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