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Thread: ??!! Burned Out 2 SMEC's In 10 Miles !!??

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    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    ??!! Burned Out 2 SMEC's In 10 Miles !!??

    RedBox is an 85 GLH-T running 89 TII wiring from a Lebaron GTC, it's recently assembled and has about 2K miles on it's current set up. It made it from SDAC 26 in Memphis to Flagstaff AZ thanks to Rhymes-with-Tortoise X2 where it burned out the SMEC 'driver' board. It does have a socketed 'brain' board and custom cal but that board seems to be surviving just fine. I replaced the driver board with a spare after dragging RedBox home from PHX area on a car dolly, threw the replacement driver board in it and after just a few miles it bucked a couple times then lost all power. No spark, no fuel and curiously the ASD relay is clicking like mad. This is the exact same thing it did in flagstaff a few days and about 10 actual driving miles ago. Even bypassing the ASD does nothing, still wont run.

    So before I throw ANOTHER driver board at the problem(there is nothing visually wrong with either board), Id like to figure out the cause-usually the hardest part I'm thinking a crossed or chaffed wire? The harness has been gone thru for this build, wires checked visually and entire harness retaped.

    Any ideas on the cause or places to look? So far Iv'e just checked the injector harness behind the valve cover but don't see any issues there. I suppose I should be checking for continuity or Ohming everything out but I'm not very good with electrical

    This is a shot of the 'test' just plugging the small 12 pin harness to another SMEC before disassembly and reassembly into the in car SMEC. It fires right up like this and I suspect when I do this type of test again today it will too. I'm going to Cars and Coffee right now (WHERE REDBOX WAS SUPPOSED TO DEBUT TODAY) then a funeral for a coworker so I wont be able to test anything for several hours. Hopefully I'll have some good suggestions by then
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    Supporting Member Turbo Mopar Contributor
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Hi Alan, This give me butterflies...
    rather than fry another driver board, I would suggest to test a non functional one to help determine the root cause of the failure. I am not an expert but I want to help.
    I just reviewed my 88 powertrain diagonostic book, 88 wiring diagram and also the 87 Power module electronic schematics. What I can see, the driver provides clean +8 V in addition to driving the ASD,coil, alternator and injector.
    Checks on 14 way
    Pin 1 is +8V output
    pin 2,6,7 are grounds
    pin 3 fused J2 output
    pin 4 12V from ignition
    pin 9,10 injector control
    pin 12 coil control
    pin 14 alternator control

    So lets first check if the ASD is active and 12V is present on the +coil terminal. Check to see if the -coil terminal is pulsing during cranking. Also check pin 9 and/or 10 for pulsing during cranking as well.
    Last edited by chromguy; 07-09-2016 at 11:07 AM.
    Regards,
    Miles

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

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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    I'd double check the grounds, make sure the coil isn't pulling to many amps and check the impedance of the injectors.


    Working on clearing the decks.

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    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Just getting home now, great tips on the to-do list for tomorrow, Wait, how do I use my DVM again?? Hate electrical

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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    Supporting Member Turbo Mopar Contributor
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Keep us in the loop and good luck
    Regards,
    Miles

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

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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    I agree with Gary on checking the grounds. But also where its grounded is important too. Have you ever notice all of the engine management grounds are in one central spot on the engine? Centrally located grounds prevents high current feedback though wiring, modules, possibly burning out components. If a ground is lost elsewhere in the vehicle, the ground current could find another path through two grounds of the engine management system. I mention this because you updated to a SMEC. Also avoid adding any additional electrical items and taping into the engine management wiring. And lastly check your engine to body ground by doing a voltage drop test. A ohmmeter won't tell you much. There are many videos on YouTube that shows how to do a voltage drop test.
    Last edited by marc; 07-10-2016 at 10:31 AM.
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    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    I was just thinking that a wideband was added just before the package was completed, I'll check the firewall penetration for chafing there too. I'm working with just one arm tho, I blew out a C6/C7 cervical disc acting like a dipsh!t half my age. Those powered by JetSki water jet lifting rides are super fun-until it pyle-drives you into the ocean with astounding force. it was only like a 15' fall but I landed very wrong. Looks like I'm getting some of my own spine hardware in my neck sometime in the next 7 days. Ironic no?

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    Hybrid booster
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Let me know how that turns out youngster, G.L with it. Maybe you can sell some of your hardware to an ole' guy

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    Supporting Member Turbo Mopar Contributor mopar-tech's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Quote Originally Posted by 2.216VTurbo View Post
    I was just thinking that a wideband was added just before the package was completed,
    Is the wide band feeding a narrow band voltage to the ECU? I'd look at that close.


    Working on clearing the decks.

