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Thread: MSD-8 Plus intermittent no start.

  1. #1

    Default MSD-8 Plus intermittent no start.

    We have an intermittent problem with our new 7805 MSD-8 Plus. It occasionally doesn't trigger the coil while trying to start (no flashing LED on box and nothing at the coil). I've done the usual momentary grounding test. There's still no spark at the 8261 coil, cranking or not cranking the engine. I also tried another coil, but felt it couldn't be that with the LED not flashing. We did the usual (back to basics) Ohms test every wire that could feasibly be an issue, checked all inputs and outputs, especially grounds, and keeping circuits separated. (I'm a stickler when it comes to wiring and have been running this same combination since 2006 and has never failed.)

    It's being triggered from our trusty Motec M800 (same setup since 2006). Being an important low voltage circuit I did give it a lot of attention. Because it failed the trigger test, it's hard to blame the Motec or the trigger wire. Also, as an example of the Motec & wiring being intact, we also have our backup 7531 Digital 7 that we put back into use to make the next round. We've wired both units with the same Deutsch DT connectors, so we can do a quick plug & play and A-B-A test. Fortunately, the Digital 7 ran without any issues, as it always has.

    Note: The problem only happens on startup (once it's running, it doesn't have an issue). And yes, one of the first things we checked was to monitor the battery voltage on start. The engine has very low cranking compression, so voltage drops very little when cranking. We're running the large 12V yellow top and a CVR 7970 alternator. Voltage stays pretty steady from start to finish and we keep it 'topped up' between rounds. With our twin turbo combination the 7805, when working, made more power than the 7531, so we'd love to continue using it.

    We live in Australia and have it already packed up ready for shipping, but thought I'd give the forum tech a go first.Thanks for your time.

  2. #2

    Default

    For that issue sir, please call us at 915-857-5200. Use ext 2255 for Pro Mag so we can troubleshoot it, and if needed get, it sent in.
    shake-n-bake

  3. #3

    Default

    Will do, thank you.

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