Van runs then stops once dizzy goes black?

[jokerman]

Hi all,

Got a 2.0L Aircooled motor which requires a continuous supply of new dizzy caps.

Every couple of hundred miles the terminals inside the cap suffer oxidation where they turn black and can no longer pass the spark to the plugs.

I have changed:

Plugs, leads, coil, cap. Even fitted a new dizzy with electronic built in ignition.

Having read the last thread the next thing I'll do is check all the earths.

Just wondering if anyone has some advice as Beru dizzy caps are making a mint out of me.

Thanks

James

[California Dreamin]

Belated April fool perhaps? or Jokerman by name, Jokerman by nature?

The crusty formation on the distributor cap segments and rotor arm tip are a result of natural spark errosion and completely normal. This 'Oxidation' as you call it, offers no resistance to the spark at all. It is a common misconception that this blocks or prevents the spark, where as in reality, the worst thing you can do is to 'clean it off' by scraping it away.
Physically scraping away the 'oxidation' increases the rotor tip to segment gap which in turn takes a higher voltage to jump making the coil work far harder.
This is not an electrical contact, there are NO touching parts, so don't think of the oxidation in the traditional sense of offering a 'higher resistance' this simply is not true in this case.

The only reason to change a distributor cap is if the errosion has eaton away the brass segments OR there is evidence of spark tracking/ cap damage.

Martin

[jokerman]

So why when I clean the black deposit from the terminal does the van then run again?

[California Dreamin]

So you are saying it breaks down with is build up? is the build up sufficient enough to short out the rotor? (does it fill the air gap?)
Is this distributor original? as the only time that this type of errosion causes break down is with old fashioned contact breaker points when the condensor goes faulty and you get an unusually big spark across the points themselves.
Also....has the van got it's original coil? or a replacement? this might be the cause.
Martin

[California Dreamin]

TCI unit.......Coil.......standard electronic distributor.

[kevtherev]

The wrong coil would cause this I agree with Martin.
Does the coil get hot?