Strange CAS Behaviour

Discussion in 'Z32 Technical' started by antman, Apr 18, 2017.

  1. antman

    antman Member

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    Hi guys, I got a CAS related issue when cranking with fully charged battery...no spark at all.
    I removed the CAS and turned the CAS shaft by hand and spark and injectors work. Fuel pressure also primes.
    Checked loom for breaks/intermittent faults and also checked all earths are ok...fitted new CAS loom connector and tried 2 other known working CAS units..same issue.
    I also checked cam turns when cranking...took the plastic cover off the CAS to see it turns while cranking.
    Why does CAS not work when on the motor???

    What am I doing wrong?
     
  2. WazTTed

    WazTTed Grease Monkey

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    have you checked the Cas pin on the end of the cam isnt damaged?
     
  3. antman

    antman Member

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    Yes I have checked that as well. Also checked that the cas turns when cranking.
    Pretty stumped here.
     
  4. Chrispy

    Chrispy Pretentious Upstart

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    Tried a different PTU?

    Any error codes?

    I'm clutching a straws though.
     
  5. Fists

    Fists Active Member

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    Install the CAS, clear ECU codes then try crank it, then check codes again and see if it throws a CAS code. If no codes and you have the ability to try a hill start without getting your car stuck down the street then that could be a useful test, the ECU may not be getting the 'cranking engine' signal for the starting injection pulses (different to normal running injector pulses).

    Also probably check battery voltage, ECU could be starving for power while cranking.
     
  6. ProckyZ89

    ProckyZ89 Senior Member

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    How are you checking for spark?
    So you have spark when the CAS is removed and your turning by hand?..
     
  7. antman

    antman Member

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    Have another coil pack with plug earthed on top plenum.Yes correct, sparks by turning by hand.
     
  8. antman

    antman Member

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    A tow start is a good check....no hills in my ares.. Thanks
     
  9. Martin Williams

    Martin Williams Active Member

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    What voltage have you got across battery terminals when you are cranking engine? What is the CCA or cold cranking amps of your battery?
     
  10. antman

    antman Member

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    Thanks for all the advice. Good news is it is sorted.
    This is a first for me...the PS pump pulley had jammed due to the fact that the bolt that it pivots on was not tightened and prevented the pulley from turning. So when cranking there was enough friction on the PS belt to slip without squealing but enough drag to really labour the starter. What I assume the problem to be was that the starter was drawing so much current the ecu was being starved of power. After I sorted the jammed PS pulley the motor started. Funny thing is the motor still cranked at the same speed with and without belt drag. There may still be an issue of poor earth or power feeds that maybe need sorting.
    Thanks again for the advice.
     
  11. tassuperkart

    tassuperkart Its a lie I tell you!

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    The CAS is powered from ignition via the ECCS relay and a fuseable link on the drivers side near the firewall.

    Id say what you have is a "lazy" relay that is releasing when the starter is engaged and not pulling in.
    Or the fuses are corroded and showing high resistance.

    A simple testlight on the CAS +ive power wire (B/W) and ground B() will confirm this when cranking under load, as you had or try with all the headlights and accessories on flat out to give the battery a bit of a hiding.

    E
     

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