Fuel Pump Relay dying.

Discussion in 'GS Boxers' started by watchmen, Dec 20, 2012.

  1. watchmen

    watchmen Been here awhile

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    So tonight my R1150GS died on the freeway on ramp. This is my favorite on ramp in town, its a little less than a 1/4 mile until it hits the freeway. I was at about 6500 rpm in 1st gear and it spurters off on me. I rarely rev the bike that high in first, but this onramp is an exception. The same thing happened about 8 months ago about the same area but that time i was in 4th gear. Luckily it only took a few minutes to fix and I just swapped out the horn relay for the fuel pump relay and it started up like nothing happened. But it makes me wonder why my fuel pump relay died twice in the last year.

    Any reason why my fuel pump relay would blow twice in a year? It doesn't help that it blew at the same area both times.
    #1
  2. Multiplicity

    Multiplicity Been here awhile

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    Relays don't blow. There are a few different failure conditions.

    First. If you swapped the horn relay with the FP relay, did the horn still work. You swapped one old relay for another old relay. Relays can die from age. The contacts can get corroded or even burn if the FP has a high amperage load.
    The first thing to check would be corrosion in the terminals. Check for a ground problem. You should currant ramp the FP too. Most likely it's a ground or connection issue, but the pump could be at fault too. Voltage drop test the power feed and the ground circuits. Also make sure the control signal is within spec. My monies on a high amperage FP :norton
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  3. vagueout

    vagueout Long timer

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    Did you confirm on both occasions that it was the relay that failed?? From the info you give i'm thinking fuel flow or lack of, hence i would suspect fuel filter, condition of fuel hoses or the condition and quality of the pump itself. But then again your favourite on ramp may be smack in the middle of a "bermuda triangle" of relays. The truth is out there. (where have i heard that before)?:eek1
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  4. KShow

    KShow Been here awhile

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    I just had a similar issue, bike would die, wiggle stuff around and it would restart most of the time. Turned the fuse to the motronic was bad, it didnt look like it, and the meter would show it was good. There was a hairline crack in the exposed wire that runs across the top of the fuse between the blades, had to look real close to see it. . replaced it with a regular automotive type sealed fuse and the problem was solved. Took a bit of headscratching after I dismissed the obvious to realize that the problem was the obvious.

    If it happened in the same place both times, Id look for people wearing tin foil hats around there, they might know something you dont about that particular area:lol3
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  5. def

    def Ginger th wonder dog

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    Coronal mass ejection. Your cell phone is next, then your TV.
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  6. Warin

    Warin Retired

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    A large percentage of electrical problems are connectors, replacing stuff just disturbs the faulty connection.

    When you swapped the relays - you wiggled stuff around.

    Check the connectors that go to the relay. Also check the wire connections to those connectors of the relay.

    Wiggle stuff around and see if you can get the bike to stop running.

    Good Luck.
    #6
  7. watchmen

    watchmen Been here awhile

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    I never updated this topic, but the relay ended up working in the horn area. When this happened a year ago, the relay wouldn't work in either. This time I cleaned out the contacts on the relay with a scotchbrite pad and it worked great in the horn area. I've been meaning to check all the connections to the fuel pump relay, but I haven't done it yet.

    Thanks for all the help guys.
    Now I just need to wrap my helmet in tinfoil when I get on that on ramp.
    #7
  8. vagueout

    vagueout Long timer

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    Flux capacitor???:*sip*
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  9. Scapadu

    Scapadu Motomaniac

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    As the pump relay is also the one that electricaly feed the fuel injector, is there anyone able to say if during the "Overrun Cut Off" sequences that relay is released or if it is the Motronic only that stops the Fuel injections?

    PS: the Overrun Cut Off happens when the throttle is fully closed and your engine still over 2000 rpm (i.e when decelarating).

    The reason for that question is the fact that i had a month ago some engine cuts when decelarating, where the engine took 1 or 2 sec before it restarted once throttle were back open, sometime where the engine completely died, but restarted normally once stopped.
    This happened only during decelaration ( 5 times over 800km), never when at iddle speed or during acceleration.
    HES was new and working fine, TPS was at 0.36v, gas filter was new replaced, gas pump running fine and hosing ok.
    I did the same swap than above (horn relay with pump relay) and it never happened again.
    So it looks like it was the relay but why only during Overrun Cut Off sequences?

    Thanks.
    #9
  10. Scapadu

    Scapadu Motomaniac

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    It looks you never get a better help than from yourself. I ask the question to the main wrencher at my dealer.
    The answer is yes, the motronic releases the fuel pump relay during the "overrun cut off" sequence.

    BTW, i have done 500km since i swapped the relay and the engine cut did not come back. Problem seems to be fixed. :D
    #10
  11. roger 04 rt

    roger 04 rt Long timer

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    Hi scrapadu,
    Just saw your post for the first time. Back last year I did some testing of the overrun fuel cutoff sequence, posted HERE.

    Your about right on when it kicks in but the actual numbers for the R1150s are: throttle less than 2 degrees and RPM greater than 1800 while decelerating. During that time, the fuel pump does not stop running, the guy you asked is wrong. To confirm it I just went back through a large file of GS-911 data and looked at the fuels pump setting during all modes and it never is turned off once the motor starts.

