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Thread: 1997 BMW R850R Sudden No Start - Not Just the Hall Sensor!

  1. #31
    Pepperfool GSAddict's Avatar
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    I agree with Anton.

    Remove the lower line on the tank and deadhead with a pressure gauge that has a 150psi range.
    Cycle the pump for the 2 sec start cycle.
    If all is good tank side you will read up to 120psi (the pump has it's own built in internal over pressure regulator)
    Report back
    '
    Ufda happens..........

    Need your R11xx Hall sensor rewired? PM me.

  2. #32
    Neglected Bike Adopter
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    Quote Originally Posted by GSAddict View Post
    I agree with Anton.

    Remove the lower line on the tank and deadhead with a pressure gauge that has a 150psi range.
    Cycle the pump for the 2 sec start cycle.
    If all is good tank side you will read up to 120psi (the pump has it's own built in internal over pressure regulator)
    Report back
    When I first used the testing kit, I was using a T-fitting plugged into the lower line, not a dead-end fitting. I also blew compressed air into the gauge to make sure it would actually read pressure after I got none at the line.

    I'll rent the tool again and test with a dead-end fitting. It makes sense that I wasn't testing pressure directly from the pump with a T-fitting; what I suspect is that this cheapo pump just isn't providing enough fuel pressure, or enough flow, to run the bike now, and never provided enough to run the bike correctly anyways.

    Anton -- I never tried to block the "send" line but I did get what looked like plenty of flow from it into a container when testing, so I'll try to block it off with a pressure gauge as GSAddict detailed.
    Owner of the saddest 1997 R850R you ever did see.

  3. #33
    Neglected Bike Adopter
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    Smile

    I have very good news -- the bike runs again, and seems to be running properly this time!

    Here was the process: I dead-ended the fuel "send" line with the rented pressure gauge again as you folks suggested. Surprise, surprise -- 0 PSI from the cheapo fuel pump. I even tried draining the gas out of the tank via the fuel pump and only got a very slight trickle of fuel out of the send line.
    Long story short, I swapped in the used OEM pump I had and it fired right up.

    All these parts swaps and work, because of a bad fuel pump with less than 60 miles on it! My guess is the pump gradually started failing the moment it went in the bike.

    I then did a relatively quick throttle body synchronization and idle adjustment with my dad's Carbtune. The bike still seems to vibrate quite a lot whenever the engine is running, which increases directly with engine RPM. I still have yet to drain the somewhat overfilled oil and do a valve adjustment so both are on the list of things to do very soon. After those I plan to do a very careful TB sync. Any other ideas as to what would cause it to have what feels like rotary or lateral vibration?

    Also the low fuel light seems to be half-lit all the time, which is odd. Not sure if I blew the relay again or if maybe I got the float stuck when I replaced the pump. I'm going to look inside the tank again with a snake cam and figure it out.

    Thanks for all your help, GSAddict and Anton. At the very least I can now use this machine to get places while I slowly work out all the other less important issues.
    Owner of the saddest 1997 R850R you ever did see.

  4. #34
    Pepperfool GSAddict's Avatar
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    '
    Ufda happens..........

    Need your R11xx Hall sensor rewired? PM me.

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