CBR600 Fuel Pump again

Discussion in 'UK Motorcycles' started by Sleepy, Mar 4, 2006.

  1. Sleepy

    Sleepy Guest

    Right, thanks for the advice given in answer to my last question. Finally
    got some time to do the testing today. The result: while cranking the
    engine on the starter, battery 10.6V, supply to fuel pump 2.5V.

    Doing this is a multi-handed balancing act, so I poured some petrol into the
    carbs manually (funnel & glass jar actually) and started the engine, the
    idea being to check volts to the relay and pump without having to hold the
    starter button. As soon as the engine fired the fuel pump started working.
    A surprise to me was that its rate of pumping varied with engine revs up to
    about 4000 rpm.

    So I ran the engine until all the petrol in the carbs was gone. Cranked
    engine as before, but now the fuel pump runs. Bugger, an intermittent

    This fits, as the reason for this whole exercise was that the bike stopped a
    couple of times while I was riding it, then ran ok. Left it in the garage
    for a couple of weeks, then it wouldn't start.

    So, apart from ride it 'til it stops again, or sell it (it's bound to die
    during a test ride), any clues on what to do next? My first guess is a
    second-hand fuel pump, but budget is limited, so I can't just go buying bits
    until it works.
    Sleepy, Mar 4, 2006
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  2. Sleepy wrote
    Are you suggesting that the fuel pump only runs when the starter spins?
    steve auvache, Mar 4, 2006
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  3. Sleepy

    Chris H Guest

    The fuel pump was a known problem with CBR6's after high mileages[1]. I
    used to get occasional stoppages after filling with fuel when warm.
    Vapour lock + no fuel pump = stoppage once the carbs are drained. It had
    all the symptoms of running out of fuel.

    A 'new' pump solved it.

    Chris H,
    FZS1000, two#55
    He's predictable, but that's to be expected.
    Please remove the numbers to reply

    [1] For 'leisure rider' values of high.
    Chris H, Mar 5, 2006
  4. Cant you take the pump off and ask a local Honda dealer to check it over ,
    some of the pumps can be rebuilt
    Steve Robinson, Mar 5, 2006
  5. Sleepy

    Sleepy Guest

    No. What I mean is that when I started this round of fiddling, the fuel
    pump didn't run at all. Now, having started the engine after manually
    adding petrol to the carbs, the fuel pump runs when the starter spins and
    when the engine runs i.e. when it should.

    So now there's no fault to find.

    Given that the bike stopped itself before (and could be restarted after 5
    mins), I'd guess that it's likely to again.
    Sleepy, Mar 5, 2006
  6. Sleepy wrote
    Well yes but no. In the grander scheme of things the minuscule amount
    of fuel pumped during the half a second or so that it should take to
    start your engine is entirely irrelevant. What is important is that
    sufficient fuel is delivered to the carbs /prior/ to starting and a more
    or less continuous supply once the engine is running.

    I also really don't understand why you are so obsessed with draining the
    carbs before you start the bike.

    Almost certainly.
    steve auvache, Mar 5, 2006
  7. Sleepy

    Sleepy Guest

    Eh? I'm not (well now anyway). The only reason I ran them dry this time was
    to try to reproduce the failure situation as it was five minutes earlier.
    Except it didn't IYSWIM.

    If there's petrol in the carbs and the engine has just run, then it fires as
    soon as the starter button is pressed, leaving no time to check if the fuel
    pump was running while starting. Turning off the kill-switch disables the
    starter button too. Since it only took rev-rev-splutter-coff to do (fuel
    pump isn't connected to carbs ATM) it was quicker than removing any leads or
    Sleepy, Mar 5, 2006
  8. Sleepy

    Sleepy Guest

    Sorry, just read this bit again. My paranoia with this bit is from the odd
    time I've been caught out in traffic when running dry (bike stationary,
    engine stopped) with the petrol tap on "on", switch to reserve and spin the
    engine until it fires. Obviously a situation with other hazards, but it'd
    be nice to have some confidence that petrol is in fact being pumped and I'm
    not just flattening the battery for no gain.
    Sleepy, Mar 5, 2006
  9. Sleepy wrote
    You don't need to check if it is running whilst starting and given that
    the best tools for this are your finger tips and your ears the extra
    background noise from the starter won't help anyway.

    It disables most of the engine electric's probably.

    Really to check the pump properly it needs to be connected. You can
    test if it mostly works by simply turning on the ignition and watching
    the fuel pump over the floor but it does need to be connected to test
    steve auvache, Mar 5, 2006
  10. Sleepy

    Sleepy Guest

    No, not this one. Unlike an FI system, it doesn't start pumping until the
    starter button is pressed.
    Sleepy, Mar 5, 2006
  11. Sleepy wrote
    So you have never learnt to recognise the feel of one carb going dry and
    switch immediately to reserve? Never thoiught to look at the odometer
    and have a good guess that you might soon be needing to switch to
    reserve? You are becoming hard work you are.

    When it runs out of fuel in this way it may take some seconds before
    enough petrol is pumped into the carbs for it to be able to start, it
    also won't help if you steal electrons from the pump to do the job of
    spinning the engine with no fuel in it.
    Apart from fixing your broken sig sep you need to have a good look at
    the way you approach your ride, it shouldn't be hard work at all.

    and buy a new fuel pump.
    steve auvache, Mar 5, 2006
  12. Sleepy

    Sleepy Guest

    They're so well balanced (at tickover) that the time from this to phut is
    less than the time to get to and turn the tap. While moving no problem.
    Yes, yes, usually. But when dealing with stationary traffic I don't always
    have time to look at the odo.
    See one of my other posts: the pump doesn't pump until the starter button is

    The hazards of OE.
    £165 new, not found a second-hand one yet.
    Sleepy, Mar 5, 2006
  13. Sleepy wrote
    And this presumably is what the relay you mentioned days ago is for
    then, to supply voltage to the pump thereafter? I understand now. It
    don't seem right though.
    steve auvache, Mar 5, 2006
  14. Sleepy

    B.G. Finlay Guest

    I had a problem with mine (FV) lately too. Seemed to be the relay
    which I eventually bypassed (pump now works when the ignition is on,
    not just when the engine is turning over/running). Try bypassing the
    relay with a bit wire (can't remember which 2 of the 3 wires you
    connect - will check Haynes manual tonight and post it up).

    B.G. Finlay, Mar 6, 2006
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