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Thread: DIS Testing Procedure

  1. #1
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    DIS Testing Procedure

    Hey guys,

    Can anyone post the procedure to test the DIS module for my 91? Trying to figure out the dreaded no start. Have fuel and spark at the coil. I have a box of DIS modules and need to know which are good. Thanks.

  2. #2
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    Not sure there is a reliable way to test off the car (without special tools/breakout box etc.). See this previous thread for discussion otherwise.

    http://www.sccoa.com/forums/showthre...st+DIS+off+car
    Last edited by KMT; 06-19-2019 at 11:49 PM.

  3. #3
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    Thanks dude.

  4. #4
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    The only real way to test the DIS module is to confirm all the inputs and outputs, so verifying signal from the cam and crank sensors, and confirming correct resistances on the ignition coil, and all the wiring between all of them. In practice, it is much easier to just swap a known good one in and see if it fixes the problem. Also given that they can and often do fail without warning, having a spare one in the glove box is not a bad idea, and they aren't that expensive, so I would say pick one up and swap it out and see if it fixes the problem.

  5. #5
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    Quote Originally Posted by MadMikeyL View Post
    I would say pick one up and swap it out and see if it fixes the problem.
    He said he already has a box of them...the question was how to test those.

  6. #6
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    State side most local parts stores have testing equipment and can check them in house for free. Not sure if that's the same up north.

    -Tim
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  7. #7
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    Cool

    Quote Originally Posted by Tim Groth View Post
    State side most local parts stores have testing equipment and can check them in house for free. Not sure if that's the same up north.

    -Tim
    AutoZone used to test them here in the PNW, with vague success...about 4 years ago they went full stop and declined to test them at all. This was about the same time the price fell dramatically, and with lifetime warranty, the last time I had doubts on one I'd bought from them, they just gave me another.

    I've a bag full of used ones I haven't touched in a long time, and I'm currently trying to come up with a better way to bench test, however, as that would involve feeding it live signals and getting it up to temperature, on-car testing is still easier, but not as easy as taking advantage of a free replacement warranty, so...

    My goal with being able to reliably bench test is still on due to anticipation of these being obsoleted any day now, and when that day comes, a warranty won't matter.

    About DIS fails, since we're on the subject - I think the reason it's common to have a box/bag full of spares is that the DIS gets side-eye as culprit when swapped and things work better because of other issues, such as a compromised harness or marginal grounding. Simply swapping one out can cause changes in those, making it seem like the DIS was the problem, when it was just caught up in the root cause. I wonder if any of the spares I have include one hard fail, but that day will come, and that box of spares will be money in the bank when these things are no longer available, just like the early crank sensors.

  8. #8
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    Quote Originally Posted by MadMikeyL View Post
    In practice, it is much easier to just swap a known good one in and see if it fixes the problem. Also given that they can and often do fail without warning, having a spare one in the glove box is not a bad idea, and they aren't that expensive, so I would say pick one up and swap it out and see if it fixes the problem.
    I concur.

    I'm going thru this right now with my DD. It has been just dying on me usually at a stoplight. Sometimes it will restart, but not always. No codes set, other than cam sensor code, which I replaced. I went thru and swapped out the IRCM, since the abrupt cut out might be a fuel pump or EEC relay. Then I swapped out the EEC itself. I swapped in an older DIS (labelled as unknown) and got a coil 3 circuit failure code (which confirms it was bad). Now I've got a known working DIS from my 5 speed and so far, so good.

    So the moral of my story is test each one by running with it installed, but keep another spare on hand.

  9. #9
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    I think I picked up a whole ~~~~ load of them when I encountered the first DIS failure in my brother's car. Agree on the "swap out the DIS" procedure. I don't believe we have any shops capable of testing them but I will call a few auto electrical specialists on Monday.

    As a background leading up to the no start. I had David tune the car when he was here. I drove it afterwards for almost 3 months. It sat for a few days and when I went out to park it for the winter, it wouldn't start. It has had this gremlin since I bought it from John. This being the third time it has refused to run with no real cause found.


    So we have been going through the check list with ~~~~ for luck. When the key is turned to the run position, the upshift light stays on, check gauges stays on and the check engine light stays on. When you turn the key to start, the check gauges and check engine lights stays on and the alarm light flashes . I can't remember if the alarm light went out while cranking before as it has been awhile. I read a post on one of the boards that said it should go out when the key is in the ignition and cranking. Perhaps someone can chime in on that.

  10. #10
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    The linked thread above includes this link for a no start check...did you do any of that yet?

    Not the alarm light, it's about if the upshift light is on while cranking to start - if so, that points to a bad crank position sensor. Be sure to check the balancer to see if it wants to leave home.

    About the alarm light...does the car have a 3rd party alarm? Some of them have the ability to kill the start circuit - I'd check it out to see if it's involved.
    Last edited by KMT; 06-21-2019 at 09:52 PM.

  11. #11
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    I called it the check list and yes been going through it. Got to a change DIS portion and tried going through a couple before we shut it down for tonight. Weather sucks and makes my bad hip hurt.

    Alarm is factory Ford. I have a remote start from Command start. The upshift light does go out upon cranking. I got two extra CP sensors from John as well as an IRCM he tested and another ECM. Balancer is a BHJ with about 500 miles on it. Haven't tried the ECM yet but I think it is DIS. Might try to get a known working one from John to rule it out.

  12. #12
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    Quote Originally Posted by Flex View Post
    I called it the check list and yes been going through it.
    Ah, yes, of course, thanks. BTW, any time you pull a connector, be sure to check it for corrosion, loose pins, missing keepers, etc. Same with grounds...take them off, clean if possible, replace if any question.

    Good on you for having spares to lean on. Sounds like you'll get it sorted soon enough.

  13. #13
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    When I first bought the car, I put dielectric grease in most of the connectors so they are corrosion free. Haven't noticed anything loose but there are a few connectors on the harness that were melted before. Where are all the grounds located? I haven't looked into those yet. The large plastic line that goes to the evaporative cannister is broken and have not had a chance to fix it yet.

  14. #14
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    Grounds...

    Tons, from the center bolt at the ECU, to the short cable from the pass. side motor mount over to the body, to the single wire that grounds the injectors that hides on the rear of the driver side head, to the duo of ganged grounds on the header panel next to the top/front of the radiator, to the thick wire that is bolted to the header panel right in front of the battery, just to mention a few.

    Some owners that have painted the heads and accessory brackets find a no-start when they put it all back together due to the paint blocking the ground paths. The rear bolts on the DIS are it's ground into the bracket, then the engine block, then the cable at the motor mount.

    Shielded wires in the front upper harness complete a path back to the ECU.

    Given it's reliance on electronics means the SC lives/dies on it's grounds - the age of these cars means more attention than usual when they are involved, I think.

    Corrosion can hide inside a sheath, so even if the end looks clean, there can be hidden resistance. The body ground mentioned above can hide corrosion between the bolt and the threads in the panel, but my advice is that if you take it off and it's not new, to not bother putting it back on, replacing it instead.

    Know how to test for voltage drop at a ground?

    Do you have any factory manuals, including an EVTM for that year SC? It will have all the details.

    That busted line at the evap could be a significant vacuum leak...pain to get to, but can't be left that way. Speaking of vacuum leaks, a smoke test is a great way to flush them out.

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