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Thread: Failing Fuel Pump R1100RS

  1. #1

    Failing Fuel Pump R1100RS

    Seeking guidance on possible fuel pump failure on the '94 Oilhead. Has been dif' to start recently and when it would start the exhaust was noticeable of smelling of gas. Won't start now, fuel pump not heard pressurizing when ignition key switched to start position. Checked fuse and swapped out relay under seat but still no fuel pump action. Pin connectors secured. So it would seem that the Fuel Pump had died but first before I lay down heavy dollars by ordering a replacement I am woundering it there is a way that I can readily check the fault being at the pump, any other guidance will be appreciated, thx! Bill

  2. #2
    Registered User roger 04 rt's Avatar
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    Remove the fuel pump relay and jumper pin 3 to pin 5. The pump should immediately come to life.

    You could also try separating the fuel tank connector and reseating it a few times.

  3. #3
    Remove the fuel pump relay and jumper pin 3 to pin 5. The pump should immediately come to life.

    You could also try separating the fuel tank connector and reseating it a few times.[/QUOTE]

  4. #4

    RE: R1100RS possible fuel pump failure

    Thx for the response. I had removed the F.P. Relay and used known good alternate relay in its place, still nothing coming to life concerning audible pressuring up from the pump, conclusion is that the original relay should be good. #6 push-fuse is also good. When place the ignition on the start position I ear a subtle click from the relay bank this also suggest the relay is good? Disconnected/reconnected the harness from gas-tank to relay connection. If I've completed a thorough tracing of problem areas then yes of course the pump must be bad but there may be more to consider looking at then I know so picking out the info' from you peoples. One additional question is concerning micro-fiches showing 2 fuel pumps, one being a "Suppressed" pump and the other pump is simply referred as a Fuel Pump. Which one is the correct for the '94 and then also how many M.M. is my correct size? I see that there are several of different M.M. sizes for example a 37mm and a 43mm?

  5. #5
    Registered User
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    If you do the test Roger suggests, that will test the whole circuit EXCEPT the relay control section. It will give you alot of information to help solve your problem.
    As well as re-seating the Fuel pump/gauge connector, to try to improve electrical conductivity, you could jump 12v directly to pump side of the plug and see if the pump fires up then. ( Be careful you get the right terminals. )
    Steve

  6. #6
    I am sure somebody can help me out here, but how in the world would a "failing" fuel pump - either not pumping or pumping at less than robust - cause a rich condition and the smell of excess fuel.

    I think we have either a fuel pressure regulator issue (very rare) or an intermittent spark issue causing incomplete combustion.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  7. #7

    Re: R1100 Fuel Pump Issue

    P.Glaves: > I am sure somebody can help me out here, but how in the world would a "failing" fuel pump - either not pumping or pumping at less than robust - cause a rich condition and the smell of excess fuel.

    I think we have either a fuel pressure regulator issue (very rare) or an intermittent spark issue causing incomplete combustion.

    Thanks once again for then responses and guidance to help me ensure that I have an actual fuel pump failure(which I assume is the simple answer since it doesn't activate with ignition switched on parked). Prior to ordering the expensive replacement parts I want to examine anyother perhaps less likely but worthwhile taking a look at the associated electrical circuitry.
    Responding to Paul looking for someone to perhaps set him straight(copied and pasted quote(: '), I simply attempted to post all my observations prior to the suddenly silent fuel pump and perhaps I supplied to much in that regard? Nest step in my garage is see if the pump will jump start with 12V added thru' the pin connector but not certain on the pin numerical designation sequencing i.e. beginning from L>R or R>L and row IOT ensure I touch the correct pins? Perhaps that can be found buried in my Clymers somewhere? Yes, you would be correct that I have not much of a grasp on Oilhead circuitry(yet).

  8. #8
    MOA #24991 Pauls1150's Avatar
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    It's a '94 ... has the HES been upgraded? One trigger controls the injectors, the other controls the ignition...

  9. #9
    Registered User dieselyoda's Avatar
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    I think you should go back and start at the beginning.

    Fuses, all of them, pulled, checked for corrosion, checked for continuity. Check and make sure you have good grounds.

    Determine if the engine won't start because of lack of fuel, lack of spark.

    The fuel smell complaint leads me to agree with Paul Graves and Pauls1150 that you are chasing a ghost when you don't hear the fuel pump.

    Make sure that while you are doing all of this, your side stand is up.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  10. #10
    So is the issue hard starting and smelly exhaust? Or is the issue the fuel pump fails to come on?

