It was only one test that showed up the 16V reading, subsequent tests have
all shown 14.x V. I will undertake some investigations...
Saskia was running superbly last night, and this morning, very free revving
with lots of power, although towards the end of my 50 minute commute the
loss of power at 3-4000revs happened again. The engine was slightly warmer
than usual after having been stationary in traffic for a while, but not
much. I have also been experiencing a few problems with the choke, it has
re-adjusted itself so that when fully in the car will tick over at about
650rpm, wheras it should be 750rpm. This means that I sometimes have to
have the choke pulled out slightly. Could this be a cause of the symptoms?
cheers all for listening,
John & Saskia
----- Original Message -----
From: "eyp_jl" <eyp_jl@netzero.net>
To: "John Hobson" <goalie_john@yahoo.co.uk>
Cc: <spitfires@autox.team.net>
Sent: Tuesday, November 28, 2000 6:57 PM
Subject: Re: warning light and alternator
> It is easy to replace the coil but I suspect the voltage regulator,
probably
> a zener diode, is getting loose (bad solder connection since the problem
is
> intermittent) and should be fixed first. If the voltage is too high then
the
> secondary/high voltage will be higher also and may be breaking down the
> insulation and shorting to ground causing the hi - rev miss.This could be
at
> the coil, the HT wire to the Distributor, thedistributor cap, the HT wires
> to the plugs or the plugs themselves. Fix the over voltage problem first
> then worry about the coil if you still have problems.
> ----- Original Message -----
> From: "John Hobson" <goalie_john@yahoo.co.uk>
> To: "Richard B Gosling" <Gosling_Richard_B@perkins.com>; "spitfires"
> <spitfires@autox.team.net>
> Sent: Tuesday, November 28, 2000 8:09 AM
> Subject: Re: warning light and alternator
>
>
> >
> > Is a new ignition coil easy to fit (in comparison to fitting my
> alternator,
> > which was simple)? Is there any way to test wether the current one is
> shot?
> >
> > cheers
> > John
> > ----- Original Message -----
> > From: "Richard B Gosling" <Gosling_Richard_B@perkins.com>
> > To: "goalie_john" <goalie_john@yahoo.co.uk>; "spitfires"
> > <spitfires@autox.team.net>
> > Sent: Tuesday, November 28, 2000 3:38 PM
> > Subject: Re: warning light and alternator
> >
> >
> > > John,
> > >
> > > I would agree that 16.9V sounds too much. The cause of this is almost
> > > certainly the alternator - this is all the more likely because you
took
> a
> > > working, used one, rather than a reconditioned (i.e. good-as-new)
item.
> > If I
> > > understand it right, the alternator generates voltage proportional to
> the
> > > speed of the engine; it is then corrected to the desired output by
some
> > > electronics in the back of it, which also converts the electicity
> > generated
> > > from AC to DC. If you are generating that high a voltage, I would
> > suspect the
> > > electronics in the back of your alternator are dodgy. It will work,
> but
> > it
> > > will damage components due to overheating over time. I'm also not
sure
> > what
> > > the effect will be on your battery of having that high a voltage
across
> > it for
> > > a sustained period - it might overheat the battery. Have a feel of
the
> > > battery casing after a long run.
> > >
> > > As for the coil, this is a cylindrical thing that is bolted onto the
> > bulkhead
> > > near the battery, with a connection at each side of the end, and one
> from
> > the
> > > middle of the end. This generates the very high voltage needed to
make
> a
> > > spark in your spark plugs. There are actually two coils inside it.
> The
> > first
> > > is connected to the live supply from the battery. It is then
earthed,
> > via a
> > > switch in the distributor. The coil has electricity passing through
> it,
> > which
> > > builds a large magnetic field within the coil. At the crucial
moment,
> > the
> > > distributor opens the switch to earth, so no more current can pass;
the
> > > magnetic field immediately collapses. This sudden change in magnetic
> > field
> > > strength creates a current in the second winding, with a very much
> higher
> > > voltage. The current is very low, but that's OK. The current flows
> > along the
> > > HT (high tension, which actually means high voltage) lead to the top
of
> > the
> > > distributor, which sends it to one of the spark plugs, and this
current
> > leaps
> > > across the spark plug gap to cause the spark. The distributor then
> > > re-connects the LT (low tension, i.e. low voltage) side of the coil,
to
> > build
> > > the magnetic field once more.
> > >
> > > This can cause poor running at high revs because, if the first winding
> is
> > > dodgy, it may not have time to build much of a magnetic field at high
> > revs
> > > (the faster the engine, the less time there is between sparks).
There
> > will
> > > therefore not be much of a current generated in the HT circuit, so
the
> > spark
> > > at the plug will be weak. However, this is but one of a number of
> causes
> > of
> > > poor high speed running - timing out, centrifugal advance on the
> > distributor
> > > (which makes the spark earlier at high speeds, to give the petrol
more
> > time to
> > > burn) not working, partial fuel blockage, weak fuel pump, mixture
> > incorrectly
> > > set on carbs for starters. My instinct is that electical drain is
not
> > the
> > > most likely cause of your high speed running problem, but is
competely
> > > separate, or is simply paranoia as you said!
> > >
> > > Well, that may be more than you wanted to know about coils, but you
did
> > ask!
> > >
> > > Richard and Daffy
> >
> >
> > __________________________________________________
> >
>
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