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Thread: familiar song...SC sat for years, won't start, running out of ideas & things to test

  1. #16
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    Fuel pump connectors are good (just changed pump) and on MY SC at least, there isn't a fuse for the ECU in that fuse box under the hood. The fuse map on the back of the lid says *Except 3.8 SC

    Again, I have fuel pressure, and the ECU is working.


    Yesterday I changed plugs and wires. Same result in that I can pick up a signal with my timing light on the drivers side wires only. If I test the passenger side wires I get nothing, even right by the coil. Very odd. All six posts of the coil DO give spark when I put a tester on them.

    I keep coming back to either weak spark ie bad coil but the coil has been swapped with a known good one, or bad grounding on the passenger side cylinder head causing the plugs on that side to not be grounded well enough. Sounds nuts to me but I can't come up with anything else right now.

    Today I will go through the dis-no-start check list, in full this time.

    Question for anyone who knows: Is it thermal paste or dilectric grease that's used on the DIS? I've seen both mentioned but they do very different things. If it's thermal paste....where have you found it in quantity? I've only ever seen small syringes of it for computer chips.

    Thanks

    K

  2. #17
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    About that paste....you're right. But this isn't about what each is typically spec'd for.

    'dielectric': having the property of transmitting electric force without conduction; insulating.

    ...in the case of the DIS, the only electrical component at work between the DIS and the pedestal is the ground path from the corner lead(s) on the DIS, thru the mounting screws, and down into the pedestal. Otherwise, there is nothing electrical to insulate, and nothing to conduct.

    As for the heat at work, the pedestal is hotter than the DIS when the engine is at temp. The compound's job is to prohibit hot spots on the DIS that can damage it's internals.

    In my opinion, dielectric's basic properties can perform the job as needed. An exotic computer chip/heatsink compound will do the same thing, but is not required. What is required is a thin coat of something that can establish a thermal coupling between the two and remain stable at temps.

    As a bit of a side note, it's clear Ford struggled with the design/location of the DIS as relates to heat as witnessed by it being moved to the fender in later years (same issue w/it's TFI predecessor). Owners of early model SCs are left to do the best they can, meaning whatever you do, never install a naked DIS.
    Last edited by KMT; 06-10-2018 at 12:21 PM.

  3. #18
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    Quote Originally Posted by KMT View Post
    About that paste....you're right. But this isn't about what each is typically spec'd for.

    'dielectric': having the property of transmitting electric force without conduction; insulating.

    ...in the case of the DIS, the only electrical component at work between the DIS and the pedestal is the ground path from the corner lead(s) on the DIS, thru the mounting screws, and down into the pedestal. Otherwise, there is nothing electrical to insulate, and nothing to conduct.

    As for the heat at work, the pedestal is hotter than the DIS when the engine is at temp. The compound's job is to prohibit hot spots on the DIS that can damage it's internals.

    In my opinion, dielectric's basic properties can perform the job as needed. An exotic computer chip/heatsink compound will do the same thing, but is not required. What is required is a thin coat of something that can establish a thermal coupling between the two and remain stable at temps.

    As a bit of a side note, it's clear Ford struggled with the design/location of the DIS as relates to heat as witnessed by it being moved to the fender in later years (same issue w/it's TFI predecessor). Owners of early model SCs are left to do the best they can, meaning whatever you do, never install a naked DIS.


    So the paste is PROTECTING the DIS from the engine's heat, not taking heat AWAY from it ie acting like a heat sink. Makes perfect sense. What about another material that insulates the DIS from conductance of heat through the bracket? Would that work?

    An update on the original discussion:

    I pulled the codes again and got 096 twice. "Secondary fuel pump circuit failure" or something like that. So I started tracing the fuel pump wiring and from what I can tell (please tell me I'm an idiot of I'm wrong), the 'priming' cycle of the fuel pump when you turn the key on is controlled directly by the ECM, but the 'run' funtion has to go through a relay first. So when starting, if the relay doesn't come on the car won't start even though you heard the pump run when you turned the key. Am I right?

    So after starting to go through the fuel pump wiring, I found this black box in the trunk with a pretty good sized harness going to it.

    What is it?

    (stay with me guys...lol)

    Kevin

  4. #19
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    Quote Originally Posted by hulakai View Post
    So the paste is PROTECTING the DIS from the engine's heat, not taking heat AWAY from it ie acting like a heat sink. Makes perfect sense. What about another material that insulates the DIS from conductance of heat through the bracket?
    I demonstrated via thermal imaging, in a previous thread, that the DIS is cooler than the pedestal: http://www.sccoa.com/forums/showthre...35#post1107435 - that thread links to one where an owner lifted the DIS off the pedestal and another discussed relocating it. I've toyed with both ideas, but I don't see a chronic issue that prompts me to take such action...yet. Keep the ground path in mind if you decide to get creative,


    So after starting to go through the fuel pump wiring, I found this black box in the trunk with a pretty good sized harness going to it.

