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Mystery electrical glitch 700 1989

Hello All,
This is something I'd give an eyetooth to solve. My '89 740 GL sedan does this, and why I don't trust it on the road. Several times in the past, while out driving, it will quit running, inexplicably and without warning. Then it will not restart ... until it completely cools down. Most often, overnight. After sitting overnight, it will start right up again. I've had to be towed home on two occasions. I left it with my mechanic, once for three days, and he could not recreate it.

My best, and only guess, is that it's a failing electrical part that is responding to heat. When it reaches a certain temperature, perhaps, it shuts off, then is able to work again at some point. Please, anyone, who has had this problem, tell me how you solved it. I'm willing to throw a part or two at it if I can make it reliable again. Thank you!
Jim








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    Mystery electrical glitch 700 1989

    More diagnosis.
    When it dies does it crank over or just dead?
    If it cranks over have you checked for spark?
    Does the tach move when cranking?
    You get the idea.
    https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm
    --
    Post Back. That's whats makes this forum work.








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      Mystery electrical glitch 700 1989

      Thanks aleekat,
      Yes, it turns over. I'll have to check for spark and tach movement when the crappy weather evens out in TN over the next couple of days. I will get back.
      Jim








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        Mystery electrical glitch 700 1989

        In the mean time check and see if the OBD has any fault codes stored. (I "think" 1989 has an OBD system but I can't remember for sure.)
        --
        Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)








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          Mystery electrical glitch 700 1989

          Yes, Chris, it does have that feature. I may have to rely solely on the fault info due to the fact that recreating this glitch is so difficult. Like I said, my mechanic gave up after trying for 3 days to duplicate the problem. I will get back with my findings. Thanks!








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            Mystery electrical glitch 700 1989

            We had a 1990 740 Regina but my mother-in-law had a 1989 740 (Bosch with regular coil on the firewall). Her coil, well her CAR'S coil, started to go bad and it was intermittent like that - started and ran OK, then as it heated up it started to crap out. Might be worth swapping in a known good one just for kicks.
            --
            Current rides: 2018 Volvo S60 Inscription (What the heck do all these buttons do?), 2005 Volvo S80 2.5T (Soon to go bye-bye), 2003 Volvo V70 2.4NA (The family "truck"), 1973 Volvo 1800ES (STILL not road worthy!)








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              Mystery electrical glitch 700 1989

              This has been suggested to me, Chris. I'm going to try a different coil and see if it could be that simple. Thanks, and i will report back.








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          OBD & 700-900 Fuse & Relay Box 700 1989

          Hi Chris and Jim,

          Unless Turbo, 1989 normally aspirated 700 is like 1989+ 240 is OBD-1 equipped. See the FAQ article on OBD, or review your Volvo 'green' manual service doc, or your Haynes manual. (Clymer published also, I guess, yet a long time ago and out of print.)

          A CHECK ENGINE light on the instrument cluster?

          Siemens / Bendix Regina fuel injection / Rex ignition started with some normally aspired (not Turbo) in 1990? I guess 1990. Square ignition coil is Rex. Round coil is Bosch.

          To check OBD:
          https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

          Ignore Motronic info - specifically in the table columns where the header row states Motronic.

          Yet there is the other issue that affects all 700-900 series is the fuse and relay platform that is, as you know, hidden behind the ashtray. The fuses in front and the relay in back.

          Heat related issues that afflict electrical components and connection can persist in Winter, though usually Summer will reveal these or Summer heat will also exacerbate heat related issue.

          In all 700-900 Series, the fuse and relay is a serviceable item as the wire harness terminates at the under side the fuse / relay platform in terminal connectors that insert and secure to the platform. The fuse and relay terminals slide into the wire harness terminal. Corrosion forms and can cause heat. High current loads on the platform like the white fuel injection relay can actually begin to melt under and around it. Correspondingly, intermittent faults can form.

          The white fuel injection relay can form internal faults at the solder welds inside. The welds may have cracks, yet make a contact, and as the relay heats up, the cranks may open, and the engine stalls. Always good to keep known good spares in the trunk and on the shelf.

          Both fuel pumps run when the dash light are on yet do not start the engine?

          You've checked for spark and verified fuel delivery?

          If not Turbo, you do service and replace the preheater flap valve thermostat on the upstream side of the air filter in the air filter box. These always fail to HOT all the time, closing the ambient air intake, so it is max heat from the heat shield around the exhaust manifold carried by an accordion style tube to the non-Turbo 700-900 box underside ruins an AMM. Though an OBD check for fault codes at socket 2 (fuel) and 6 (ignition) may reveal a fault code or not. Bosch is forgiving up to the point engine control can't compensate or the intermittent fault may not be so intermittent, so codes or set. You may need to test engine control components and wire harness connection using a digital electric multimeter.

          You do have a crank position sensor (CPS) and these also fail intermittently at first. CPS failure is a no-start condition. An indicator of CPS failure is the outer sheath peeling away after decades or, if after market, years of under-hood conditions.

          Meanwhile, back at the fuse and relay platform, and peeling apart the 700 and newer series' interiors sucks, remove the ashtray and use a light to visually inspect the relay platform. See any of the housing plastic warped from heat? Give the fuses and relays a wiggle? Some Deoxit-D spray at these and other wire line connectors all along the watchtower wire harness helps.

          See here:
          https://www.brickboard.com/FAQ/700-900/ElectricalCircuitsRelays.htm

          See the comments by John Sergeant and others on this page.

          Else, begin your diagnosis for cause to seek a repair resolution.

          See stalling and starting problems.
          https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

          Spook and other 700-900 series sages can provide you additional help. I've not ever owned a 700 and newer series Volvo.

          Almost got a non turbo 1992 740 in white with M47 transmission. Wah. In a good shape, and now gone, a year ago or so.

          Questions?

          Hope that helps you.

          Unemployed Yet Again MacDuffy's Buttermilk & Ultra Sour Dough Bread Tavern.
          --
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            OBD & 700-900 Fuse & Relay Box 700 1989

            Thanks a bunch for so much detailed info, kittysgrayvolvo! I'll begin further digging and get back pending my weird schedule and TN weather conditions. Jim








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      Mystery electrical glitch 700 1989

      Thanks aleekat,
      Yes, it turns over. I'll have to check for spark and tach movement when the crappy weather evens out in TN over the next couple of days. I will get back.
      Jim







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