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Ignition problem

Discussion in 'Wrangler YJ (1986-1995)' started by Nick301, Sep 14, 2021.

  1. Sep 14, 2021 at 3:05 PM
    #1
    Nick301

    Nick301 [OP] Member

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    I’m new to this site but have had my YJ for about 6 yrs. I’ve had no serious issues just preventative maintenance. A few weeks ago I drove across some rumble strips set out by the highway dept. The engine just shut down completely and has not started since. It has spent several weeks in a garage where they’ve replaced the following: ignition module, ignition coil and 2 ea relays.
    It appears there isn’t fire getting to the plugs. I’ve tried carb cleaner and starter fluid with no ignition.
    I’m looking for help to troubleshoot this problem.
    This is a 2.5, 4 cyl, throttle body, standard shift.
    Nick
     
  2. Sep 14, 2021 at 6:09 PM
    #2
    Groundfault

    Groundfault Well-Known Member

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    Do you have output at the distributor end of the coil wire?
     
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  3. Sep 15, 2021 at 5:18 AM
    #3
    Awrench

    Awrench Well-Known Member

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    might want to find another shop.

    ANYWAY IIRC a 1989 is a renix system. Somewhat quirky but think of it as early computer controlled systems.
    The place I would look is 'engine speed sensor' thats the renix name for a CKP - a Crank Position Sensor. Located on bell housing.

    Let me know
     
  4. Sep 15, 2021 at 5:36 PM
    #4
    Nick301

    Nick301 [OP] Member

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    I’ve checked a number times for any kind of spark with no result. NoSpark.
    Today I replaced the CPS with No help. Chilton book indicates there is a Cam Position Sensor but I can’t find it. My next plan is to pull the ignition switch just to check continuity. I’m waiting for another mechanic to get back in his shop.
     
  5. Sep 16, 2021 at 2:51 AM
    #5
    Awrench

    Awrench Well-Known Member

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    Have you found out if a renix or not?

    I think i mentioned quirky the old systems. A CMP is also called a SYNC SIGNAL GENERATOR.
    Also you changed a CPS that is ENGINE SPEED SENSOR, AND the correct acronym is CKP.

    With key on is there 12v at coil? You MAY Need to check within @2seconds of turning key to run, then PCM will deenergize.

    CMP.jpg
     
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  6. Sep 16, 2021 at 5:26 AM
    #6
    Nick301

    Nick301 [OP] Member

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    Here comes a true test of my knowledge of modern terminology!
    I’m don’t know the term “renix” but after my ‘65 Chevy I quit doing more than basic mechanical repairs. My skills are limited when chasing electrons.
    Also what is a PCM?
    Later today I’ll do the voltage checks.
    Thanks for your help thus far.
     
  7. Sep 16, 2021 at 8:23 AM
    #7
    Awrench

    Awrench Well-Known Member

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    RENIX - As I mentioned the early days is computer* controlled systems.
    >> Renix was the "brand" name of the PCM system" Think delco remy to GM.

    Check for 12v at coil - when key moved to RUN or start.


    * Car computers PCM, Powertrain Control module. There are other computers on todays vehicles ECM, BCM, VCM, etc
    PCM = Powertrain Control Module
     
  8. Sep 17, 2021 at 2:54 PM
    #8
    Nick301

    Nick301 [OP] Member

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    Thanks for the information. I haven't given up just yet.
    First, I haven't found anything resembling a computer like one on my GMC but can't rule out there could be on somewhere.
    1st photo: I disconnected the 2 connectors. With inginition "on" there's 14.6 volt at the "yellow" wire only.
    2nd photo: with coil removed, ignition "on" there's 14.6 volts at the top clip. There's 9 volts at the bottom clip. No power at the center clip.
    Reinstalled the coil, no spark at the distributer wire.
    Both the module and coil are new. The coil appears to olm out correctly.
    Monday I'll take the jeep into the garage for his input.
    20210917_123111.jpg 20210917_131911.jpg
     
  9. Sep 18, 2021 at 1:43 AM
    #9
    Awrench

    Awrench Well-Known Member

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    I will follow up soon having laptop issues
     
  10. Sep 18, 2021 at 3:07 AM
    #10
    Awrench

    Awrench Well-Known Member

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    Sorry busy day info will come in pieces as I get time.