    What is it?
    Does it have a reset button? If so, be sure to push on it, and see my earlier comment #6 above - http://www.sccoa.com/forums/showthre...89#post1117089

  5. #20
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    Quote Originally Posted by KMT View Post
    I demonstrated via thermal imaging, in a previous thread, that the DIS is cooler than the pedestal: http://www.sccoa.com/forums/showthre...35#post1107435 - that thread links to one where an owner lifted the DIS off the pedestal and another discussed relocating it. I've toyed with both ideas, but I don't see a chronic issue that prompts me to take such action...yet. Keep the ground path in mind if you decide to get creative,




    Does it have a reset button? If so, be sure to push on it, and see my earlier comment #6 above - http://www.sccoa.com/forums/showthre...89#post1117089

    Thanks. I apologize for my laziness. I looked up the part number stamped on it and it's the keyless entry control module. Probably responsible for that pesky anti-theft system too. I have definitely checked the inertia switch...probably 5 times by now.

    I changed the fuel pump relay with another one. No change. I disconnected the battery to clear the computer and rechecked. Now there's no code 096.

    So after that I sprayed some carb cleaner into the intake to see if it would sputter at all. Nothing, so I'm leaning away from a fuel delivery issue being the problem.

    Time to go through the DIS-nostart list now that I don't have any codes.

    Can injectors get so gummed up after years of sitting that NONE of them will fire? Seems highly unlikely to me that they could ALL fail from sitting based on past experience resurrecting cars after sitting. They ARE getting signal according to the noid light.

    To summarize:

    Fuel pressure, check.
    Spark, yes but only at the coil and after that it gets inconsistent even with new wires and plugs (see earlier post).
    Injector signal, check.
    Upshift light OFF during cranking, check.

    Fresh fuel and filter
    ECM swapped with another 89, no change
    Cam sensor disconnected, still no start after 3-4 tries
    Crank sensor swapped with another 89 (despite no upshift light), no change

    All that's left (I think) is to check resistances and voltages in the DIS_nostart list.

    K
    Last edited by hulakai; 06-13-2018 at 02:50 PM.

  6. #21
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    Hey guys....hoping there's someone out there who hasn't lost patience with me on this....

    Starting going through the no-start list AGAIN today.

    I pulled all the plug wires and checked for spark. Got spark on all.

    Then I reconnected the plug wires and checked again with my timing light. Even though I had spark on all wires when disconnected, the timing light isn't getting a signal on wire 1 or wire 3, and on wire 2 it's getting a weird double flash i.e. for every time it should fire on that cylinder it's flashing twice quickly instead of once.
    Cylinders 4, 5 and 6 are flashing the timing light normally and consistently.

    Does anyone know what that double flash on cylinder 2 means? (and/or why I would get spark on cylinders 1 and 3 with a tester, but then not see any signal with the timing light on those cylinders?)

    Thanks

    K

    p.s. all new Autolite platinum plugs and new wires too.

  7. #22
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    Quote Originally Posted by hulakai View Post
    Hey guys....hoping there's someone out there who hasn't lost patience with me on this....

    Starting going through the no-start list AGAIN today.

    I pulled all the plug wires and checked for spark. Got spark on all.

    Then I reconnected the plug wires and checked again with my timing light. Even though I had spark on all wires when disconnected, the timing light isn't getting a signal on wire 1 or wire 3, and on wire 2 it's getting a weird double flash i.e. for every time it should fire on that cylinder it's flashing twice quickly instead of once.
    Cylinders 4, 5 and 6 are flashing the timing light normally and consistently.

    Does anyone know what that double flash on cylinder 2 means? (and/or why I would get spark on cylinders 1 and 3 with a tester, but then not see any signal with the timing light on those cylinders?)

    Thanks

    K

    p.s. all new Autolite platinum plugs and new wires too.


    Update: Changed the coil pack back to the original (after swapping with one from a working XR7). Tested for signal on the wires again and got a steady flash on cylinder 3, nothing on cylinders 1 and 2, and the usual steady flashes on 4, 5 and 6 but at TWICE THE SPEED of cylinder 3.

    I thought I read something on another thread about the ECM sending double sparks during the start cycle. Did I imagine that?

  8. #23
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    Quote Originally Posted by hulakai View Post
    double flash on cylinder 2 means?.
    The SC's distributorless ignition system always fires two cylinders at the same time, known as 'waste spark'. The waste spark fires the opposite direction, going from the shell to the center electrode. The coil is actually 3 coils, two terminals each.

    Completely normal, so don't let it confuse you.

    nothing on cylinders 1 and 2,
    Did you notice the no-start N5 list doesn't say plugs 1 & 2? ...they are on different coils. Strange you'd see that if you're working with the right cylinder/plug numbers.

    You've changed coils, plugs, wires and still no joy, so it might be time to move in the no-start check, to N7, I believe, but -not- until you've confirmed N3 & N4, of course.
    Last edited by KMT; 06-16-2018 at 04:56 PM.

