Malcolm Walker wrote:
>
> On Wed, 26 Nov 1997, Bob Danielson wrote:
>
> > Just had the alternator on my 75 TR6 rebuilt and, it may be coincidence, but
> > the car has started to miss. It did it a little before but rather
> > infrequently. The problem appears to be much worse when the lights and
> > heater fan are on. I've tried the plugs gapped at both .025 and .035 with no
> > improvement. It has a Lucas Sport coil and I'm wondering if it's the
> > culprit. Is there anyway to test it and if it is bad what's the best unit to
> > replace it with?
>
> I've no idea how to test a coil, but the Moss parts catalogue suggest that
> you check the low-tension lead (under the dist. cap) for signs of fraying
> or breakage. I don't know if it's on the TR6 dizzy but on the TR4 (and
> many other Lucas dist) it's a cotton-covered wire, relatively thin, that
> goes from the coil leads to the breaker points (it's cotton covered so
> that it can move back and forth with the movement of the advances without
> fatiguing)
>
> Mine is frayed and will need to be replaced. If this wire goes bad, the
> car will miss, and eventually cease to run.
>
> Just a thought...
>
> -Malcolm
One could go to a local auto parts supermarket and find a spark tester, which
(though
I've never used one), is a simple device that gives you a measured look at your
spark.
The above problem does sound like "coil" to me -- it gets worse as the coil
slowly
degrades. Just went through this with my GT6. A large draw on the electrical
system
(lights, etc.) might result in less voltage to the coil, only worsening the
symptoms.
However, a longer plug gap would definitely increase the symptoms -- although
the
difference between .025 and .035 is not that great. For a simple coil test,
take the
coil's output lead out of the distributor, and prop it (without touching) up
close to a
valve cover bolt. Crank the car. If the spark comes out skinny and yellow,
think about
a coil replacement. With a Lucas Sport, it should be fat and blue. You will
also need
to determine what caused the coil to go bad -- it should be getting 12volts in
both the
"start" and "run" keyed positions, since it is internally ballasted ...
--
Martin Secrest
73 GT6
74 Spitfire
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