    As for the HES, if it has never been replaced or rewired it is on borrowed time. BUT, when the key and kill switch and the sidestand switch are all first "on", the Motronic runs the fuel pump for a few seconds and then turns it off. Thereafter it is the signal from the HES to the Motronic that keeps it running. So, if it fails to come on with switches (ignition, kill, sidestand) on, then that is either a switch issue or a failed pump, or a failed Motronic.

    Go back to Roger's test - apply power directly to the pump at the relay socket as described.
    Last edited by PGlaves; 10-13-2017 at 08:17 PM.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  11. #11

    Re: R1100RS Failed fuel Pump?

    Again thanks for the guidance especially for electrics check, I'll be getting on top of all that prior to shelling out for a replacement fuel pump. I'm wanting to ask those of you to share any actual knowledge of the "Aftermarket Replacement Fuel Pump" applicable per BMW Part# to replace onto my '94 model year(https://www.beemerboneyard.com/16141341231rk.html). Sorry guys but not going to use BMW however doing some research on the replacement pump specs it does not seem to have the pressure and delivery capacity compared to BMW and is actually smalerl in diameter and length. Give me a heads-up for if using this is not going to compromise the performance. Bill

  12. #12
    Pepperfool GSAddict's Avatar
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    Ufda happens..........

    Need your R11xx Hall sensor rewired? PM me.

  13. #13
    Day Dreaming ... happy wanderer's Avatar
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    Somebody posted this company a while ago and said they had good success with this pump:

    https://www.highflowfuel.com/i-23899...1992-2006.html

    I ran the beemerboneyard replacement pump in my 96 RT for years before selling the bike. Still in the bike as far as I know. BMW pumps are over rated and over priced. You will sometimes have to change the connectors from ring to push on or other so a bit of minor fiddling is sometimes required. No big deal and very easy to do.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  14. #14

    Re: Falling Fuel Pump R1100RS

    Been awhile since I've followed up on my issue with you generous people, here's what I have done to reach ultimate success!
    I forgo'd temptation to run actual circuitry and component diagnostics deciding to follow a path of "least resistance" based on the almost predicable failure of a fuel pump on models such as mine and that when switching the ignition I could hear the relay switch ready to go. Being satisfied that the cost of an alternate manufacture pump kit was savings enough to venture on a probability that I indeed have fuel pump failure. I went with the replacement kit from "Beemer Bone Yard" and includes pretty much all that's needed but with some splicing required for converting from BMW ring type pump connectors to spade type using barrel coupling connectors and shrink tubing over them, I also discarded the plastic flexible replacement external replacement fuel lines for "Fuel Pump Grade" rubber lines. If I had to sink what BMW is asking fuel "Just a Fuel Pump: and then the needed peripheral parts, I'd have defiantly explored the electrical pathways before such an investment rather I considered that with a total investment under $175, using the "BoneYard" product kit, if I was wrong then at least my bike would have the renewed fuel delivery set-up once I solved a circuitry or component path issue giving me one less potential trip inconvenience to be averted! Having removed the fuel pump plate with affixed assembly I snipped, crimped, and shrunk the =/- wires discovered shortly into it that a 3rd wire passing thru' the plate has separated from somewhere it had been soldered to, being that it was on the internal side and a very stiff contour it was easy enough to find the detached end's home to be a solder onto a plastic component pressed into the plate containing a thin piece of conducted metal embedded, this was part of the fuel level sensor and although I'm not certain whether it were to have anything to do with the pump itself I did still did not know if the wire came loose while in the tank or during removal of the plate and innards out of the tank that requires some precise angles to not damage the float arm, I doubted it had been separated at the solder while still in the tank as I had no low fuel warning light faults when the bike last ran low? I repaired the solder connection and proceeded with the installation of new pump, filter, fuel-lines and clamps and reinstalled into bike then added the fuel to the now mounted connected tank and now can report a happy ending! One side-note concerning the smell of gas I remarked on, I found that one of the twin vent tubing fixtures underneath the plate was clogged, which I cleaned then, do not know if that in-of-itself could have been allowing vapors to be trapped causing an aroma but now have replaced all lines. Its been raining here and not yet had opportunity to take it out of the garage, maybe tomorrow?
    Thanks again to the "Tech-Know-How Support", apologies for not taking a more technical use of your contributions but having read them thoroughly I feel that I have a better understanding of the electrical side of the fuel delivery system/at relay relationships work, another little bit of knowledge added to my confidence to venture away from my home on an aging machine.

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