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LH2.2 Hall Sensor Wiring Issue 700 1985

posted by  brickborg on  Mon May 18 14:52 CST 2020
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Car is a 1985 760 Turbo, LH2.2,

Just recently finished converting to a block mount distributor, and now have no spark. I was poking around with a multimeter today, and it looks like the Hall Sensor wiring may be damaged now. I performed the test outlined in the 700/900 FAQ:

"Undo the distributor connector. When the ignition is ON the Voltage between positive terminal (red lead -Nr. 3) and ground should be approx. 11V. Voltage between (blue lead - Nr.2; middle one) and ground should be 5V although if you put it on a scope you would see the sharp rise and fall from 12v to ground as the distributor rotates. Pulse frequency varies as rpm is increased. Resistance between (black lead - Nr. 1) and ground should be close to zero Ohms."

That last sentence is my issue- when I test that terminal to ground, I get 29.8 ohms. I assume this means there's a broken/corroded wire somewhere? An issue with the EZK? Is this close enough to zero that this isn't part of my issue?

Any pointers would be much appreciated.








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    LH2.2 Hall Sensor Wiring Issue 700 1985

    posted by  aleekat on  Tue May 19 09:19 CST 2020
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    last visit: Fri Oct 24 13:19 CST 2014
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    Usually close to zero is .2 to .5. 29.8 too much.
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      LH2.2 Hall Sensor Wiring Issue 700 1985

      posted by  brickborg on  Tue May 19 09:25 CST 2020
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      So I did another test last night, and I noticed that the resistance from that terminal to ground is 0.3 ohms with the ignition off, and I get the much higher number when the ignition is on.

      Would that indicate an issue with the wiring or grounding inside the EZK?








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        LH2.2 Hall Sensor Wiring Issue 700 1985

        posted by  aleekat on  Tue May 19 10:19 CST 2020
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        last visit: Fri Oct 24 13:19 CST 2014
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        The EZK computer is pretty robust. I don't ever recall reading about a bad one in your year group on this board for 20yrs. I have an 85, but it's been yrs since I was forced to do a full hall sensor test for a no start. I'm not sure if the zero ohm reading is only with the key off? Maybe someone else may know.
        Here's a link. You need Flash to view the manuals: (not downloadable)
        http://www.volvotips.com/index.php/740-760-780/volvo-740-760-780-service-and-repair-manual/

        Scroll down to these files:
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          Couldn't Edit 700 1985

          posted by  aleekat on  Tue May 19 10:24 CST 2020
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          last visit: Fri Oct 24 13:19 CST 2014
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          Original harness had major issues. Check the grounds on top of motor for insulation break down.
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            Couldn't Edit 700 1985

            posted by  brickborg on  Wed May 20 13:31 CST 2020
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            Thanks for the diagrams- I've been missing k-jet.org a lot recently, and those are helpful.

            That said, I was able to test the wiring at the EZK and I have good continuity, as well as realizing that my initial resistance test at the hall sensor connector was done with the ignition on. When I tested it with the ignition off, the resistance value was dead on spec.

            I think in this case, it's mostly likely that ignition timing is my issue, but I'll keep soldiering on.

            Thanks!







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