culprits (except the HES).

  4. #49
    Registered User jwetering's Avatar
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    Hey James;

    Yeah, I thought my theory would fail because of the reason you describe. I should replace the relay as well but the chance that both parts have failed is pretty slim isn't it?

    I ordered a sender because its cheaper than an ignition box, fi computer, or hes. There's lts of expensive parts I could replace.

    I took the old sender out of the tank last night and performed your test 1. That turned out fine. I'll try test 2 and 3 tonight.

    B@stard thing.
    jasper
    north vancouver

    1990 K75S

  5. #50
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    Hmm, come to think of it ... my intermittent issue started only some time after my original sender failed completely (no pump operation at all), and I replaced it with a used one. Hmm, indeed. This may have moved up on the shopping list.

  6. #51
    Registered User jwetering's Avatar
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    Well - you're right James. Upon inspection it is not possible (or at least very unlikely) that a bad sender is causing a loss of spark.

    A bad relay could do it though...couldn't it?

    If the coil was shorting circuiting, that prevents the fuel pump and injectors from getting power but also shorts out the power to the coils.

    I want to find a relay tomorrow.
    jasper
    north vancouver

    1990 K75S

  7. #52
    Registered User jwetering's Avatar
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    Update:

    I found the relay I need at my local BMW store. The Fiche posted at Max BMW is misleading at best and plain wrong at worst. Looking at the Fiche - the part in question is #15.

    The relay I pulled off of my bike was marked with the number 1459 574.3. This part is black in colour and doesn't show up on the Fiche. It is stamped BMW though and has 5 pins, with the two 87 legs making when the coil is activated. According to the schematic - one leg powers the fuel pump, the other leg powers the injectors.

    Notably - the hot wire for the coil comes from the kill switch and it is grounded through the ignition box. This is where I think my problem is.


    The part I bought is 61 36 8 373 700. This is described in the Fiche as "RELAY, MAKE CONTACT, WHITE GREEN" and the notes call it "LOAD SHEDDING".

    It is green in colour but it is the same as the relay I pulled out - 5 pins, the two 87 legs make simultaneously when the coil is activated.

    It will work!



    Later in the Fiche, for part #15, they specify 61 31 1 459 675 "RELAY - ABS/OFFNER/BLUE" with a note that says "ONLY APPLIES TO FUEL INJECTION SYSTEM"

    This relay doesn't exist on the bike and the photo shows a four pin relay which simply wouldn't work in that application.

    What a mess!



    I have a new fuel sender on the way as well.

    I'll install all of this on Saturday - and I have no doubt it will run. The question is for how long.

    Attached Images Attached Images
    jasper
    north vancouver

    1990 K75S

  8. #53
    K75RT Keith
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    I'm sure I missed your response, Have you replaced the connector for the fuel pump and gauge? Yes, I realize that it should have no effect on the rest of the electrical system. However, lets say that after you replace the FI relay, HES, brain, clean the starter armature at the brushes and cleaned all the grounding points you still have the same problem and get the same result from wiggling the connector. Might it be a wise investment to replace the connector now and remove that from the possible problems. The other possibility is a fault in the waring harness.
    Last edited by KKELLER149854; 05-20-2013 at 03:46 AM.

  9. #54
    Registered User jwetering's Avatar
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    The new fuel sender comes with a new connector of course, so that half is done.

    Need to be clear here...I *never* could cause the fault to occur by wiggling the connector, or by doing anything in fact.

    I twisted and shook and wiggled every connection on the bike a dozen times. I used my multimeter on all of the suspect connectors while shaking twisting and wiggling. I never made the fault appear.

    The fault came and went randomly. Never while I was testing connections. The fault came and went before my eyes without me even touching or moving anything.

    We'll see where it goes. For what its worth...the bike felt great on the latest test drive. I replaced the fuel sender and the FI relay. No reason to believe this would change how the bike performs, but it felt smoother.

    Thanks again for the support guys.
    jasper
    north vancouver

    1990 K75S

  10. #55
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    I seem to remember that a couple of the relays in there are interchangeable. I just don't remember which.

  11. #56
    Registered User jwetering's Avatar
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    Well, that didn't turn out great.

    I took the bike out on Monday (my birthday) with a plan to tour around the city a bit. I got as far as the crest of the bridge by my house and it died. I got about 5 kilometres - right at the point where I turn my choke off. Warmed up but not hot.

    This is now a predictable event.

    I coasted to the bottom of the bridge (its a big six lane crossing) and parked on the side of the road.

    All the dash lights are on. The starter whirrs away - but no movement on the tachometer. The schematic says that the tach runs off of coil #1

    I unplugged and replugged the tank. Nothing

    I unplugged and replugged the ignition box. Nothing.

    I unplugged and replugged the Hall Sensors. Nothing.


    So I coast to a parking lot of a local park and take a 15 minute walk. I return to the bike - it starts up. But I only get about 1 kilometre into a residential neighbourhood when it stops again.

    This time I park it and take a 1.5 hour walk. I even treat myself to a birthday Frappuccino along the way (happy f*%^$ng birthday).

    When I return - it fires right up.

    I ride it the 6 km home and immediately order up a new Hall Sensor plate from Euro MotoElectronics for $380. It will be here Thursday.

    For all you guys just about ready to post and say "I told you so"....Don't - just don't.
    jasper
    north vancouver

    1990 K75S

  12. #57
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    Jasper,
    Sorry to hear that. It really sucks, especially on your birthday.

    David Sword

  13. #58
    Registered User jwetering's Avatar
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    I just returned from a 400 mile tour ride with a group of mates. The K-bike ran flawlessly.

    Let the record show that 19 minutes after I made my very first post - KKELLER suggested that my problem could be the Hall Effect Sensors (HES). This was echoed by Paul Glaves soon after, and then Don Eilenberger and pretty much all the people we should be listening to.

    Now - I didn't ignore that good advice - in fact I did a little more research and decided that yes indeed, the symptoms I had did indeed indicate faulty HES. The problem was that my bench test let me down. I could not reproduce the failure on the bench and I mistakenly believed that this confirmed that the HES were not my problem. That led to a wild goose chase where the wild goose was my tail. I did manage to clean up my grounds and learn a whole lot about how the bike works - so that's always good.


    Long story short future readers of this thread - if you have no spark and no fuel pump then the Hall Effect Sensors are very likely your problem....they may even test ok. At $400 it's not cheap, but it's not expensive either. I would stop short of suggesting you replace the HES in the hopes that it will solve whatever problem you are having - but as was pointed out in this thread...the HES is likely to fail at some point anyway so it's not wasted money.

    My bike has 60,000 mile son it by the way.

    Thanks to all of you for your help and support.
    jasper
    north vancouver

    1990 K75S

  14. #59
    A bozo on the bus deilenberger's Avatar
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    Jasper,

    Thanks MUCH for bringing the thread up to date.. too many times people ask questions, get suggestions and never let us know how it turned out (as Paul Harvey used to say "The rest of the story..")

    Glad to hear the problem is solved, and enjoy your K75S.. it should go another 20 or so years before needing this again..
    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

  15. #60
    3 Red Bricks
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    Jasper,

    It's possible that the problem with the bench testing of the HES was the "bench".

    Every previous testing of the HES that I have heard of was done in the bike with the bike running. The hot engine is transferring heat to the HES and the added heat from the hair dryer causes the symptoms to appear. On the bench, the HES is in open air and allows heat to quickly dissipate to the the air. While surface tempratures on the HES may have appeared sufficiently hot, the internal electronics may have not been sufficiently heat soaked for a long enough time to cause the failure to appear.


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

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