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Thread: 1990 K75S died suddenly

  1. #16
    Registered User jwetering's Avatar
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    Just saw the recent posts guys - I posted my test experience before reading them.

    I agree working in the parking lot at work is less than ideal. I think tomorrow I'll button it all up, cleaning connections as I go and start riding it home. I'll take the backroads where I can and if it stalls, then I park it, wait for it to cool down and carry on.

    D@m% b!t&h p*&c% of s^@#t
    jasper
    north vancouver

    1990 K75S

  2. #17
    3 Red Bricks
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    If the problem is not the HES, then it probably is not temperature related. It probably is an intermittent connection. The fuel pump circuit is one of the more common non-heat related areas of intermittent contacts that will cause a bike to suddenly stop. Unfortunately, waiting for it to cool down may not cause it to remake contact.

    You might be safer to rent a cheap U-Haul trailer and insure you make it ALL the way home.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  3. #18
    Registered User jwetering's Avatar
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    Quote Originally Posted by 98lee View Post
    If the problem is not the HES, then it probably is not temperature related. It probably is an intermittent connection. The fuel pump circuit is one of the more common non-heat related areas of intermittent contacts that will cause a bike to suddenly stop. Unfortunately, waiting for it to cool down may not cause it to remake contact.

    You might be safer to rent a cheap U-Haul trailer and insure you make it ALL the way home.



    All good points Lee - and thanks for sticking with me.

    I did notice this morning when it died that I had no spark while I cranked. (100% confirmed).

    If the fuel circuit is somehow failing me - could this also cause no spark?

    Also - do I understand correctly that the fuel pump is supposed to come on with the key - or only when the starter is pushed.

    I know these things are interlocked all over the place.

    thx.
    jasper
    north vancouver

    1990 K75S

  4. #19
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    On 2 valve Ks. The pump does not come on with the key. It should come on for a couple of seconds once you press the start button (enough to get the bike running). Once it senses that the bike is running (through feedback from the HES), the pump will continue to run.

    So it sounds like you have an ignition problem. When I get a chance later this evening, I will have a look at the schematics and see if I can come up with anything.


    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  5. #20
    Registered User jwetering's Avatar
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    Quote Originally Posted by 98lee View Post
    On 2 valve Ks. The pump does not come on with the key. It should come on for a couple of seconds once you press the start button (enough to get the bike running). Once it senses that the bike is running (through feedback from the HES), the pump will continue to run.

    So it sounds like you have an ignition problem. When I get a chance later this evening, I will have a look at the schematics and see if I can come up with anything.


    First the good news - I am arranging to bring the bike home tonight.




    I strongly believe it's a spark issue and not a fuel issue. That's based on:

    1) The suddenness of the death(s). Although this may be more intuitive than scientific.

    2) The fact that I directly observed the absence of a spark during a failure yesterday and that I directly observed a spark during a period of operation using the exact same technique (spark plug grounded against the valve cover).

    3) I observed neither fuel nor spark during the fail mode yesterday - although I didn't test positively for absence of fuel. BUT, from the schematics that I have seen, there are a few different interlocks which shut down fuel in the absence of spark. Conversely, there is no interlock which shuts down spark in the absence of fuel. These are critical points. I am assuming:

    Ignition fault -> no spark, no fuel.

    Fuel fault -> yes spark, no fuel.

    ie - In no instance will a fuel fault result in no spark.

    If this isn't true - I need to know that now!

    The bike is apart now - so it's time to test - but I have to assume that the fault will not be occurring during these tests. That's just one of the burns with intermittent faults.

    My plan is to use German Bert's troubleshooting guide to test the wires going in to the ignition box while I wiggle those wires. Then I will clean the contacts with electrical cleaner and reassemble.

    I will also check the ground(s).

    Then I will put it all together (loosely) and starts the bike ( I assume it will start).

    Then I will wiggle the ignition and kill switches and whatever other wire harness and bundle I can reach.

    Hopefully it will quit when I find a loose connection.


    Notably - Lee has confirmed that a lack of a signal from the HES will shut down the fuel (and of course cause no spark). The sensors themselves as well as the wires and pigtail may be good according to my conclusive testing last night - but I haven't yet tested upstream of that.


