[T3] B brain

donrob at yachtsales.com donrob at yachtsales.com
Sun Jun 10 03:06:53 PDT 2018

I have seen a bad coil produce as very weak spark (especially in small 
one cylinder engines) where the engine would run, but not well.  A new 
coil fixed it right up.

I once had a beetle come in with an odd looking coil that didn't run 
right.  Replaced it with the correct Bosch unit and it ran properly.

Don Robertson
905 566-0000 (cell)
donrob at fastmail.com

On 2018-06-10 02:23, Jim Adney wrote:
> On 10 Jun 2018 at 0:31, Dave Hall wrote:
>> Why would he only see a small spark? Doesn't that suggest a ignition 
>> problem?
> I wondered about that, too, but it's really hard to know what to
> expect when looking at what a spark looks like out in the air. I
> remember being disappointed when I first did this test, many years
> ago. Since then, I've come to understand that the spark color depends
> on what's in the air, and the perceived intensity depends on your
> expectations and the gap.
> For me, the only real test is to use a timing light with an inductive
> pickup. If that triggers, it means that something jumped the gap, and
> that's enough. It's binary, there's either a spark on no spark,
> there's nothing in between.
> That's not to say that there can't be a difference between sparks
> produced by different systems, but with a given system, there's
> either a spark, or no spark. For example, I do a lot of repairs on
> Delta Mark 10 Capacitive Discharge Ignitions. With a flip of a switch
> on my tabletop test setup I can change from CDI to standard Kettering
> ignition. I can hear a difference, I can see a difference on an
> oscilloscope, I can even see a small difference in the spark, but
> when I'm testing, there's either a spark or no spark. I never get a
> "weak" spark that needs my attention to make it better.
> Well, maybe I should qualify that a bit: There are certainly times
> when some part is failing and we get a spark sometimes and no spark
> sometimes. That's what we call a "miss", and it can be difficult to
> track down the cause.

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