msecres@ibm.net wrote:
>
> 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
My wife got me a spark tester one Xmas that was about $8 that looks
somewhat like a compass but with a crossbar on each leg.You stick one
end in the plug wire and ground the other one.At this point the
crossbars touch in the middle so the thing looks like an A. With the
engine running you gradually open the legs (no rude comments please)
until the gap is too wide for the spark to jump. You can then get a
reading off a scale as to the efficiency of the system.(I did get other
stuff too).Stu
|