    Once again - thank you for sticking with me Lee.
    jasper
    north vancouver

    1990 K75S

  6. #21
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    K100RS 85 w 147k mi. NAPA CE-1 Stabilant 22 keeps mine going more than anything else

    Dear Sudden K Bike loss of power or loss of even more,

    I've "Q tipped" many low millivolt type connectors and many 12v connectors over the years with NAPA CE-1 Stabilant 22. You hear a little sizzle of the corrosion being obliterated, put the connectors together and things run better, same computer, same hall effect sensor(s), same fuel injectors, same fuel pump as new. The eye dropper bottle cost just shy of $100. It was the best $70 I spent almost 10 years ago. Mine would cut in and out, die, sputter etc. then I started using this on the K1 connector first. I have not need a tow yet. Did buy some new relays and brake light switches.

    A different motorcycle had an intermitant start one day last summer, turns out the battery connector had jiggled loose. Wires that are almost broken through can do this too, they might be near the steering triple clamp because those wires take a beating and can be routed well or poorly causing a wide range of "lifetime."

  7. #22
    Registered User jwetering's Avatar
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    Thanks for that input 075038 (if that is indeed you real name). I am thinking along the same lines that you are. It's a b@$t@rd little wire somewhere that's shorting out or broken or...

    I just got back from a stint of troubleshooting. I hooked up my timing light to lead #3 and cranked the starter. The strobe is strobing so, at the moment, it will be impossible to diagnose a fault.

    Over the next several days I will be checking and cleaning every connection I can find as I reassemble the bike.

    For instance - I could see that the primary ground is pretty corroded. I checked continuity between each of the wires and the frame though - and they all check out ok.

    Nevertheless - I will take it all apart and clean it before reassembling.

    Untill it fails - I can't really find the fault. I plan to ride it around the neighbourhood (all uphill of my house) for a full day and hope it fails....then go from there.
    jasper
    north vancouver

    1990 K75S

  8. #23
    A bozo on the bus deilenberger's Avatar
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    Jasper - it's getting late (about 1:30AM here..) so tweak me tomorrow and I'll give some more thought to it.

    Quick thoughts: If you are seeing loss of BOTH injection and ignition - the common failure point starts at the HES and works it's way up through the ignition module. The L-Jetronic gets it's trigger off the ignition module (which is triggered by the HES,) so it isn't likely to be at that end. If I had to guess, it's between the HES and the ignition module (located under the tank bolted to the frame right behind the steering head.) I would be looking very carefully at the wiring between the two (assuming your HES test was conclusive.) And Stablant-22 IS very good stuff. The tiny 10cc bottle will last the rest of your life, so the cost isn't all that awful. I talked NAPA down to around $45 for mine, but that was at least 15 years ago..
    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

  9. #24
    RK Ryder
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    In the past, I've had my K100 just die a few times while riding. My problem was much simpler than yours most likely is. Feel free to disregard it. On a few occasions, while riding over a rough road, the key in the ignition moved and shut off the ignition. That ignition assembly has since been replaced. With the new assembly, I've also had the bike simply shut off while riding. Problem, with my bike and bar risers, the tank bag sits closer to the keyed ignition and the bag and key have occasionally touched and turned the bike off. I'm certain that your problem is more complicated than mine, but just thought I'd give you a scenario that had a bike running and then turning off, and of course, starting right up again. Best of luck narrowing down the problem.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
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  10. #25
    Registered User jwetering's Avatar
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    Quote Originally Posted by Paul_F View Post
    In the past, I've had my K100 just die a few times while riding. My problem was much simpler than yours most likely is. Feel free to disregard it. On a few occasions, while riding over a rough road, the key in the ignition moved and shut off the ignition. That ignition assembly has since been replaced. With the new assembly, I've also had the bike simply shut off while riding. Problem, with my bike and bar risers, the tank bag sits closer to the keyed ignition and the bag and key have occasionally touched and turned the bike off. I'm certain that your problem is more complicated than mine, but just thought I'd give you a scenario that had a bike running and then turning off, and of course, starting right up again. Best of luck narrowing down the problem.
    This was the first thing I checked - actually I checked the the kill switch - but it is effectively the same thing here.

