Please help --which order of diagnosis for '87 740 Turbo No start !

Discussion in 'Volvo 740' started by circuit slave, Feb 25, 2006.

  1. Hi,

    I had a turbo boost problem --lack of power which I took care of. Now
    the car broke down on the freeway and it's really starting to

    I initially thougth it was the fuel relay and so I pulled it and
    resoldered to contacts and it was running fine---last time it would
    intermittent start was like 3 weeks ago. The car started up every
    time. I even bought new spark plugs.

    I thought it was the fuel pump because it was buzzing under the
    car--thinking it was the intank pump going out, but it's been fine. I
    was on the freeway yesterday and going 70mph and then the car
    deaccelerated and came to a stop.

    Now it just turns over and over but doesn't start. I checked the
    timing belt and it's fine.

    In what order would YOU go to try and solve? thanks
    circuit slave, Feb 25, 2006
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  2. circuit slave

    HankL Guest

    Get some starting fluid - if it runs, you have a fuel problem - if not the
    flywheel sensor needs to be replaced $35 at parts store - more at Volvo.
    HankL, Feb 25, 2006
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  3. circuit slave

    Boris Mohar Guest

    The fuel pump relay can fail in two major ways. One is due to open solder
    joints on the circuit board which you took care of. The other is contact
    erosion. Take out that relay again and clean the contacts, especially one
    closer to the middle with 600 abrasive paper. I fold a piece on it self and
    cut a small sliver from it. Using tweezers I insert this double sided
    abrasive in between the contacts and work them smooth.


    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things)

    void _-void-_ in the obvious place
    Boris Mohar, Feb 25, 2006
  4. circuit slave

    James Sweet Guest

    It's an '87, so it has no flywheel sensor. Instead it uses a hall sensor
    in the distributor. First thing to check is if it has a spark, that's
    easy enough. If the engine wiring harness is original then it will need
    to be rewired or replaced, if that's not the problem now it will leave
    you stranded later.
    James Sweet, Feb 25, 2006
  5. I FIXED IT !!!!!!! I am so happy. The wiring harness is old and
    crumbly. The car wouldn't start and so I started to fiddle with that
    block terminal--- there' s two (maybe you guys can explain).

    The one in the back that connects to the ignition coil-- it was tie
    wrapped under and I fiddled with it while I had someone start the car.
    It would start and then die. Start and then die. You had to give it
    gas on the pedal to keep it going. Well, anyway, with the ingnition in
    on position-- you could hear the injectors intermittently click.

    I carefully pulled both connection blocks (the large grey one and
    small grey one) out and individually wrapped each of them in tiny
    spiral wrap plastic.

    It starts ! yay!!!!! You don't know how glad I am----this has been
    going on for like 5 years I think !


    1. Is this part of the wiring harness when bought? I mean can this
    portion be bought separately?
    Instead of the rip off dealer price for the whole harness?

    2. Underneath the car I thought what I saw was a disconnected
    electrical plug--so I plugged it and the car started (I think this was
    just coincidence in moving the car creating the short) but I plugged it
    in and the over drive arrow light appeared on the dash and it wouldn't
    go out when pushing in the button. Is this somehow wrong?

    I mean is the arrow supposed to be lit or not? I mean before the light
    would stay off and then you push the button and it goes on. But then
    why is it disconnected under the car then?

    thanks guys for helping me figure it out---if I didn't find it by
    accident : )
    circuit slave, Feb 25, 2006
  6. aarrrrrrg!!!!!!!!! The car just broke down again : (

    I went to put in gas and then it died. I tried to start it--it started
    up and then I gave it gas and it died. It just turns over and over !
    circuit slave, Feb 25, 2006
  7. Kind of a shotgun approach, but given the prevalence of problems and the
    sort of symptoms you have: check and/or thoroughly clean up the connections
    at the positive post of the battery. Our 85 has a separate wire that
    attaches to the clamp bolt itself, and when that ring terminal gets funky
    the engine dies. There is also a 10 AWG red or brown or orange (never could
    tell which) wire that comes away from that clamp that likes to corrode in
    two. Drove me completely crazy when it happened to mine.

    BTW - a quick-and-dirty way of deciding whether to suspect ignition or fuel
    in these beasts is to watch for the tach kicking when cranking. No kick
    every second or so usually means no ignition.

    Michael Pardee, Feb 25, 2006
  8. circuit slave

    James Sweet Guest

    The wiring harness runs from the ECU in the passenger footwell and
    snakes all around the engine under the intake manifold, over around to
    the air mass meter and interconnects with the ignition harness. If you
    found crumbling wires, I assure you there are more, if you remove the
    harness and split it open, the large bundle of wires under the intake
    manifold will have the insulation crumbling which causes bare ignition
    wires to mingle with bare injection wires and the end result is either
    no spark, no fuel, or intermittent gremlins. Remove, then rebuild or
    replace this harness, the car will never be dependable with it in its
    current state and there's no way you can repair it sufficiently with it
    snaked around the motor.

