In a message dated 21/08/01 05:25:44 GMT Daylight Time,
owner-fot-digest@autox.team.net writes:
> Date: Mon, 20 Aug 2001 16:26:49 -0600
> From: William G Rosenbach <wgrosenbach@juno.com>
> Subject: Re: Spitfire Intermittent Misfire
>
> Russ,
>
> Something to consider is the fuse that supplies the ignition. The glass
> tube type of fuse can look perfect yet pass electricity when it decides
> to, and not when the mood strikes.. This can cause no end of grief. It is
> a cheap test and worth checking first.
>
> Bill
> 70 GT-6+
>
> On Mon, 20 Aug 2001 19:31:05 +0100 Russell <rjmunns@btinternet.com>
> writes:
> > Please help
> >
> > I was Racing my Spitfire in the TSSC championship at Snetterton UK
> > yesterday when a strange misfire occurred on the green flag lap,
> > which
> > nearly caused me to miss the start. I turned the engine off an
> > re-started
> > it and the misfire cleared. I then raced without any problems at
> > all.
> >
> > I had experienced the same problem once before when running the day
> > before
> > a race. The engine was ticking over and was up to temperature, when
> > it
> > slowly died. I could not get the engine revs to increase with the
> > throttle
> > and the engine died. When I re-started the misfire had gone. I have
> > never
> > had a misfire when racing!
> >
> > Why would the engine misfire then die after ticking over, only to
> > restart
> > and run trouble free?
> >
> > The following outlines my thinking so far.
> >
> > 1: Not fuel as I would have problems during race rpm
> > 2: Not fouling plugs as the engine would not restart as easily as it
> > does
> > 3: Must be electrical because of the way it clears after restarting
> > 4: This leaves the following electrical items
> > A: Coil
> > B: Condenser
> > C: Cracked Distributor Cap
> > D: Rev Limiter malfunction
> >
> > For info, I run a 1500CC engine with points and Lucas distributor
> > and Lucas
> > Sport coil.
> >
> > Please help if you can. I think one of these will solve the problem
> > but I
> > want to understand what is happening as well.
> >
> > Russ
> > Http://www.btinternet.com/~rjmunns/
Russ,
I think you are on the right track with the ignition parts, as I have been
having an annoyingly intermittent problem with my ignition on my Vitesse
also.
(That's a pretty Herald by the way!)
I first blamed the Microdynamics F1 electronic 'black box' which incoporated
a rev-limiter, I originally bought it back in 1986, but it wasn't finally
fitted until the car was completed in 1997, so it was 11 years old when first
used.
I had the misfire, and noticed that when I bypassed the MD F1 system, it
'apparently' stopped the problem, then I put it back on and the problem
'apparently' returned. Therefore I replaced it with the excellent MSD Digital
6 system. The car then ran much better, and my fuel consumption improved by 3
miles per (UK) gallon, and the exhaust turned from black to grey.
Then the misfire returned.
I changed the battery for a higher output Optima Gel battery. Nice piece of
kit with 720 CCA.
Then the misfire returned.
I swapped out the elderly but low-mileage Microdynamics Silicon High Tension
leads for Magnecour leads, more improvement.
Then the misfire returned.
My attention turned to the Microdynamics uprated coil, (with cold-start
adaptor etc), I fitted an MSD coil of 45,000 volts output.
That seemed to help some.
Then the misfire returned.
Although the Lucas contact breaker points were fairly new with just a couple
of thousand miles on them, I renewed them, and the car wouldn't start at all.
I put the old ones back and it started fine. I then replaced the
condensor/capacitor instead, and it started OK, then I put the new points
back in again, and this time it started first time, so I deduced it was
breakdown of insulation within the condensor.
Problem solved.
Then the misfire returned.
Yes, the NGK-V type Spark Plugs were fine...
and the distributor cap, and the rotor arm.
The misfire was still raising it's ugly head. Hmmm
I decided to dump the antiquated contents of the distributor and fitted a
Pertronix/Aldon Ignitor with Hall-Effect Magnetic Triggering.
Did that.
It seemed to make an improvement.
Then the misfire returned.
blast!
sob!
grrrr!
Coming home from a show, the engine cut out. It was clearly electrical.
I stopped, it started again, on the button.
I decided that it was time that I stared real hard at the fuse box.
My car has a 12-fuse box made by Bosch and 'ceramic' fuses, (which are
actually made of plastic)!
Previously, I had a Lucas Fuse box from a Triumph Stag, (I do try to use
Triumph parts!), but I have long since removed that piece of crap, as it
caused nothing but problems from day one. (another story).
Back to the plot.
With the engine running, I loosened each fuse in turn, by poking the prong at
one end of the fuse with a pencil, and when I got to one of the blue 25 amp
fuses, and lo, would you believe it, the engine cut-out!
Now, I didn't make the otherwise perfect wiring loom/harness, I had an
automotive electrician pal make it for me, although I do have some electrical
knowledge, and know that the ignition circuit is not supposed to run through
one of the fuses in that way.
Nor do I know, for sure that the cause of my problem was a slightly loose
fuse? but it certainly looks that way!
This might have seemed obvious, (and expensive), with that most wonderful of
things, hindsight, but at least I now have a really nice ignition system.
Time, methinks to get my automotive electrician pal, to take a look at the
way the ignition is wired behind the fuse box!
and Russ, I suggest that you do just what Bill Rosenbach says, check the damn
fuse, and it's holder!
Best Regards
Lion F Guyot
1963 Triumph Vitesse 2-Litre Convertible (Diva), with ass-kickin' ignition
system.
1988 Volkswagen 1600GT Scirroco Coupe (Driver)
Wimbledon, London, England.
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