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900ss Level Sensor Problem(?)

Discussion in 'Supersport (1974-2007)' started by petown, May 21, 2019.

  1. Well, I'm finishing up the winter/spring project of refurbishing a 1995 900SS-SP which had been parked for over 15 years with a tank-full of fuel - what a mess. I replaced the fuel pump with the recommended Airtex E2008, new filters, fuel lines, etc. The original metal level sensor seemed to clean up after spending a week in white vinegar but it did not initiate the low fuel light with an empty tank.
    I really don't care whether the warning light actuates or not; however, I'm confused as to how the fuel pump is supposed to normally operate, or not, when the ignition is turned to "on", without the engine being started. I seem to remember from a CR I owned years ago that the fuel pump would run for a few seconds after the ignition was switched on, then turn off. When I switch on the SP's ignition the pump runs continuously until the ignition is switched off, whether the tank is full of fuel or empty.
    I pulled the sensor from the tank, disconnected the pump leads, and disconnected the harness connector. I have continuity from the sensor connector's #4 pin to the (+) lead to the pump, and #3 to the (-) lead (BTW Haynes call #4 position "A" and #3 is B); no continuity anywhere else on the sensor. Haynes shows the connector's #2 lead going to the turn signal relay and #1 to the starter switch. I've replaced the relay.
    Could anyone confirm how the fuel pump is supposed to operate/shutoff with the ignition switched on and the engine not running? I did come across a comment on another forum that stated the pump should run continuously - I'm just looking for another opinion.
    If the pump should shut off after an interval what would be your thoughts as to why mine continues to run? I really don't want to pay the obscene price Ducati wants for the latest version.
    Thank you in advance.
    Ed
     
  2. Ed, when you turn the ignition on, the first thing youll hear is the fuel pump run. It basically runs all the time and will only go off when you switch the ignition off. I know this as I have had the fuel tank dry during builds and it has gone on. Hope this helps. Ian
     
  3. Just to add, its a low pressure pump, and excess fuel is directed back into the tank.
     
  4. Thanks for the response, that's very helpful. Just seems like you wouldn't want to be able to run it dry for any length of time.
    Next step, put fuel back into it and we'll see if this thing runs after the long hibernation.
    Thanks, again.
     
    • Like Like x 1
  5. You have probably already discovered this, but the other thing you will need to do is clean the carb bowls, float needles and jets. I have found that if I do not use the bike during the winter the float needles gum up and stay open. Then the pump fills the cylinders with fuel. The solution is to drain the carbs if the bike is to be left for more than a couple of months.
     
  6. I use petrol additive if the bike is standing for any period of time.......the best one I found was branded Mountfield for lawn mowers, but also Screwfix do one called No Nonsense which is cheaper.

    My mower carb was well bunged up in the tiny ports and Wynns carb cleaner only partly dealt with it, which surprised me as it is normally damn good.

    Running the Mountfield additive in half a mower tankful of fuel sorted it out completely in two hours.
     

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