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Nissan CDI failure mode?

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  • Nissan CDI failure mode?

    I have an NSF-5B that was converted to 6HP with a carb. It has been running flawlessly for a year.

    Was running it over the weekend and after about 15 minutes of almost full throttle (about 5200 RPM) I noticed it miss a couple times. A few minutes later it started losing power. We were almost at the destination, so I dropped down to about 3000 and ran for another 3-4 min, then when down to just over idle as we were approaching the anchorage. Before we got there, the engine quit. It stumbled a couple times just before it quit. I tried to restart and noticed the oil lamp blinking crazy, so I thought I might actually be low on oil... as I hadn't put any in for months (didn't seem like it ever needed it). It was low on the dipstick, so I put a little in, but being careful to NOT overfill per Paul's previous guidance on here. Ran it again on the way back, but due to lake conditions didn't go as fast. As we were approaching the marina I noticed a few more misses, but it made it back to the dock ok. It was one of the hottest days we've had this year.... ~90.

    Today I took it out on the lake today (and it was hot again). I ran it back and forth for a bit and started to notice an occasional miss but also a hesitation at mid-throttle when throttling up. Took a while but it finally died. As it was dying, I was careful to observe the oil light and it DID NOT light at all. When I tried to pull-start right away, the oil light was blinking like mad, just like the day before. I popped the top and checked over everything and nothing seemed amiss. The coil and CDI were hot, but not more than you'd expect being connected to the block or 1" from the head. I had a cup handy, so I poured some lake water over both for a minute or so. Pulled the cord and it started up. Ran around again till it stopped and repeated the exercise and it started up again. The oil light was not blinking or lit before it died, but blinking when I tried to pullstart right away.

    If I was foaming the oil, wouldn't the low oil pressure light blink before the engine would die?

    Is it possible the oil pressure switch is bad? This would make sense for the blinking light when trying to start, but does not explain why it dies in the first place. I didn't think of it while I was out there, but I should have disco'd the oil switch wire and tried to start it.

    I'm wondering if it's a heat-related CDI issue, but I'm not familiar with different CDI failure modes. Is this something that anyone has seen before? However, since the oil light is blinking, I don't know how that could happen without the oil switch making contact.

    Suggestions? I do have the real service manual and can do all the resistance checks but wonder if this would show anything unless the CDI is heated to temperature. This unit has the exciter coil and pulser coils, and I can check those too (but have the same heat-related concern).

  • #2
    For a starter install a new spark plug well gaped and check OB behaviour . Don't know if a bad oil switch will account for those symptoms. When dealing with electrical components behaviors there's 3 conditions : Good, Kaputt or Intermitent, being the latter the most PITA to troubleshoot and diagnose properly.

    When cold electric components works well, when internally heated OB starts to miss, when cools down will work ok momentarily till heats up again, a never ending repetitive issue. When measured cold will be Ok, the issue is measuring them when heated up and missing while OB sits at back transom.

    Have learned that the fastest way to find the culprit is swapping new for previous electrical components which have in stock. Plan to keep my OB for a looong time, but that's me...

    Happy Boating
    Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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    • #3
      Luis is correct that troubleshooting bad electronics that are intermittent will test your patience. The oil lamp is working properly; It should be OFF when at pressure, and always blinks when pull starting, so that's OK.

      Your issue could be anything from an overheating CD to a chunk of crud in the carb to who knows. I would try running with the cowl off to get a little cooler, and see whether you still have problems. If you do, then if thinking it's electrical (pull the plug, and if wet, there's no spark), test when hot. Having a spare exciter and pulser (about $30 each MSRP) might be money well spent as these items may disappear from the shelves in future years.
      Paul
      Buffalo NY USA

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      • #4
        Originally posted by pvanv View Post
        The oil lamp is working properly; It should be OFF when at pressure, and always blinks when pull starting, so that's OK.
        That's why I elaborated a bit on the light. I do always see it blink just A LITTLE when I pull start, but when this is acting up, it is blinking A LOT when I pull start.

        I don't know if it's coincidental or not, but I had just added a tach that day. It's a KEDSUM, the kind that wraps around the coil wire to sense the spark. I have since removed it but it got me thinking... I wonder if there is some impact when you wrap that lead wire around the coil wire... it's acting as a slight choke to the spark current and if something like that could affect a CDI by adding some type of 'back EMF' into the primary side of the coil... not unlike just leaving the coil wire unplugged when you're cranking the engine.

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        • #5
          Installing induction tachs pick-up wire wrapped 2-3 turns on any of both spark plugs cable won't interfere with anything electrical or mechanical related. Just curious, are all grounds and electrical components contacts in well cleaned and shinny cond ? Seen some electrical components contacts fail due to rusty conditions which can heat up and even short any component.

          If oil amount is adequate and oil light goes off when OB has started nothing to worry about. Get a Spark Indicator (Lisle) has some nice ones and check spark strength, but will not indicate which electrical component is intermittent if that were the case..

          Do you know of anybody that will lend momentarily a CDI or a Ignition Coil to test on your OB. Pulser and Exciter Coils usually don't go bad.

          Happy Boating
          Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

          Comment


          • #6
            Originally posted by Sea Rider View Post
            Just curious, are all grounds and electrical components contacts in well cleaned and shinny cond ?
            The engine and connections are "showroom clean".

            Originally posted by Sea Rider View Post
            If oil amount is adequate and oil light goes off when OB has started nothing to worry about.
            Once running, there is no issue with the oil light. Only when attempting to restart after it has quit does this become a concern and it exhibits a different behaviour than when normally starting it.

            Originally posted by Sea Rider View Post
            Do you know of anybody that will lend momentarily a CDI or a Ignition Coil to test on your OB. Pulser and Exciter Coils usually don't go bad.
            Last year I had another motor (4A that I converted to 5HP) that I could have used as a 'parts loaner'... but I sold it! ARRGH!

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            • #7
              Sign up today
              Minimum investment, check running cond with a new spark plug gaped to specs, see what happens..

              Happy Boating
              Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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