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Thread: Difficult Ignition Cutout Problem

  1. #1
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Difficult Ignition Cutout Problem

    The 87 Shelby Lancer cuts out like it has a bad HEP. The tach dies in sync with this cutout. I have tried the following with no success.

    Replaced HEP with known good unit.
    Replaced power module with known good unit.
    Replaced coil with known good unit.
    General inspection of cap and wires.

    With the fact that the tach drops out simultaneously, should I be looking at the LM next? I had an alternator which caused a similar issue years ago. I don't have a scope to read the output though, so that's a problem.

    Any and all suggestions welcome. I have to tomrrow and Friday to get this going. Monday starts a new school year...

  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Difficult Ignition Cutout Problem

    Replaced the map sensor
    Replaced the computer.

    I added two grounds where they were missing

    It still cuts out some, it threw a coolant temp sensor code when it did it once tonight. It isn't throwing a code for a speed distance sensor even though it is not hooked up. I'm going to pour over wiring diagrams tonight to get some ideas. Tomorrow I will clean the stock connector which is left by the battery and then check all the factory grounds.

    ETA: the voltage isn't very stable. It flutters just a little. That's making me think it must be something relatively big I'm overlooking.

  3. #3
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    Re: Difficult Ignition Cutout Problem

    Are any codes being thrown? If you have a DMM available, I would switch it to AC millivolts and check alternator ripple with all loads on and vehicle running.
    Also, make sure all the pins at the power module are clean and making a good connection.
    I would hook a fuel pressure gauge up and tape it to the windshield. It would be good to know fuel pressure when this is happening.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Difficult Ignition Cutout Problem

    Thanks for the tip on the Ac ripple this feels more and more like when I had a bad alt. In the daytona years ago. I only get a code 22, but that might be from when I set the timing. I need to reset them and double check that connector anyway. Thanks again for the suggestion.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Difficult Ignition Cutout Problem

    OK, with everything on headlights on high, rad fan , blower motor, rear defrost, the works,it was high .02xv to .05xv AC. With everything off but the rad fan, it was .5v ac. I've never had to measure this before, so I'm off to Google if that's a lot.

    Eta: It looks like what I'm observing is right at the upper limit of what one site suggest the maximum should be. I might try this same test on another car to compare notes.

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    Re: Difficult Ignition Cutout Problem

    Brian,
    Sensors are funny on our ECU. My 87 Sundance 4 or 5 years ago was acting odd with errors such as MAP, HEP, TPS were popping up...
    The solution was the O2 sensor.
    I assume the LM and PM were from a known good and the caps are good.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Difficult Ignition Cutout Problem

    Quote Originally Posted by chromguy View Post
    Brian,
    Sensors are funny on our ECU. My 87 Sundance 4 or 5 years ago was acting odd with errors such as MAP, HEP, TPS were popping up...
    The solution was the O2 sensor.
    I assume the LM and PM were from a known good and the caps are good.
    The LM and PM have run a car very well this summer. I might try a TPS next since it has on occasion coincided with throttle input. I've thought that to be coincidence, but perhaps not. I'll try that next and report back.

  8. #8

    Re: Difficult Ignition Cutout Problem

    Have you considered that you might have a wiring problem?

    Have you determined what you are losing? ie. Are you losing fuel? Are you losing spark?

    I would try doing some light pressing on the wiring harness with the engine running. See if it stumbles. Might also try tapping on the ECU...

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    Re: Difficult Ignition Cutout Problem

    Quote Originally Posted by c2xejk View Post
    Have you considered that you might have a wiring problem?

    Have you determined what you are losing? ie. Are you losing fuel? Are you losing spark?

    I would try doing some light pressing on the wiring harness with the engine running. See if it stumbles. Might also try tapping on the ECU...
    I have considered it, and that could be the case, but I went through everything recently and it seemed to be in good shape. I'm pretty sure I'm losing ignition since the tach cuts out when the problem occurs.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Difficult Ignition Cutout Problem

    pull on the fusible links?

    deoxit the power module and LM connectors and bend the tabs back in a touch?

    ASD circuit connections?

    When I have any issues, its usually with a 35 year old connector than a actual part failing.

    Brian

    - - - Updated - - -

    oh and since the LM sends the signal to the tach, it could be flaky power to the LM.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  11. #11
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Difficult Ignition Cutout Problem

    also steering column/horn switch/ignition switch..... when frank would honk the horn in his CSX, it would cut out or stall. there could be gremlins in there too.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  12. #12
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    Re: Difficult Ignition Cutout Problem

    Quote Originally Posted by Aries_Turbo View Post
    also steering column/horn switch/ignition switch..... when frank would honk the horn in his CSX, it would cut out or stall. there could be gremlins in there too.

    Brian
    YUP, this happened to me too.....but I think mine is fixed now as it has not returned for months!
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Difficult Ignition Cutout Problem

    Interesting. I have done the Deoxit thing to pretty well every connector, but I haven't bent any of the tangs yet. I did replace the TPS today and it didn't make a difference. I'll try pulling the horn relay if I can get to it easily enough on the way home. I doubt that's it, because I don't have a horn button hooked up. You never know though. I've been trying one thing at a time so I'm not wondering what solved the issue. It's bad enough wondering if I got lucky on a short drive, let alone if it was one of 2-3 things. Good times.

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    Re: Difficult Ignition Cutout Problem

    After installing a new external voltage regulator to take care of the fluctuating voltage problem, the cutout still persist. I'm going to try a different battery in the car in the next couple days,and if that doesn't do anything for me, I'll replace the ignition switch.

    When the car cuts out I will illuminate the check engine light. No codes are stored, which is very frustrating.

  15. #15
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    Re: Difficult Ignition Cutout Problem

    Did you try new caps yet?
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Re: Difficult Ignition Cutout Problem

    Not yet. The one on the lm is 220uf at 10v. Do you know what the ones in the PM are by chance?

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    Re: Difficult Ignition Cutout Problem

    Swapped batteries today. No real change. I think I'm going to run new wiring from behind the battery to the hep connector. I plan on replacing the connectors with some Deutsch connectors. I've done it before and it seems like the right move given how long a hep usually lasts me. The couple bucks in terminals per hep isn't too bad compared to not knowing for sure what is going on. If I get too much further into this it will be time to purchase another oscilloscope.

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    Re: Difficult Ignition Cutout Problem

    Quote Originally Posted by cordes View Post
    Not yet. The one on the lm is 220uf at 10v. Do you know what the ones in the PM are by chance?
    Yes they are both 220uF at 25V.
    Also have a look at the large white wire wound power resistors..They can crack or rusted out leads
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Re: Difficult Ignition Cutout Problem

    OK. I'll order up a batch of Nichicon 220uf 25v caps and go from there. I have a new ignition switch to try before I rewire then hep. From there it will be the caps in the PM and then perhaps new wiring from the hep all the way back to the source. Of course, some might suggest that a smec conversion is long over due.

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    Re: Difficult Ignition Cutout Problem

    If anyone has a link to some of the axial units, I would appreciate it. I must be searching for them incorrectly on Amazon. The radial units turn up with little issue.

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