    But due to lack of any fuel from the injectors, the motor is "stalled" during the overrun fuel cutoff interval. When it reaches 1800 the engine " restarts" in a rolling restart manner and you can feel the engine come back to life. You can keep that bump at 1800 from feeling like a surge if you crack the throttle just a bit (2 degrees or more) before it the deceleration reaches 1800.

    Hope that helps,
    RB
    #11
  12. Scapadu

    Scapadu Motomaniac

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    Thanks for your interresting feedback. However if you are right i do keep with my question raising.
    Why did the engine cuts happened after a overrun cut out sequence each time and why the fact that i changed the relay did solved that problem?

    First thing i will do may be is to swap back my relays and see if the problem comes back again.
    Next step, i do not know for now, but will think at it.

    Thanks again anyway.
    #12
  13. Multiplicity

    Multiplicity Been here awhile

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    I don't how your bike is wired, but if the relay is bad it could also be a physical relation to it loosing it's
    ability to control output to the pump on decel. Inertia might be why it only happens on decel. All decel fuel control is done through the injection system, not by turning off the pump. I've had relays flake out with minor voltage changes. I even had one that would only fail when the brakes were applied. A voltage threshold could be why yours is/was acting the way it did. A drop in system voltage when the RPM's drop, coupled with the load from the brake lamp could be all it takes. You removed the suspected relay and installed a known working one and the problem has stopped. Could be you disturbed a faulty connection too. To many variables to know why without failure duplication while monitoring input/output signals :norton
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  14. roger 04 rt

    roger 04 rt Long timer

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    I can say with certainty that the fuel pump stays running, and that the Motronic sets the injector times to zero during OFC.

    Your explanation of a voltage drop during OFC is interesting, certainly a possibility. During OFC, the engine is stalled! It is firing the spark plugs, but not injecting any fuel. So more than semantically, its not running, just being pushed by the rear wheel.

    If you were in OFC, say decelerating from 5000 RPM, and at 2500 RPM pulled in the clutch, the engine has to catch with very little rotating inertia--only what is has from its own mass, the rear wheel isn't driving it. I'll have to try that today when I'm out riding.
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  15. roger 04 rt

    roger 04 rt Long timer

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    Your question is a good one, but I don't have an answer. I'll think about it and try it on my bike. I'm going to try OFC from 5000 RPM and pull the clutch at the last moment before the injectors restart and see what happens.
    #15
  16. Multiplicity

    Multiplicity Been here awhile

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    It would be nice to know at what RPM it actually dies at. That would help paint a better picture :1drink
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  17. roger 04 rt

    roger 04 rt Long timer

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    That's true. Since under Ofc the engine is off till 1800 RPMs, did it come back on and stall or never restart?
    #17
  18. Scapadu

    Scapadu Motomaniac

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    I will probably subcribe to that possibility and i will tell you why.
    Several time the engine cut did happened, and i should say the more often time it happened, i was having the heated grips on. Matter of fact, as i noticed that, i did wonder what kind of relationship there could be between the engine cut (and fuel pump relay) and the heated grips and thought this was just co'incidences.
    FYI my batterie is relatively new and in very good shape (motorbike sleeping in a warm garage).
    But now with your explaination it could have happened that due to a bad relay connection and the heated grips on, the relay released itself because of a too low voltage during deceleration.
    Now, because i have worked on the relay (swapped) it is possible that the loose connection has wanished and i can no more reproduce that failure again.
    To tell the truth this is the best scenario i have seen for now on that failure and i really like it. All facts are matching together, deceleration, OFC, fuel pump relay released, heated grips on, engine cut.
    BTW, the iddle speed of my engine is low, only 1000rpm, it works perfect but may be i will raise it a bit to 1100rpm. I mentionned that because it happenned once, that i had an engine cut while engine was at very low rpm, but with heated grips on :wink:.

    Thanks a lot guys for your experiences :clap , which i think, put me on the good track for getting the clue (knock the wood :D ) .
    #18
  19. Scapadu

    Scapadu Motomaniac

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    For what i am concerned, i fact it was not a true full engine cut in most cases but the fact that when reaccelerating after decceleration and with rpm between 2500 and 3000 the OFC did not stop and engine did not restart at once but after 2 to 3 secs. However it finally always restarted while it still was above 1800rpm.
    The only case where the engine completly died, i was not really more on deceleration but at very low RPM, most probably below 2000rpm.
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  20. roger 04 rt

    roger 04 rt Long timer

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    You've got an interesting intermittent problem.

    While decelerating, even in OFC, the engine RPMs are high (above 1800) so your alternator should still be putting out full power.

    I doubt it is your problem but BMW changed the panel warning light for the Alternator from 1.7W to 3W. The reason I mention this is because at low RPMs and just after starting, it is this Batt/Alt warning light that provides the field current to the Alternator to start running. On my 1150 I noticed that after starting the Batt/Alt light wouldn't go out until I blipped the throttle and increased the RPMs. That left the voltage low after starting, which led to the injectors putting out about 10% less fuel at cold idle until the Batt/Alt light went out.

    In my case the Hi Beam bulb was 3W, the Batt/Alt was 1.7W so I just swapped them, problem solved.
    #20