[T3] some problems back, some gone...

Jim Adney jadney at vwtype3.org
Sun Jun 6 13:04:24 PDT 2021

On 6 Jun 2021 at 11:32, Max Welton wrote:

> Also. some interesting thoughts from Fred Winterburn in this thread.
> https://www.mgexp.com/forum/mgb-and-gt-forum.1/interesting-ignition-failure-with-heathkit.3510763/

That's an interesting thread, with both good and poor followup posts. I 
particularly liked someone's observation that the standard Kettering ignition 
stores the spark energy in the magnetic field of the coil while the CDI stores 
it in a capacitor.

Here are a few things to consider if you're interested in adding a CDI to your 
car. These things would have been useful in that MG thread.

CDIs work best with a standard ratio coil. Performance with a hi voltage 
(high ratio) coil will actually be worse than with a standard coil.  

The Delta Mark 10B is a great CDI unit, but its built in switch is its weak spot. 
They worked well for a couple decades, but as they got older the contacts 
got tarnished and don't always maintain good contact. I have these on all my 
old VWs, so I make a habit of exercising the switches any time I'm near 
them. They don't fail on me as long as I remember to do this.

Keith's problem may also be in his switch. Keith, any chance that you're 
using one of those little Alco 4PDT toggle switches? A full size switch might 
do better in this application.  

The original Delta Mark 10 units do not have a switch, so they do not have 
this weakness, but they also lack some 10B features that may be useful, like 
hotter spark when cranking.  

The Delta literature recommends regapping the spark plugs to .040". This 
worked just fine for me until I tried to start my square in damp weather. 
Under those conditions, the extra hot CDI spark found lots of alternate paths 
to ground, before it got to the spark plugs. I've stuck with std. .028" gap 
plugs ever since. That works just fine.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

More information about the type3-vwtype3.org mailing list