  9. #24
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    Quote Originally Posted by KMT View Post
    The SC's distributorless ignition system always fires two cylinders at the same time, known as 'waste spark'. The waste spark fires the opposite direction, going from the shell to the center electrode. The coil is actually 3 coils, two terminals each.

    Completely normal, so don't let it confuse you.

    Ok thanks, I didn't know that. Seems rather lazy of them to have done it that way.

    However, I'm not sure we're talking about the same thing...what I was attempting (poorly) to describe is two pulses on the SAME cylinder/plug wire in quick succession, not two different cylinders firing at the same time. Cylinders 4, 5 and 6 don't do that...they just fire at the same steady rate.

    To try and summarize in more detail...this is what I believe is causing my no start problem. It's not fuel, I'm certain.

    One bank of cylinders (4, 5, 6) receives a spark normally and as expected (based on my timing light). The other bank gets a spark VERY sporadically, not always on the same cylinder, and when it does it's usually two quick pulses intead of one. The spacing between the double pulses are as expected. Again, inconsistent but re-producable.

    It seems to me (and I'm nothing close to an expert) that one half of the coil pack is 'weak' or failing. It's the only coorelation I've found in a LOT of troubleshooting i.e. the pack is divided in two rows the same way that the cylinder banks are. However, I have reproduced these results with two different DIS modules and two different coil packs with at least one of each coming off of a running car. I have a brand new coil pack here, but based on what you've said about how the coils fire, it seems unlikely that it would fire differently from one post than the other.

    I'm quite prepared to continue with the detailed tests in the no-start doc, but with inconsistent spark like this it seems pointless....I'm REALLY running out of ideas now.

    Question: should I be doing all these tests with the cam sensor disconnected just to rule that out? The ECM has a backup timing table it can use, correct?

    K

  10. #25
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    I'm just trying to get you to move on from plugs and wires....you can't diagnose plugs/wires on these cars like you can older models. You can't troubleshoot anything about the SC's ignition system like you can with older models.

    You have a new coil, new plugs and new wires, You're done with them. The next steps in that process will help you check the rest of the system. Do that. Don't over think it, don't get hung up.

    I'm REALLY running out of ideas now.
    That's why we follow factory processes. This isn't about 'ideas'.

    Question: should I be doing all these tests with the cam sensor disconnected just to rule that out? The ECM has a backup timing table it can use, correct?
    I don't recall that process telling you to do that? You have to stop trying to wrestle with the process, and just do it.

    You promised to go thru that process in full, and how you're off on yet another tangent.

    Good luck.
    Last edited by KMT; 06-16-2018 at 07:47 PM.

  11. #26
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    Quote Originally Posted by KMT View Post
    I'm just trying to get you to move on from plugs and wires....you can't diagnose plugs/wires on these cars like you can older models. You can't troubleshoot anything about the SC's ignition system like you can with older models.

    You have a new coil, new plugs and new wires, You're done with them. The next steps in that process will help you check the rest of the system. Do that. Don't over think it, don't get hung up.



    That's why we follow factory processes. This isn't about 'ideas'.


    I don't recall that process telling you to do that? You have to stop trying to wrestle with the process, and just do it.

    You promised to go thru that process in full, and how you're off on yet another tangent.

    Good luck.

    Listen, I understand what you are saying, and I agree with you....BUT the no-start list says in STEP TWO to confirm good, CONSISTENT spark on all cylinders and I'm not able to do yet that so I haven't moved on to the next step.

    What exactly is it that I'm 'hung up' on besides step two in the checklist? If by 'tangent' you are referring to my question about doing these tests with the cam sensor unplugged, I was simply asking if eliminating the cam sensor and forcing the computer to use it's preset timing was a good idea or not?

    I have not installed the new coil, only a used working one. I CAN install the new one if it's the right thing to do but I don't like replacing parts at random just to see if it changes anything.

    So if my current methods of validating spark aren't correct, please tell me how to confirm good, properly timed spark and then I'll move on to the rest of the checklist.

    K

  12. #27
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    Ok so I've gone through the no-start list and found no issues. Spark on all wires using a spark tester. New plugs. Crank sensor good. Wiring from crank sensor to ecm good. Fuel pressure good. No upshift light while cranking. No codes.

    No clue where to go from here. TPS?

  13. #28
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    Quote Originally Posted by hulakai View Post
    Ok so I've gone through the no-start list and found no issues. Spark on all wires using a spark tester. New plugs. Crank sensor good. Wiring from crank sensor to ecm good. Fuel pressure good. No upshift light while cranking. No codes.

    No clue where to go from here. TPS?
    If you've got spark and fuel pressure, the only thing left is the injectors.

    https://www.wikihow.com/Test-Fuel-Injector

  14. #29
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    Quote Originally Posted by TbirdSCFan View Post
    If you've got spark and fuel pressure, the only thing left is the injectors.

    https://www.wikihow.com/Test-Fuel-Injector

    That link doesn't work anymore. Is that a testing procedure for the injector itself? I tested for signal with a noid light (good) but thought it unlikely that ALL the injectors failed at once. The engine isn't coughing or anything when cranking.

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