Illusive fault, 940 will not start!

Discussion in 'Volvo 940' started by Dave, Jul 22, 2005.

  1. Dave

    Dave Guest

    Hi, all.
    I have a '91 940se turbo estate with 178k on her, which over the last 8
    years has been an absolutely wonderful car. Doesn't owe me a penny, the only
    real expense being a replacement head 18 months ago. About 6 months ago it
    started cutting out while driving, for no obvious reason. Then 3 months ago
    it would not start.
    I also have a very low mileage (48k) '95 940 wentworth turbo estate, and as
    most of the engine components are the same decided to transpose those from
    the '91 to the '95 in a process of elimination. So far I have tried ignition
    amp, ecu, petrol pumps, crank sensor, all function perfectly in the '95.
    I have tried checking relays but they don't appear to be the same, so gave
    up on them.
    The only source of info available is the usual haynes manual which of course
    is absolutely less than useless. The ODB on the '91 doesn't work iether.
    Although I suspect an electrical fault, the car previously had been driving
    perfectly, I have always been religious in maintaining it mechanicaly even
    if cosmeticaly it is not brilliant. I am not sure where else to look, or
    whether it's even worth bothering. Maybe I should scrap it!
    I was hopeing someone on here may have had the same problem and found an
    answer, or might give me a guide as to analising the fault and thereby a
    solution.
    Any input at this juncture would be extremely appreciated. I have decided on
    a finite time limit, my wife is moaning, in which to sought the issue or
    scrap it. The old girl has 1 months extension (that's the car, not the wife
    of course).
    Thanks, Dave.
     
    Dave, Jul 22, 2005
    #1
  2. Try the Fuel Pump relay, the Interference Suppression relay (if fitted), The
    Ignition Control Unit and the Fuel Pressure regulator. Check all wiring and
    connectors (including earths), Distributor cap, Rotor arm and ignition leads
    and Coil. Other possibilities are the MAF sensor, Idle Air Control Valve,
    throttle switch and linkage. Once you have found the fault return all good
    parts to their original location and replace the faulty part(s). Also check
    on the Brickboard FAQ lists on VOC website.

    All the best, Peter.

    700/900/90 Register Keeper,
    Volvo Owners Club (UK).
     
    Peter K L Milnes, Jul 23, 2005
    #2
  3. Dave

    Tim C Guest

    I had a similar problem with my 940GL (and apparently the prior
    owner did too ;). It would drive _perfectly_, then stall occasionally
    in a hard, fast turn - and it wasn't the fuel pump.

    Turned out the wiring to the battery terminals had corroded
    completely away! Of course, it took me about 3 months of changing
    batteries, components, etc. ... The clue _should_ have been that
    every time the car jolted (i.e. big bump, sharp turn, etc.) the
    car would cut out, then mysteriously start again after a short time.

    My read is that what was left of the wire would shift, hence the
    battery would disconnect and the car would think something
    catastrophic had happened; eventually, the wire would slip back into
    place enough to let me start the car. Once this happened enough there
    wasn't enough current flowing through the broken wire to the starter,
    though the interior lights would usually run for a bit - and the dinger
    would start loud / high and run softer / lower if I left the door
    open (think capacitor discharge).

    The shielding on the wires was intact, so even when changing the battery
    it felt like it was still okay; eventually I wound up pulling the
    shielding back for some reason and the wire just disintegrated into
    a green dust...

    Anyway, I peeled it back another 6 inches or so (where it was nice
    and bright) and put on a pair of screw-down terminals from AutoZone.
    Not a single problem from the battery since!

    Best of luck, hope it's something as simple for you. ;)

    -TC
     
    Tim C, Jul 23, 2005
    #3
  4. Dave

    Randy G. Guest

    Poswer comes form fuel, compression, and a spark at the plug at the
    correct time. Pull a plug and see if it is moist from fuel. CAREFULLY
    remove a plug and ground it, and connect a plug wire to it. See if it
    sparks whyen cranking (Be SURE it is grounded to protect the
    electronic ignition). if you have those two things, then it is
    probably timing.



