"Remco" <whybcuz@yahoo.com> wrote in message
news:1135557540.299326.204340@g43g2000cwa.googlegr oups.com...
> High Tech Misfit wrote:
>> Remco wrote:
>>
>> > I wonder if the problem is electrical in nature, because the RPMs were
>> > jumping around wildly.
>> >
>> > Since the tach and engine timing both get their signal from the crank
>> > sensor, I'd also look in that area.
>>
>> I thought I read on here recently that an erratic tach that precedes a
>> cut-out is a sign of a bad igniter.
>
> Not sure about any previous post on this issue, but the ignitor seems
> to just be a larger power transistor (probably a darlington, but that's
> besides a point).
>
> The way this transistor is configured, it simply acts as a switch that
> that closes/opens a contact when its input changes states (to simplify
> it all, imagine a relay with a coil and contact - that is not quite
> what a transistor is, but behaves quite similarly the way an ignitor is
> hooked up).
> When a level is applied to its input, it switches the primary side (the
> 12V side, basically) of the coil to ground and does this at a very high
> rate of speed. The secondary of the coil is what generates a high
> voltage spark.
> The output of the ignitor does not seem to attach to anything else so
> iti it breaks you won't have spark.
>
> I don't think the tach is getting its signal from the ignitor, so don't
> see how one can tell by the tach that the ignitor is bad. If you
> somehow can detect this on the tach, it must be some sort of weird
> artifact.
>
> Remco
>
Actually, I believe the tach does get its signal from a separate lead on the
igniter. The current symptoms do sound like igniter trouble, but the igniter
(and tune-up parts) are a little less than a year old... from March, IIRC. I
might be wise to re-heatsink the igniter, though.

What makes me think it isn't distributor sensor trouble is that there is no
"check engine" light, suggesting the problem is past the ECU... i.e. igniter
or coil, or high tension side (like the rotor or cap.)

Mike