    My thing is that when it fails - ALL of the lights on the dash stay on.

    If it was the ignition switch - or the kill switch - or a battery lead - the lights would go off.


    I'm thinking along the same lines as Don. It's the HES or the ignition box - or the connection between the two.

    The HES test was pretty conclusive....I could not get it to fail on the bench no matter how hot I got it or how much I jiggled the wires. Of course, the problem is intermittent so I can never be 100% certain - again there's the painful part of this.

    Also - I don't know conclusively that the fuel stopped. I only think it did. I didn't have a chance to check it when the failure was occurring and it hasn't happened again. What I observed was:

    1) No fuel smell out of the tailpipe while cranking the starter while the failure was occurring.

    2) No fuel fog blowing out of the spark plug hole while cranking while the failure was occurring.

    3) Yes fuel fog blowing out of the spark plug hole while cranking while the failure was not occurring.



    If I am getting neither spark nor fuel then this suggests that:

    1) The HES is telling the ignition box that the bike is not running, or

    2) The ignition box isn't getting 12V, or

    3) The ignition box isn't getting ground, or

    4) The HES is not getting 12V from the ignition box, or

    5) The HES isn't getting a ground from the ignition box.

    If I am getting fuel but no spark (which may be happening, but frankly isn't likely because the ignition box controls the EFI) then:

    1) The coils aren't getting power to the primary circuits.

    It isn't (can't be) a coil failure because there are three coil. The bike isn't stuttering or missing - it' stopping dead, and the three coils aren't all dying at the same time and then coming back to full strength soon afterwards.

    They share a power source though....and I'll be checking that as well.

    This sure would be a lot easier if the bike was failing reliably. It's all just hypothetical while it is running normally.
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    jasper
    north vancouver

    1990 K75S

  11. #26
    Registered User jwetering's Avatar
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    Well - not sure what to say.


    I haven't had much time to look at the bike over the last few days - I'm working on a Masters degree and I have a fairly significant paper due this weekend. I have work commitments and young children as well. At least my wife is a good woman and the weather is turning nice here. It's not all bad.




    When last we met, the tank was off and I had all of the wiring in front of me. The primary ground looked not great - but not catastrophic either. I had a timing light hooked up so I could see if I was getting a spark without having to pull the plug. I was - the fault was not occuring.

    Anyway - I spent this morning wiggling wires trying to make the failure occur. I hooked up my timing light and watched it strobe away when I hit the starter button no matter what I did.

    I also checked rechecked and checked every single ground wire I could find again and again - mostly on the loom going in to the ignition box. All this while jiggling and shaking and pulling on the wires.

    The strobe just kept strobing away like there was no problem at all.

    So then - I bring out some long hoses and hook up the fuel tan on a bench next to the bike (see the photo). Plugged in the tank and started the bike.

    I ran it like that for 30 full minutes. At one o=point I measured a water temperature saw 80 using my infra-red pistol.

    So I took out a a socket and ratchet and started loosening the ground bolt - just as the electric fan came on by coincidence (red herring).

    I got about three turns out when the bike died.

    I tightened the bolt again - and it wouldn't start! Could that be it?

    I checked for ground at the loom to the ignition box (there are two) and they checked out fine....ok.

    Nevertheless - I disassembled the ground screw and the five wires that are attached there. I cleaned every one with 220 grit and reassembled the whole thing with conductive paste. I hooked up the strobe - I'm getting spark.


    Here's where it gets stoopid.

    I put the bike back together again - I install the tank and the fuel lines and the vent lines and I plug in the fuel tank. I'm going to take a ride right?

    Nope - I go to start the bike and - no fuel pump whine, no start.

    I hook up the strobe - *NO SPARK* OMFG !



    So I pull the tank off again - this takes a few minutes - and try the strobe again - and sure enough I HAVE SPARK again.!!

    SO I check to make sure I'm not pinching any wires - I'm not - and I put the tank on again.

    This time it starts and runs fine.

