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Thread: Gas tank wiring

  1. #1
    Join Date
    Aug 2009
    Location
    Spain
    Posts
    322

    Default Gas tank wiring

    Hello!!!

    I have a question on the 851 gas tank wiring. According to the electrical schema, the four pole connector receives:
    1: (+) from injection relay.
    2: Earth
    3: Low fuel warning light
    4: (+) from ignition key

    But as I'm combining it with an ST4S engine + Monster S4R wiring loom (same engine, so fully compatible) I have this from the S4R connector:
    1: Earth
    2: Earth (from 1)
    3: (+) from injection relay
    4: Low fuel warning light

    It is quite obvious for me what to do with earth and warning light but it is not so obvious why the 851 pump assembly receive 2 positive input from both ignition key and injection relay.
    On my bike I have replaced the OEM connector in the 851 for a sealed four pole one as equipped by the S4R wiring loom and I've connected toghether both positive wires from the tank so that I have now 3 of the 4 ways in the connector connected:

    851 Tank
    1: (+) from injection relay AND (+) from ignition key
    2: Earth
    3: Low fuel warning light
    4: Free

    S4R Wiring loom
    1: (+) from ijection relay
    2: Earth
    3: Low fuel warning light
    4: Free

  2. #2
    Join Date
    Aug 2008
    Location
    Hastings, NZ
    Posts
    274

    Default

    Check out this thread for some detail, there are also wiring diagrammes in the technical section

    http://www.ducati851and888.com/showt...ng-Help-Wanted

    Cheers
    Nigel (& Claire)

  3. #3
    Join Date
    Aug 2009
    Location
    Spain
    Posts
    322

    Default

    Thank you for your answer but...

    I think you have swaped terminal 1 and 2, as 1 is + which comes from a relay energized straight from the attery and 2 is clearly marked as earth on the wiring diagram. Apart from that, if the fuel sender really acts like a switch (easy to check) then my connector should work fine. I'll try...

    Side note: on my post, terminal number were random, so not straight comparison can be done. Yours is fine.

  4. #4
    Join Date
    Aug 2008
    Location
    Hastings, NZ
    Posts
    274

    Default

    Fuel level switch terminals can be reversed (+ve/-ve) without issue as it is only a digital switch input. The fuel pump terminals have to be wired correctly for +ve/-ve otherwise the pump will run backwards; if the pump is wired incorrectly it sounds ok when you switch on the ignition but is not pressurising the fuel system.

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