Ignition query...

Discussion in 'Technical' started by pennyarvs, Apr 12, 2013.

  1. pennyarvs

    pennyarvs New Member

    Been longing to post this question here. Just took me time to try a few things first.

    Wondering why the zed's having difficulty firing during hot days. Engine cranks but doesn't fire. Can hear the fuel pump priming healthily otherwise. Whenever I leave the car parked under the glaring sun after usually 4hours in between commencement of work and lunchbreak, doesn't wanna fire on the first try... but would never fail firing on the second try. And never happens when it's cold.

    Could this be related to a failing FPR, fuel damper or fuel filter?!


    AAA :zlove:
     
  2. WhiteNight

    WhiteNight Littering and...

    The fuel in the engine bay is too hot.

    A bit of vapour lock prevents it from starting. A few attempts moves the fuel aroud a bit.
     
  3. pennyarvs

    pennyarvs New Member

    So what would solve such issue?
     
  4. SuperZ

    SuperZ Resident Z lunatic

    White night is spot on.

    The heat may also be causing the fuel to expand and leak under pressure through the hose ends compounding the problem of a vapour lock building up (not much obviously) can you see any vapour coming out the fuel hose ends on a hot day? A Fuel pressure gauge is handy in this situation as you can see if it loses pressure suddenly or slowly so you can see if this is compounding the problem of the vapour lock.

    Are you missing the bonnet insulator??? This can make the problem worse obviously as it can heat the engine bay right up on a hot day.

    1. Consider insulating the fuel lines with insulation tape. (I have myself - lol)
    2. Check the hoses are tightly connected at the ends
    3. Make sure the fuel line doesn't rise up in the air at any one point so as to allow a vapour lock to build up i.e. unnecessarily looped into the air - this can happen if your running extra line from the filter to the motor.


    In the end your trying to reduce the possibility of air / gas building up at any one point in the fuel lines causing the vapour lock - the vapour lock will obviously be close to fuel rail on the inlet side

    Goodluck
     
    Last edited: Apr 13, 2013
  5. pennyarvs

    pennyarvs New Member

    Took the bonnet insulation out since I got the car in 2009 as it was all fugly and messy. Could be a contributing factor to it heating up quickly.

    Any of you guys got a photo of where to put the insulation tape on the fuel lines?!


    AAA :zlove:
     
  6. tassuperkart

    tassuperkart Its a lie I tell you!

    Youve got quite large injectors Arve. The engines ECU ignores all running maps when the key is flicked and looks up cranking tables. These particular fuel maps are only temperature dependant and are arrived at with stock injectors in mind. One the engine exceeds a threshold rpm, the ecu will look at its running maps along with afterstart enrichment corrections.
    Even with a tune, and a corresponding adjustment of the VE tables (IIRC "K" value) to compensate for the larger injectors, often the cranking tables are just too fat for a hot engine. I have noticed this in my humble atmo Zed. Vastly overfueled on crank and after start enrichment.
    However, a cold engine will tolerate excessive cranking fuel quite well.

    Id be pretty dubious of vapour locking as an issue. Just flick the key and 35+ psi of fuel pressure will deal with any pesky vapour pockets that otherwise might stop a carby car.

    The iac's in the Zed open fully when cranking to admit additional air. However, they are only a relatively small valve and if the engine is overfuelled from the cranking tables when hot then there is insufficient air to create a good start environment.

    Try this next time its hot. Open the throttle about 3 or 4mm and then crank the engine and immediately lift the throttle when the engine "catches" to prevent engine racing.

    If this solves the problem then my advice would be to just live with it rather than chasing funky ECU hot cranking adjustments. Hot cranking and AFSE are pretty fine.
    You might find if the throttle opening thing works, there will be a "sweet spot" of throttle opening which gives the best results.

    See how you go.

    E
     
  7. pennyarvs

    pennyarvs New Member

    Good info. Will try that next time. Thanks Evan...


    AAA :zlove:
     

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