    I just finished riding it around my neighbourhood for 20 minutes and it didn't skip a beat.


    I don't know guys. It's driving me crazy.
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    jasper
    north vancouver

    1990 K75S

  12. #27
    Registered User jwetering's Avatar
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    Eureka

    Ah - the eureka moment. Gotta love it.

    The bike had been running fine for a couple of hundred miles but tonight it stranded me again....in waning light and without tools since I'd stopped carrying them around everywhere just last week.

    It started once right after it failed - but died again real quick.

    I lifted up the tank and got my hand under there and wiggled wires while I tried to start it - no dice.

    Then I started wondering if the fuel pump was running or not - it's hard to tell with all the noise so I decided to unplug the tank and listen for the *absence* of a whirring noise.

    You know what - it fired up and burbled for me! With the tank unplugged ! Obviously I was getting spark at that point.

    Then I plugged in the tank - it fired up and I rode it home.


    ****

    So - Apparently a fault in the fuel system *will* cause a lack of spark. Not sure what the feedback loop is there.

    I'm going back up and reading the threads on the fuel sender. I can see that the wiring for the fuel pump goes through it.

    Could it be the fuel pump relay or the fuel injection relay guys?

    It seems the system reset itself once that plug was disconnected.


    I think I may have this thing beat - good thing too I've been looking and thinking about another bike and that would be a drag because I genuinely like this one.


    Will report back.
    jasper
    north vancouver

    1990 K75S

  13. #28
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    The fuel injection relay's coil appears to be grounded through pin 7 of the ignition unit. So, it seems plausible that a fault with the relay or that leg of the wiring could cause the loss of both fuel and spark.

    Edit: Of course, following that circuit a little farther -- the fact that the FI relay coil is grounded through the ignition box also means that a fault with the ignition box ground could prevent the FI relay from activating, so you may well be on the right track already.

    What "conductive paste" did you apply to the ground terminals? (Not dielectric grease, which is the opposite of conductive, right?)
    Last edited by JamesInCA; 05-14-2013 at 08:34 AM.

  14. #29
    Registered User jwetering's Avatar
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    Quote Originally Posted by JamesInCA View Post
    The fuel injection relay's coil appears to be grounded through pin 7 of the ignition unit. So, it seems plausible that a fault with the relay or that leg of the wiring could cause the loss of both fuel and spark.

    Edit: Of course, following that circuit a little farther -- the fact that the FI relay coil is grounded through the ignition box also means that a fault with the ignition box ground could prevent the FI relay from activating, so you may well be on the right track already.

    What "conductive paste" did you apply to the ground terminals? (Not dielectric grease, which is the opposite of conductive, right?)
    Thanks James.

    I used a conductive paste designed specifically for the purpose. It's similar in appearance to copper anti-seize. I am aware that dielectric grease is not conductive.

    I am sure that the ground wires to the ignition box are good. I hope that the ignition box isn't the source of the problem ($1400 from BMW)- but I don't think so given the intermittent nature of the problem.

    ***
    I'll be checking relays and the wiring through the sender unit into the pump.

    Hopefully I'll be able to *find* the fault.
    jasper
    north vancouver

    1990 K75S

  15. #30
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    That conductive paste does sound interesting, then, especially given the common failures of ground points on these bikes. Does it have a name, and is it widely available?

    I asked because it often seems as though more people than not mis-use dielectric grease for precisely this purpose, when its purpose is precisely the opposite.

    It still sounds like a connection problem. I have something perhaps similar going on, but more intermittent. The two times it's happened I've torn a bunch of stuff down, vigorously cleaned connections and replaced candidate parts. The first time it got fixed for 2500 miles; the second for several hundred miles now. The second time I didn't replace any parts, just went through a lot of connectors (and the ignition) with q-tips and a lot of DeOxit. Something appears to be fixing it; darned if I know what it is.

    If you could monitor power at the FI relay in real-time so you could see what's happening when it fails, that would be helpful. If I have to keep doing this I'll likely set up some diagnostic LEDs to show when power is flowing or not. My issue has only happened when in motion, so I can't stop and check relays.

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