1997 Volvo S90 crank but no start

Discussion in 'General Motoring' started by ojm8183, Jan 11, 2006.

  1. ojm8183

    ojm8183 Guest

    1997 Volvo S 90 cranks but doesn't start. I have replaced the RPM sensor, I
    have tried replacing the engine computer with a known good one but it still
    would not start. I have no spark and no injector pulse. The car will start
    after many long cranking tries. The car has about 75,000 miles. I am an
    ASE master mechanic with many years experience and this once has me
    stumped. Any suggestions what might be the problem. Could it be the
    coolant sensor even though the one in there test fine? I have tried
    replacing the coolant sensor and am still having the same problem, any
    ideas, thoughts, spells that will make this car run???/
    ojm8183, Jan 11, 2006
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  2. ojm8183

    James Sweet Guest

    If there's no spark then you have an electrical problem somewhere. I'm
    not real familiar with this car, are there any relays that control power
    to the ignition control box or ECU?
    James Sweet, Jan 11, 2006
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  3. To be quite honest, you are not a very good master mechanic if you cannot
    solve a basic ECU power / primary igntion problem.

    Check and replace the main relay, and check the ECU is powered up and has
    good ground on the relevant pins.

    If that is ok, which RPM sensor did you replace? There are two. Flywheel and
    cam sensor. You need both working.

    A dud CTS or break in the wiring will not prevent the ecu from fueling- it
    will default to a fixed value. This is fundemental knowledge.

    Tim \(remove obvious\), Jan 11, 2006
  4. ojm8183

    ojm8183 Guest

    Tim, I did replace the main relay, that is basic. The ECU is powered up
    and has a good ground to the relevant pins. I replace the RPM sensor and
    the cam sensor tested fine, I replaced it just to be sure.

    What other suggestions would you have?!
    ojm8183, Jan 11, 2006
  5. ojm8183

    Tim.. Guest

    Right, so we can assume:

    a) The ECU is properly powered with +12v and 0v.
    b) There is a cranking voltage of at least 5v AC from both the CAS and the
    c) There is +12v present on the injector rail.

    Given that you say there is NO injector action OR primary switching this
    could rule out the dual igntion amps.

    Does the tacho needle jump at all during cranking? If not then its either
    possibly a dead ECU or a broken harness wire- the ECU is not aware the
    engine is turning.

    If the tacho is jumping then you must have injection takign place in which
    case re-examine the primary feed to the amps and coil packs.

    At this point i'd firstly use the jumper and set the ECU to manual actuator
    test mode and see if it is capable of firing the injectors and / or use a
    FCR to capture live data during cranking.

    Any past history of problems with the car, or did this happen suddenly out
    of the blue?

    Tim.., Jan 11, 2006
  6. ojm8183

    John Smith Guest

    Could the chip in the key be acting up , or the antenna in the steering
    column isn't working?
    John Smith, Feb 3, 2006
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