    __ __
    Randy & \ \/ /alerie's
    \__/olvo
    '93 960 Estate
     
    Randy G., Jul 23, 2005
    #4
  5. Dave

    Dave Guest

    Thank you all for your input so far. Perhaps I should have been a little
    more irrudite in my explanation.
    When the car wouldn't start my son called the RAC. They diagnosed it to be
    the distributor cap and replaced it. This did not solve the problem. Upon
    further examination they concluded it to be the fuel pump but were unable to
    take that any futher. This was the main reason fo me trying both fuel pumps
    first. Metering the fuel pumps while turning the engine over showed there to
    be both pulses and supply, as expected. Checking for spark, as Randy quite
    correctly commented on, proved to be good.
    From what I can see, correct me if I'm wrong, there are so many faisafe
    elements in both fuel and ignition systems on the 940 as with most modern
    cars, the main common denominator is the ECU (ICU), which I checked and
    proved to be ok. As I said earlier I tried what I felt were other common
    elements in the circuit, ie ignition amp (power amp); crank sensor (hall
    detector). So, the main elements for 'power' are there and they're
    controlers function correctly!
    This to me would seem to rule out both fuel relay and wiring, or am I wrong?
    Although I did try a spare fuel relay.
    So, as Randy again correctly said, perhaps it is timing. In which case how
    do I adjust the timing? Would poorly adjusted timing be the cause of
    intermittent cutting out while driving? The engine turns over ok with
    apparent compression, although not measured, and basic elements appear to be
    ok.
    I have only rudimentary knowledge of motor mechanics, I am in fact an
    electroncs systems engineer with specialisation in communications research.
    Perhaps my analyses of this system is flawed?
    I did consider removing the relay board to check for dry joints. I do know
    this has been commented on in the past within the newsgroup. However,
    initial inspection would seem to imply a rather complicated dismantling
    procedure, and I opted for trying other alternatives first.
    Thanks again to you all, Dave.
     
    Dave, Jul 23, 2005
    #5
  6. Well, the old standby for determining whether it is a fuel problem is a
    spray of starter fluid in the air cleaner box. If the engine goes vroom, the
    ignition and such are okay and you can focus on the fuel delivery.

    Another clue is the cutting out earlier - assuming it is related. If the
    dropouts were sudden (like turning off the key) it points to ignition, while
    if they were sags and recoveries (like taking your foot off the gas for a
    moment) the fuel is more likely. In addition, the tach is a good indication
    of ignition activity. Even while cranking you should see it kick a few times
    a second.

    Finally, I will assume the timing belt is okay because it should have been
    replaced during the head repair, so the cranking sounds normal.

    Mike
    (Communications field engineer for an electric utility)
     
    Michael Pardee, Jul 23, 2005
    #6
  7. Dave

    Dave Guest

    Thanks Mike,
    I'm probably being a little obtuse here though. What is starter fluid?
    Anything like lighter fluid, and would I put it in the air filter box or
    after the Air Mass Regulator?
    Volvo did the head replacement. Although expensive I have found from
    experience they do the job well, Whereas local garages do miss things. The
    head was a replacement and I asked them to replace anything they felt should
    considering the milage, seals, crank breather, etc.
    The engine cutting was akin to turning off the ignition. I couldn't tye it
    down to temp, speed, incline or any other variable. Plus, it only happened
    rarely.
    Thanks for the pointers I'll look at those points tomorrow.
    Dave.
     
    Dave, Jul 23, 2005
    #7
  8. Dave

    Randy G. Guest

    I was typing the same response when I saw your post. Good idea!
    ....or an intermittant ignition problem like a corroded connnection of
    a biodgradable wiring harness.

    __ __
    Randy & \ \/ /alerie's
    \__/olvos
    '90 240 Estate - '93 960 Estate
     
    Randy G., Jul 24, 2005
    #8
  9. Dave

    Randy G. Guest

    It is actually aerosol ether. use with care and caution if you wish to
    keep your eyebrows intact.

    __ __
    Randy & \ \/ /alerie's
    \__/olvos
    '90 240 Estate - '93 960 Estate
     
    Randy G., Jul 24, 2005
    #9
  10. Howdy folks


    Anything that can be sprayed and burns when lit wil do, e.g. perfum,
    WD40, etc. If you try it outside the airbox, you can even find out if
    the engine is sucking in air where it shouldn't.

    Or any other electrical connection. Overhere, we've had problems with
    martens, small weasel like animals, that like the smell (and obviously
    the taste) of warm rubber hoses and wire insulation. My Dad's car has
    had it's spark plug wires and an ABS wire nibbled in two. And a piece
    of French bread stuffed in between the intake manifold. My 945 untill
    now has had the hood insulation trashed and the engine cover pooped on.

    CU Mathy
     
    Mathy Van Nisselroy, Jul 30, 2005
    #10
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