overfuelin 405
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Thread: overfuelin 405

  1. #1
    Tadpole
    Join Date
    Dec 2004
    Location
    dorset uk
    Posts
    7

    Default overfuelin 405

    i have a 405 its overfuelin like buggery! ive changed the coolent temp sensor, the fuel pressure reg the co adjuster the plugs cleaned the airfilter fushed the coolent and oil and its still just the same! the management is a non airflow meter type which i belive use's a mapsensor in the ecu. i am pulling my hair out now! any ideas?

    thanks

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  2. #2
    Fellow Frogger!
    Join Date
    Feb 2002
    Location
    Tamworth NSW
    Posts
    496

    Icon7

    Hi there,

    I assume the "overfuelling" is evident through rich exhaust emissions (black smoke), high fuel consumption, loss of power etc. Can you confirm?

    I am not totally familiar with the 405 fuel management system. However, ECU management using a MAP (Manifold Absolute Pressure) sensor simply relates the air induction pressure to the throttle plate position. Thus, low pressure (high vacuum) should equate to a nearly closed throttle plate, therefore low fuel supply to the injectors. With high pressure (MAP) approaching ambient pressure, the opposite applies.

    Perhaps this relationship between MAP and throttle plate position is 'out of whack'? An air leak due to a split vacuum or breather hose (or one that is disconnected) will also put the ECU management into error.

    Hope this helps a little. Let us know what you find. Do you have a workshop manual (Haynes etc) that includes a trouble shooting chart?

    Cheers,
    Kim.

  3. #3
    Tadpole
    Join Date
    Dec 2004
    Location
    dorset uk
    Posts
    7

    Default

    Quote Originally Posted by KIMDEB
    Hi there,

    I assume the "overfuelling" is evident through rich exhaust emissions (black smoke), high fuel consumption, loss of power etc. Can you confirm?

    I am not totally familiar with the 405 fuel management system. However, ECU management using a MAP (Manifold Absolute Pressure) sensor simply relates the air induction pressure to the throttle plate position. Thus, low pressure (high vacuum) should equate to a nearly closed throttle plate, therefore low fuel supply to the injectors. With high pressure (MAP) approaching ambient pressure, the opposite applies.

    Perhaps this relationship between MAP and throttle plate position is 'out of whack'? An air leak due to a split vacuum or breather hose (or one that is disconnected) will also put the ECU management into error.

    Hope this helps a little. Let us know what you find. Do you have a workshop manual (Haynes etc) that includes a trouble shooting chart?

    Cheers,
    Kim.
    yeah black smoke about 7 miles to an imp gallon and the gas analiser says the emmissions are about 11-12% with the workshop manual quotin 1.5 % around right for this engine! im going to have a play about with the throttle plates whats the correct way to set these up? thanks

  4. #4
    Fellow Frogger!
    Join Date
    Feb 2002
    Location
    Tamworth NSW
    Posts
    496

    Icon7

    I would hesitate to advise re the throttle plate / MAP sensor checking process, mainly because I do not have access to the information. Also, it is only a suggestion at this point.

    Can you advise what model 405 you have, engine type etc. This may prompt some additional inputs from other 405 members on this site.

    Often, if the symptoms appeared quite suddenly, then the diagnosis may be traced to a faulty component, loss of signal to an ECU etc. Assume no restriction to primary air flow, filter blockage etc?

    Cheers,
    Kim.

  5. #5
    Member
    Join Date
    Dec 2004
    Location
    England
    Posts
    33

    Default

    Check there are no splits in the vacuum feed to the Map sensor, otherwise instead of reading vacuum, it could read a higher atmospheric figure and overfuel. Likewise, the map sensor could be stuck...To see if its stuck, pull the pipe off the map sensor and see what happens. If it isnt stuck it will stall, if it is, nothing will change.

    There are loads of things it could be, but you wont work out with out the use of a diagnostic pod, to tell you the values of each sensor. Youve change the coolant sensor (make sure its the right one if there is more than one, some cars have one for the gauge and one for the ecu), but also the wiring to the sensor could have a short, doubling up the resistance and giving a false value.

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