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Intermittent Starting Problems - HELP! 850 1995

Our '95 850 Turbo is intermittently not starting. It turns over fine, just won't start some times. It SEEMS to be after the car has sat for a few minutes, but not long enough to cool all the way down. Although now it's starting to just do it all the time and the length of time may be totally irrelevant.. I pulled a 314 code from the A2 socket ("Camshaft position (CMP) signal missing or faulty"). A6 (ignition) didn't have anything in it. So I look for spark. No spark. The spark plugs are relatively new also (less than a year, and looked fine).
For some reason I try replacing the coil - no difference. Then I notice some disintegrating vacuum hoses near the CMP sensor - I replace those too. Still no difference. So I move onto the CMP sensor and test the lead as per the Chilton Manual's instructions. The first lead I test seems bad: It's supposed to have 12v to ground, and has almost none. Battery's connected and ignition on. It's the Brown wire with a black stripe. The second lead is fine, and the third I'm not sure about... I think it's just my multi-meter needs a new battery.

Anyway! Chilton just says "repair the circuit". What does that mean? Try and find a break in that brown/black wire? That seem really difficult! Where is the ECU? The wiring diagram shows the brown/blk wire supplying power to a number of sensors and being fed from the ECU. Perhaps I should start on that end?

Any advice would be hugely appreciated!

It's really hard to follow that wire. It goes into these closed up plastic case/sleeve things and disappears. I can't really imagine something happening to that wire... but I guess anything is possible.

Also - dose it seem like the symptoms fit with getting poor power to the CMP sensor?

Please help. I HATE electrical problems. But I think I hate taking my car to a mechanic a little bit more. ;)

Thanks again!!!
Jamie.








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    Intermittent Starting Problems - HELP! 850 1994

    Could it be a bad ground connection to the engine?








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      Intermittent Starting Problems - HELP! 850 1994

      Well, the CMP sensor does not use a common ground to the engine it just goes from the ECU to the sensor and back, so I don't think that is the problem - but perhaps I'm missing something - what were you thinking?

      Jamie.








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    Intermittent Starting Problems - HELP! 850 1995

    Looks like your camm rotation sensor is going bad. Replace it soon or you'll be stranded. It's only used when starting. Easy to reach and not too difficult a job but be careful with the seal. Some folks have had oil leaks afterwards. Part is around $50-60.








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      Intermittent Starting Problems - HELP! 850 1995

      Is what you're calling the camm rotation sensor, what Chilton/Volvo calls the camshaft position sensor? I've taken that off - it has something in it called a Hall effect switch - is this what should be replaced? Or do I have to go deeper into that opening and replace something else? I'm wondering, because you mention oil leaks, and I didn't break any oil seals to get the cam position sensor/hall effect switch off.

      Thanks a million!
      Jamie.








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        Intermittent Starting Problems - HELP! 850 1995

        I think the camm rotation sensor and camshaft position sensor mentioned earlier are the same thing. It's job is to let the engine know on startup what the cam shaft position is so it know when to send spark. Pretty common part to fail. It is on the side top of the driver's side of the engine. Here is link to picture of the part from fcpgroton website: http://www.fcpgroton.com/images/9146108.jpg
        (From the outside it basically just looks like a dust cover.) As far as I know you have to replace the entire unit, you would just be able to repair/replace the Hall effect switch inside.

        fcpgroton price new is $135 I got a used one for about $40. Biggest problem for me was getting to wire connector - I removed dist. cap to get better access.

        Good luck and hope it is your fix!








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          Intermittent Starting Problems - HELP! 850 1995

          That was it! You nailed it exactly. Even down to the $40 at the salvage yard! I'm back in business. FWIW the old one appeared fine - no visual indication of the failure. I was able to get the that electrical connection without taking off the distributor, but not without a few battle scars. And believe me I was not happy when I found out I had to remove that connector on the salvage car either! It was bad enough when my hands were in good shape to start... but when they are already all cut up and bruised it's even more fun! ;)

          Thanks to all!
          Jamie.







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