940 se injectors not firing (LH 2.4)

Discussion in 'Volvo 940' started by Bilko, Aug 10, 2003.

  1. Bilko

    Bilko Guest

    Hi

    This car died on the motorway a couple of weeks ago and has been dead since.

    Some info...

    - The car won't start but cranks.

    - I am getting spark which will jump 1/4 inch when tested against the block
    so I assume the problem must be fuel delivery.

    - The fuel pump runs.

    - The FI relay activates.

    - The radio suppressor relay activates.

    - The wiring from the injectors to the ECU pin 18 (injector signal) pin is
    OK.

    - The supply and ground voltages at the relevant ECU pins are OK.

    - The other pin of the injectors is getting 12v via the radio suppressor
    relay.

    - I removed a spark plug and held a cotton bud in the cylinder as the engine
    was cranked -- there was no sign of fuel on it. Also, I used a long
    screwdriver as a stethoscope to listen at an injector... I couldn't detect
    any clicking.

    - When I crank the engine the voltage read across the pins of all injectors
    remains 0.0v so it looks like the pulse signal from the computer isn't
    working.


    All I can think of is a bad ECU... anything else I'm missing?

    Any advice would be welcome.


    Thanks

    Bilko
     
    Bilko, Aug 10, 2003
    #1
    1. Advertisements

  2. Bilko

    Peter Milnes Guest

    Yeah the series resistor pack for the injectors would seem to have become
    disconnected somewhere.

    Cheers, Peter.

    : Hi
    :
    : This car died on the motorway a couple of weeks ago and has been dead since.
    :
    : Some info...
    :
    : - The car won't start but cranks.
    :
    : - I am getting spark which will jump 1/4 inch when tested against the block
    : so I assume the problem must be fuel delivery.
    :
    : - The fuel pump runs.
    :
    : - The FI relay activates.
    :
    : - The radio suppressor relay activates.
    :
    : - The wiring from the injectors to the ECU pin 18 (injector signal) pin is
    : OK.
    :
    : - The supply and ground voltages at the relevant ECU pins are OK.
    :
    : - The other pin of the injectors is getting 12v via the radio suppressor
    : relay.
    :
    : - I removed a spark plug and held a cotton bud in the cylinder as the engine
    : was cranked -- there was no sign of fuel on it. Also, I used a long
    : screwdriver as a stethoscope to listen at an injector... I couldn't detect
    : any clicking.
    :
    : - When I crank the engine the voltage read across the pins of all injectors
    : remains 0.0v so it looks like the pulse signal from the computer isn't
    : working.
    :
    :
    : All I can think of is a bad ECU... anything else I'm missing?
    :
    : Any advice would be welcome.
    :
    :
    : Thanks
    :
    : Bilko
    :
    :
    :
    :
    :
     
    Peter Milnes, Aug 11, 2003
    #2
    1. Advertisements

  3. Bilko

    Bilko Guest

    --


    Thanks for the suggestion, but this 940 is a non-turbo and doesn't have a
    resistor in series with the injectors. The +ve feed for the injectors comes
    direct from the suppressor relay.


    Thanks

    Bilko
     
    Bilko, Aug 11, 2003
    #3
  4. Bilko

    Bilko Guest

    --

    I forgot to mention in my original post that I'm getting an engine speed
    signal to the FI ecu (pin1 ~6v when cranking) from the EZK ignition unit so
    I don't think it's the RPM sensor.


    Thanks for the input.

    Bilko
     
    Bilko, Aug 11, 2003
    #4
  5. Bilko

    Tim.. Guest

    since.

    Check the ballast resistor pack on the drivers side (i think) suspension
    turret.

    Tim..
     
    Tim.., Aug 11, 2003
    #5
  6. Bilko

    Tim.. Guest

    since.

    PS. You may not have a ballast reistor pack on this engine, some have, some
    haven;t- fingers b4 brain syndrome!

    With the igntion on, and fuel pump primed, try grounding the injectors to
    ecu line to earth for a secord or so, then crank. If the engine fires you
    know spark and fuel pressure is fine, and 12v to the injectors is ok.

    Then check very carefully all the ecu earth's.
     
    Tim.., Aug 11, 2003
    #6
  7. Bilko

    Bilko Guest

    No this car doesn't have ballast resistors -- it uses high impedance
    injectors.

    I'll try as you suggest and see how it goes.
     
    Bilko, Aug 11, 2003
    #7
  8. Bilko

    volvowrench Guest

    by Bilko dropped his wrench, scratched his head and
    mumbled,
    Since the auxiliary fan relay and the radio suppression relay have the
    same P/N you can swap them and see if there's a difference. If you ground
    the fan relay at the radiator switch through a test light, the fan will
    run with the key on--easy way to check both relays for operation.

    If that fails I'm afraid the control unit has left the building. That's
    the only thing left that generates an injector pulse.

    Bob
     
    volvowrench, Aug 13, 2003
    #8
  9. Bilko

    Bilko Guest

    Yes, looks like you may be right and the ECU itself is the problem.

    Tried everything else I could think of that would stop the injectors
    pulsing -- no RPM signal, bad wiring, faulty injectors, bad suppression
    relay, bad ECU supply or grounds, erroneous WOT signal from TPS putting the
    ECU in "clean start" (flooded engine) mode...

    Luckily it's not my car... it's the father-in-law's. I think he's out at
    the moment looking for a car with a carburettor.... :)


    Cheers

    Bilko
     
    Bilko, Aug 14, 2003
    #9
  10. Bilko

    Tim.. Guest

    Apols for not being online lately- blasted Lovsan virus bolloxing my pooter!

    Sounds like you have successfully eradicated any other fault with the car
    and it does point to an ECU failure.Makes a refreshing change that someone
    takes a logical approach to fault finding rather than just automatically
    blaming the ecu!!

    It would be worth having ATP check your ecu on their bench testers local to
    you. http://www.atpelectronics.co.uk just to be sure. This costs £35 which
    is discounted if your ecu is faulty and you order a reconned or new one from
    them.

    Tim..
     
    Tim.., Aug 19, 2003
    #10
  11. Bilko

    Bilko Guest

    Just to let you all know it was indeed the ECU that was at fault.

    A free replacement was procured from a scrap car, plugged it in and the
    beast came to life with the first turn of the key... :-D


    Cheers

    Bilko

    --
     
    Bilko, Aug 23, 2003
    #11
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.