    Your vehicle comuter - PCM or ECM (Renix) is located by the gas pedal and heater (HVAC) box.
    The ICM you attaced photo - see attachments is simple - power, ground, and control.

    GTG will get back with test
     

    Attached Files:

  11. Sep 18, 2021 at 9:08 AM
    #11
    Nick301

    Nick301 [OP] Member

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    20210918_094759.jpg
    One of the attach flange was broken. May have caused excess vibration.
     
  12. Sep 18, 2021 at 9:34 AM
    #12
    Awrench

    Awrench Well-Known Member

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    OK you checking things out... That is Emissions Timer NOT the ECU* aka PCM.
    see attachments.

    Remember I mentioned - system is OLD, quirky and over 30 years of previous owners fixing it.

    I am trying to get a easy fast ignition test...

    *ECU is old speak PCM is the todays often used acronym.

    Timer module.jpg
    ECU, PCM, renix.jpg
     
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  13. Sep 18, 2021 at 1:46 PM
    #13
    Awrench

    Awrench Well-Known Member

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    here is a test -

    look at diagram remove both connectors the 1 wire and the 3 wire.
    With key on engine off (KOEO)
    1) is there ANY voltage on the single connector Black Red wire?
    NO voltage is what we want.
    2) Is there 12v 3wire connector YELLOW wire?
    12v is what we want
    Use a test light between the yellow wire and the black red wire.
    Try to start engine - did the test light flash on and off?
    YES is what we want -

    SORRY explaining and doing 2 different things - testing takes moments- explaining and working over the internet, forever.

    Will explain after you answer and got on to next step

    test.jpg
     
  14. Sep 18, 2021 at 4:01 PM
    #14
    Nick301

    Nick301 [OP] Member

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    Battery=14.6 volts
    Key "off"--red/black=no voltage
    --yellow=6 volts
    Test light--attempt to start=no flashing
     
  15. Sep 18, 2021 at 4:06 PM
    #15
    Nick301

    Nick301 [OP] Member

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    FYI, with key "on" yellow wire voltage flashes 0 -6 volts
     
  16. Sep 18, 2021 at 4:48 PM
    #16
    Awrench

    Awrench Well-Known Member

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    that is the issue - that should be 12v.
    SO - we need to chceck wiring -IIRC the ASD (Latch relay) supplies the voltage.
    If yiou feel ambitious as I search the books - With KOEO check the voltage at fuel injector - leave it plugged in both wires should be 12v. I suspect there may also be the 6v issue.

    SORRY - a weekend and Sunday is Church, BBQ, bourbon, football.... I will try and look into this.
     
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  17. Sep 18, 2021 at 5:07 PM
    #17
    Nick301

    Nick301 [OP] Member

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    Thanks, really appreciate your time and help. 30 yrs of acft maint i was very confident but tech data was vital. Haven't located the PCM but did find a thread indicating it could be behind the glove box. Still looking and will check fuel injector volts. Enjoy tomorrow.
     
  18. Sep 18, 2021 at 5:32 PM
    #18
    Groundfault

    Groundfault Well-Known Member

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    My factory one was behind the glove box above heater box (87 YJ). 5.7 Chevy ECM went back in the same spot.
     
  19. Sep 18, 2021 at 5:34 PM
    #19
    Awrench

    Awrench Well-Known Member

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    yes behind glove box is a possibility - on top of heater box.

    Back to the yellow wire - in reply #8 above you had battery voltage @14.6.
    Now you claim same wire is @6volts?

    that is supplied from the ignition switch. see attachment YELLOW highlights beginning of the yellow wire to ign module

    30 yrs aircraft maint - what did you work on?
    Retired F15 crew chief.
     

    Attached Files:

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  20. Sep 18, 2021 at 6:43 PM
    #20
    Nick301

    Nick301 [OP] Member

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    Well guess I better do some digging, back track to ignition sw.
    Retired crew chief, F-4CDE, 111B, T-38, F-16blk30. Got too old.
     
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