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Thread: My '77 Z Coupe dies on the road when I see the tach jumping between Redline and Zero

  1. #1
    Wing King jthill3's Avatar
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    Default My '77 Z Coupe dies on the road when I see the tach jumping between Redline and Zero

    This has happened at 50 MPH and when slowing down at a redlight. The tach goes crazy and then the car quits.

    If the car is moving, it restarts itself.... when I slow down for a redlight and it quits, I am able to restart the car and continue on.

    I have been told this means the Ignition Module is dying.

    Do ya'll agree? If so where can I get an Ignition Module for a 1977 280Z Coupe, base model.

    Thanks for any help

    Tommy
    678-763-6939
    jthill3@att.net

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    Yes, those are all typical signs of a failing module. Some of the auto parts stores can get replacement modules, or try Black Dragon, Motor Sport Auto, or Zpecialties.com. They're expensive though, in the high hundred or two hundred range.

    The wrecking yard is another option, or an aftermarket ignition module, like the GM HEI module. Or you could swap to an early ZX distributor with an E12-80 module. But you will lose the temperature controlled 6 degrees of timing advance, since the factory module is designed to use the two pickups in the distributor. Unless you have a California model.

    Quickest might be a wrecking yard 75-77 module, if you can find one. They're mounted up above and in front of the fuse box.


    Edit - Got curious. Change the hundred and two hundred above to three hundred and four hundred - http://www.oreillyauto.com/site/c/se...80Z&vi=1209248
    Last edited by Zed Head; 03-05-2012 at 12:39 PM.

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    Rust Free'ish zKars's Avatar
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    You have either a loose connection somewhere in the ignition wiring to and from the ignition module, at or in the distributor, or from the power supply wiring that feeds it all. More likely, you have a bad ignition module internally. Pretty tough to diagnose an intermittent problem like this.

    Could even be the tach itself. If its shorting its sensor line to ground internally, it would kill the ignition. So step one, disconnect the tach from the circuit by unplugging the in-line resistor in the harness below the glovebox against the fire wall (blue tape around a black rubber nubben about the size of your thumb), do without the tach for a bit and see if the problem persists.

    Put a want to buy add in here for a module. Lost of folks have replaced there stuff with later dizzy's from ZX's and other aftermarket solutions. I have one, but I'm not likely the closest person to ya!
    Last edited by zKars; 03-05-2012 at 12:15 PM.
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    Pretty sure the engine won't start without the inline resistor. I had mine unwrapped and it fell out once. Not even a pop until I put it back in (no CSV, so no fuel supplied at all without the injectors firing). Fun to try though.

    I've had two engines, also, that wouldn't start without the tach connected.

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    Registered User Willoughby Z's Avatar
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    Rock Auto has 'em for less than $140.

    HLS30 371-239 (1/77)
    Every time he touched her, she told him that places where she wanted to be more beautiful!
    Mr.Tamura said it is like an old craftsman of Buddha statue,he did not creat it, Buddha itself...
    Kats

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    Former frequent poster sblake01's Avatar
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    If it does turn out to be a bad module, a 77 module might be a tough find and somewhat pricey. You could do the GM HEI module conversion for much less money. I believe Sarah (FastWoman) converted hers so she should be able to supply the info.
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    Registered User Willoughby Z's Avatar
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    Search> GM HEI upgrade

    HLS30 371-239 (1/77)
    Every time he touched her, she told him that places where she wanted to be more beautiful!
    Mr.Tamura said it is like an old craftsman of Buddha statue,he did not creat it, Buddha itself...
    Kats

    FSM: http://www.xenons30.com/reference.html
    EFI "bible" : http://www.4moores.com/280z/files/280zfuelinjectionbook.pdf

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    I have had a similiar problem with 1977 Datsun Z's before. Check the ignition relay up underneath the fuse block on the passenger side interior. Either try to repair the old one or buy a new one for 100 dollars or more.

    Cheers

    jar

  9. #9
    Z geek at large FastWoman's Avatar
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    Monkey see, monkey do...

    http://www.zhome.com/ZCMnL/tech/gmhei.html

    It's a funky diagram, but clear enough. My module was about $11. I mounted it on the fender where the distributor pickup coil connects.

    I'm betting on a bad connection or short, though. The fact that it happens when you're rolling to a stop is very suspicious.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    If he pushes the clutch in when slowing down then it fits my module's symptoms.

    When mine was dying I could make it go bad by winding the engine up to ~3,000 RPM or greater. Then the tach would start jumping around, and reading a much higher RPM than estimated by road speed and gear. It wouldn't idle well or would just would die if I pushed in the clutch. But it would still go down the road if I stayed in gear with the gas on, tach needle vibrating and reading wrong. If I stopped and let it die it would start right back up and be fine until I revved it over ~3,000 RPM again.

    Just a few more signs to compare.

  11. #11
    Z geek at large FastWoman's Avatar
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    FAIW, if the tach redlines, it probably also means the ECU is dumping lots of fuel through the injectors. (Both are triggered off the same signal.) I suppose the engine could die from being flooded.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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