Re: [T3] When electronic points die they can still kinda work.

["Dave Hall" <dave@hallvw.clara.co.uk>]

I had that happen with the Beetle - it idled, but with foot on the accelerator,
it revved up, slowed down, revved up, slowed down.  Foot off, it idled as
before.  Very weird, but I found the wire to the breaker plate had broken,
exactly as you mention.

Dave.
UK VW Type 3 & 4 Club
http://www.hallvw.clara.co.uk/
------
----- Original Message ----- 
From: "Jim Adney" <jadney@vwtype3.org>
To: <type3@vwtype3.org>
Sent: Tuesday, August 15, 2006 3:09 PM
Subject: Re: [T3] When electronic points die they can still kinda work.


> On 14 Aug 2006 at 9:49, Toby -- '72 Squareback wrote:
>
> > What *completely baffled* me was that the engine would run fine as long as
> > the gas pedal was pressed, even if by the slightest amount.  Anyway, just
> > another bit of something to throw into people's knowledge bucket.
>
> After thinking about this for a couple days, I think I have an explanation.
>
> The Pertronics rides on the breaker plate, the same as the points did. The
> vacuum advance works by rotating this plate to change the relationship between
> the pickup and the cam. When the Pertronics moves with the plate, the 2 wires
> leading to it have to move also, so they need some extra length in there for
> the wire to flex.
>
> I suspect that after a few years of flexing, one of your wires finally broke
> inside the insulation. Of course this shut down your ignition, but when you
> moved the gas pedal, you changed the vacuum conditions on the vacuum advance,
> moving the breaker plate just a little bit. This probably flexed the wire
again
> in a way which renewed the contact and allowed the ignition to kick in again.
> When this happened, the raw fuel from the previous unsparked strokes was
> ignited in the exhaust system, creating the backfire.
>
> Alternatively, the wire may not have broken, instead, the coil wire could have
> abraded against something, worn thru the insulation,and shorted to ground.
> Moving the breaker plate could have removed the short.
>
> Either way, the fault is most likely with the wiring rather than the
Pertronics
> innards themselves.
>
> The good news is that this means the Pertronics is probably fixable, but you
> will want to repair the wire and route it to allow gentle flex, minimizing the
> chance of this happening again.
>
> You can find the break by just pulling on the wire and seeing where it
> stretches.
>
> I thought of this because this once happened to me with a set of standard
> points. I have a number of CDI ignitions which I use with standard points. One
> of the advantages of the CDI systems is that the points themselves last
> forever, but the WIRES don't! I had one of those internal wire breaks many
> years ago, and it had these same symptoms.
>
> One of the advantages of the Bosch points system our cars use is that you get
a
> new wire with each set of points. I've known people with other kinds of cars
> where that little wire is part of the distributor and does not get changed. A
> break there is more likely to eventually happen and harder to fix when it
does.
>
> -- 
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> USA
>
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