Club 80-90 Forums

anyone know what the resistance should be on spark plug wires? cant see anything on the lead itself -
and - any ideas on what the ohms setting should be on the multi meter?
i'm assuming you just put the multi meter leads on either end of the spark plug wires metal bits to get a reading? - and hope all 4 leads read the same?
questions questions......
will they never end?.......

Depends......most of the aftermarket leads use copper or tinned copper stranded wire inside a 7mm insulated cover..so the leads themselves have very little resistance. It's the plug caps and sometimes the connectors that carry the resistor, these are usually 5kΩ (5 Kilo-Ohm) (ends often 1kΩ) but these normally have the resistance value printed on them somewhere.

There is a possibility that you may have the much less reliable 'carbon impregnated string' type.....the resistance is in the lead itself and varies depending upon it's length....(often called 'performance' silicon but god knows why)

This HT lead typically has a resistance of 3,000 to 20,000 ohms per ft. depending on the manufacturer.

Are you dropping on to 3 cylinders? do your plug caps have shiny metal shrouds? if yes then use a pair of side cutters and remove the shrouds.

I made up my own leads using the existing ends and new lead and plug caps..this is what I used to make mine...Lucas Hypalon (quality)
http://www.ebay.co.uk/itm/7mm-HT-Igniti ... 33759b45a2" onclick="window.open(this.href);return false;

If your leads are already 'Copper core' then another option would be to just replace the plug caps themselves....I used 4 of these:

http://www.ebay.co.uk/itm/1x-NGK-Resist ... 3374f7d1f4" onclick="window.open(this.href);return false;

Martin

thanks so much for the info -
just what i needed -
suspect lead - but nothing i can see that's untoward -
can you use the lead without the shiny metal shroud?
thanks again - and really useful links

edoh wrote: can you use the lead without the shiny metal shroud?

Yes

And just to reiterate, a multimeter is of little use testing HT leads. If in doubt, just replace the whole set with new ones from Brickwerks here = Link to page

E D I T = just noticed the price of the later HT lead set at £56 = Surely that ain't right !! = Fix your old ones

Yep VW used non resistive copper HT leads with a 5K ohm resistor in the plug cap, 3K ohm if it was fitted with resistive spark plugs.

Yes indeed...after postage costs early leads particularly, work out pretty expensive.
I had the same senario just a month ago when one of my 18 month old leads decided to fail AGAIN.

The metal shrouds are there as added supression ( to minimise radio interference with TV's/Radio's to meet legislative guidelines) and before changing the leads the shrouds were routinely removed if customers complained of missfiring ( at main VW/Audi Dealerships).
So yes...they can be removed with no effect to engine running.

Like I say...I removed mine, cured the one that was breaking down (which was shorting to the head through the shroud) but ended up buying new NGK caps and replacing the actual cable on two for high grade Lucas Hypalon HT lead...just for my own piece of mind.

Martin

bigherb wrote:Yep VW used non resistive copper HT leads with a 5K ohm resistor in the plug cap, 3K ohm if it was fitted with resistive spark plugs.

Second point is worth noting......when buying plugs I make a point of NOT fitting resistor types.

Good safe reliable bet on non resistor plugs for the Wasserboxer engine are Bosch W7DC's

Martin