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    So you're actually blowing out the power module portion of the SMEC (Single Module Engine Controller. Combines the previous Logic Module and Power Module into one case). If you open that case you can replace just the Power Module. I've had to replace just the Power Module portion for a customer because only it (PM) was bad and I had an extra one lying around.

    Lots of great tips from everybody so far. I just had an 86 Omni converted to T-II with a bad Power module. Since I didn't want to have happen to me what happened to you (plug in a new one and blow it) because the car sat for 10 years and I didn't know the history behind it, I had to go through and pin out and check the harness and what plugs into it to make sure it was good. Sucked. Like Gary said, if you have an item like a coil or injector that's bad causing a larger draw it can stress the board. And again, bad grounds can do the same thing. So basically you have two wires chaffed together or a bad injector or coil drawing to many amps.

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    After i recently had a coil driver go out on an SBEC and had to buy one from Gary (thanks) i put a small inline fuse holder in the harness just outside the SBEC connector to try to make sure i wouldn't have to buy any more. This doesn't help you until you identify what part of the board is failing, though.

    Dont push the red button.You hear me?

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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Quote Originally Posted by 2.216VTurbo View Post
    Looks like I'm getting some of my own spine hardware in my neck sometime in the next 7 days.
    I wish you a speedy recovery!
    [SIGPIC][/SIGPIC] 86 Daytona Turbo Z C/S with a full 89 Shelby swap, back on the road and soon to be painted (and lose that Oggie Fisher black) 83 Porsche 944, 5 speed, all stock. 2014 Toyota Tacoma 4x4, 5 speed, daily driver. 2017 Trek 1.2 bicycle.

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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Quote Originally Posted by 2.216VTurbo View Post
    I'm working with just one arm tho, I blew out a C6/C7 cervical disc acting like a dipsh!t half my age. Those powered by JetSki water jet lifting rides are super fun-until it pyle-drives you into the ocean with astounding force. it was only like a 15' fall but I landed very wrong. Looks like I'm getting some of my own spine hardware in my neck sometime in the next 7 days. Ironic no?
    sorry dude though i cant say im surprised.

    i could use some of your spine hardware.... L5/L4 goofiness and something up new near the shoulder blades. oh well

    good luck dude

    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.

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    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    So nothing obvious, no grossly visible chafing on O2 sensor or WB wires. No, I didn't get pin by pin serious with a meter yet. I've heard from patients year after year about their arm/neck pain when it's a spine injury. It's interesting because it's such a complex pain. In my shoulder its a red hot ice pick being stabbed in repeatedly and in my arm and forearm its and ice cold vice that is squeezing the life out of my muscles. Oh, and I can't feel my index finger and thumb

    Brian the shoulder blade thing is called subscapular pain, classic spinal stenosis/herniated disc symptom.

    The bulge between C6-C7 is the culprit, that's the crabmeat like disc material that has extruded out thru the torn casing (the Annulus) that ordinarily contains it.
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    is that a fracture on c6?

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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    No Fx, just old man spine with degenerative changes

    So If I am gonna just add a chassis ground to the SMEC, which pin/color wire should should I tap into?

    There is a lotta red paint under the main negative cable ground under the batt tray so I'm gonna make it clean and shiny like Gus always said to

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    OK, clean and shiny grounds X4, every chassis ground I could find I scraped red paint off of and made it nice, even added an additional chassis ground from the negative side of batt. Replaced the 'power module/driver' in the SMEC case and it doesn't fire

    Any Ideas why the ASD just clicks like mad?? I swapped a known good one in from the rampage RT (which actually had to be modded to fit? Little tang on the 89 harness the RT harness doesn't have) and it just click click clicks as soon as the key is powered up to run position.

    Gary, how do I check for that feedback voltage you mentioned, which pin *shouldn't* have that feedback?

    AJ (no More Alan) 84 Rampage RT TIII/568 Quaife 87 GLHS dealer optioned Red 16V Masi/568/Quaife
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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    The only idea I had was injector impedance too. I sure hope you recover quickly from your neck problem. I hope you really upswell this one.

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    Quote Originally Posted by 2.216VTurbo View Post
    Any Ideas why the ASD just clicks like mad??
    When I first started socketing boards, the first one I did caused the ASD relay to click on and off like crazy and the tach needle to jump all over the place. The Logic Module board ended up being bad. I don't know what caused it, my technique in removing the chip, static electricity, who knows. There's been other times I'd burn a chip and the data getting corrupt and causing the same issue. If the ASD relay is clicking I'd say you have a bad Logic Module this time or a bad chip.

  20. #20

    Re: ??!! Burned Out 2 SMEC's In 10 Miles !!??

    That clicking happens when the fuel rail ground isn't connected, not sure about any other reason. That thing grounds 6 pins on the SMEC. As for the injectors, our systems run low impedance. Hi impedance injectors are easier on the drivers and will run just fine.

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