    That sounds like the overdrive solenoid wire. The arrow should be lit
    only when the overdrive is disabled by pressing the button on the side
    of the shift knob. If the wire to the solenoid was disconnected then the
    overdrive would not engage regardless of whether the arrow was off or
    not, unless someone modified the solenoid to eliminate the sometimes
    troublesome and rarely used lockout feature.
    James Sweet, Feb 25, 2006
  9. circuit slave

    James Sweet Guest

    See my last post, your wiring harness is shot.
    James Sweet, Feb 25, 2006

  10. Mike, the tach does jump on turning on the ignition--I thought it was
    the ignition as well, but I jiggled it while starting and it starts the
    engine turning over and over.
    circuit slave, Feb 25, 2006
  11. Okay, so what you're saying, James, is the arrow on the dash is lit
    most of the time while driving, and then when you use the overdrive
    (press the little button) it should go out, but it is enabled ?
    circuit slave, Feb 25, 2006
  12. That's exactly what it looks like, James--by the manifold the fat
    bundle of wires by the idle control valve---they're crumbly and
    bare---I'll look at this. Thanks for all the help you've been
    providing : )
    circuit slave, Feb 25, 2006
  13. circuit slave

    James Sweet Guest

    No, the arrow should normally be off, if the arrow is on, then it means
    the overdrive is locked out, just like if you put the shifter to "2"
    instead of "D", 3rd gear will be locked out. The OD lockout (arrow on)
    can be useful if you're towing a trailer or going up some hills that
    cause the transmission to hunt, that is shift in and out of overdrive
    not able to decide which gear to stay in.
    James Sweet, Feb 26, 2006
  14. James, have you replaced the harness before? Is there a diagram
    somewhere, or should I just tag each connection before removing?

    circuit slave, Feb 26, 2006
  15. I just stretched my new one out on the ground before removing the old one,
    and used masking tape to identify the conectors. I started at the battery
    end, looking at the connector style, and matched each with the one on the
    existing harness. The fuel injector connectors are interchangable, so
    connect them where they reach best.

    After I labeled them, I disconnected the big connector near the battery
    (oh - the battery was already disconnected at this point!) and connected the
    new harness there. I worked my way down, disconnecting the old and
    connecting the new as I went. I had to cut off the old injector connectors,
    because the old harness was too stiff to fit through the manifold there.

    Look carefully where the wire connects to the starter. I put the wire on the
    wrong terminal and decided the starter went bad while working on the
    harness. D'oh! Also don't forget the oil sender wire, which also runs a long
    way around the engine. All told, including my starter error and working
    slowly, I spent most of a day doing the replacement. It could be done in an
    hour by a fast worker who wasn't so very cautious.

    Michael Pardee, Feb 26, 2006
  16. circuit slave

    James Sweet Guest

    When I rebuilt my harness I left it connected to the ECU and just
    unwound it from the engine, taking a few digital pics along the way. The
    oil pressure sender wire looked ok, it was below freezing and I was
    working outside in front of my house so I just cut the wire and put a
    connector on it rather than jack up the car, remove the belly pan and
    muck with disconnecting the wire. I cut out all the damaged wires one at
    a time and soldered in new ones between the connector and a good section
    of harness by the firewall. If I'd had one on hand I would have just
    replaced the whole harness though, or picked up a used one and rewired
    it inside the warm house but this did get me back on the road.
    James Sweet, Feb 26, 2006
  17. Thanks, Mike and James---it's the dumb crumbly harness---I just got it
    started again !

    I'm going by some spiral loom just to see if I can pinpoint where the
    faults are---I will order a updated OEM harness

    P.S. the oil light flickers now ? I'll check the oil--but I read
    other's with flickering oil light, what's it mean?
    circuit slave, Feb 26, 2006
  18. circuit slave

    James Sweet Guest

    Did you check and see if Dave Barton has any harnesses for that year
    car? He's the best deal I've seen as far as having what you need in
    stock and knowing it's the right part. You might get lucky on ebay or in
    a local wrecking yard but that's a gamble. If you're handy with a
    soldering iron you can pick up some wire and heatshrink tubing and
    rebuild an old harness, best to pick one up from a wrecker and rewire
    that so you don't forget how everything goes together.

    The oil light flickering could be low oil pressure, a bad sender, or
    simply crumbling wiring, it's in the same harness.
    James Sweet, Feb 26, 2006
  19. That is disturbing - it is probably a sender or wiring problem, but you
    can't just ignore it. If the sender has a drop of oil on the terminal where
    it has been leaking you can be sure the sender needs to be replaced. If the
    light still flickers with the sender disconnected you know you have a wiring
    problem with it.

    If the sender needs to be replaced you can do that easily enough. If the
    problem is in the harness you can live with it until you get a new harness
    in, but then how will you know if you really have oil pressure problems?

    Michael Pardee, Feb 26, 2006
  20. Right--actually since the harness was crumbling---I temporarily sprial
    wrapped it --and I think it's fine.

    Mike, and James, I have a question. I think my turbo might blow up. I
    started a thread here:

    and I cleaned out the oil trap and now the engine has sucking at the
    oil cap like it should and no more fumes and smell and smoke in the
    engine area like before---

    But I think the pressure is now blowing the hose out of the "Y' elbow
    nipple from pressure ?

    It didn't do this before when it was clogged. How can I test the
    actuator or make sure it's opening. Doesn't it open after boost?
    maybe that's why whomever shaved a hole in the compressor side of the
    circuit slave, Feb 26, 2006
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