ht lead earthing / arcing out

[l1ttle_d3vil]

the sr coupe has started fouling plugs and running like a sack of sh*te recently, haven't changed anything on it. most times when started from cold it sounds like its running in 3 cylinders until it warms up. not sure if the fouling of the plugs is due to leaky injectors or weak/dodgy spark (hence not burning all the fuel, if thats possible???) one thing i have noticed though is if I unplug any one of the HT leads while the engine is running the coil will start arcing from the tip to both terminals. it will also earth out in the middle of the ht lead onto the oil dipstick!

* the coil is new.
* the ht lead from coil > dizzy is new.
* the ht leads from dizzy > plugs are a bit old (last time resistances were checked it was fine though).

why would it be earthing out like this?
* is it likely to be shot ht leads?
* could it be a dodgy earth somewhere (there is the white crap appearing on the battery)
* the ht lead from coil > dizzy is about 1mt long, is the length of it likely to effect performance to any great extent or cause the arcing?
* or could this more likely be a wiring/ecu problem?

i understand it could probably be any of 100 things but hopefully someone can give me a rough idea from the above info so any help would be appreciated.

cheers
-matt

[matt dunn]

one thing i have noticed though is if I unplug any one of the HT leads while the engine is running the coil will start arcing from the tip to both terminals. it will also earth out in the middle of the ht lead onto the oil dipstick!

If an HT lead is sparking out of anywhere except one of the ends than it is faulty.


Is the coil new new, or s/h new. Usually if it can spark from the HT tip to the low tension terminals it's buggered too, or the HT lead or HT cover on the end of the lead.

[l1ttle_d3vil]

brand new, from repco though both HT lead and coil are less than 1000km old. what would cause them to crap out so soon?

[Crampy]

Also, you shouldn't really be pulling the leads off and not giving the spark somewhere to go, it can root your coil or ignitor. Try it with a spare spark plug on the lead you removed and earth out the spark plug somewhere so it does spark.
My little Shit box Pulsar used to arch out and miss and all sorts. I had to replace the leads and the coil and ignitor, then it finally went properly.

[jondee86]

Doing it is the dark is a good way of seeing where sparks come from,
and finding out if high voltage is tracking to earth. If a spark can jump
from the lead to the dipstick, then you basically have a pinhole in the
insulation. Replace the lead with a quality piece.

Sparking on the end of the coil (a bit like miniature lightning) between
the high tension post and the casing or earth terminal is usually tracking.
Carbon deposits form a conductive layer on the surface, and when the
resistance of that path to earth becomes less than the resistance of the
plug gap, the spark takes the path of least resistance

Tracking fuses some of the carbon particles to the surface, and makes
a thin line that is difficult to remove. Moisture or condensation plus a
layer of dust is also good for promoting tracking... one of the reasons
you should always keep coils, leads, plugs and distributor caps clean
and dry. Tracking can also occur inside the dizzy cap

Cheers... jondee86

[l1ttle_d3vil]

Moisture or condensation plus a layer of dust is also good for promoting tracking...

interesting, it has been pretty cold here and i've noticed in the last month or so that everything metal in the garage is being covered with condensation (bit like the house windows in the morning). obviously that would be getting into anything, and it seems to have gotten alot worse since its got colder.

maybe it will be worth it in investing in a new dizzy cap and ht leads...damn ht leads are expensive though!

what about the length of the ht lead going from coil to dizzy though? i've had people tell me having a really long ht lead can effect performance, not sure how true this is though.

thanks.