Plug wires arching, wth? Alternator charging...

[K85 Octane]

I've never seen a plug wire arch from the plug boot, but my 2001 s10 is doing this. #5 is arching from the spark plug boot to the manifold heat shield. What could be causing this? The plugs and wires are 45,000 miles old. Oddly enough, this only happens (to my knowledge) at idle or just off idle. It stumbles around 700rpm but never does it again.

Second question. My battery tests at 12.5v. With the engine hot and running, straight off the alternator I'm only getting 13.8v. Is this cause for concern? Normally I seen 14.4v but if I can limp this alternator along to save cash, I will. The alt is from a fullsize truck, 140amp, Delco (made in mexico).

 

[dhcomp]

I've never seen a plug wire arch from the plug boot, but my 2001 s10 is doing this. #5 is arching from the spark plug boot to the manifold heat shield. What could be causing this? The plugs and wires are 45,000 miles old. Oddly enough, this only happens (to my knowledge) at idle or just off idle. It stumbles around 700rpm but never does it again.

Second question. My battery tests at 12.5v. With the engine hot and running, straight off the alternator I'm only getting 13.8v. Is this cause for concern? Normally I seen 14.4v but if I can limp this alternator along to save cash, I will. The alt is from a fullsize truck, 140amp, Delco (made in mexico).

If its arcing, the boot is clearly cracked or broken. Sounds like time for wires.

13.8 seems low, but if thats the situation you're in, i'd limp it for a while. Just keep an eye on your voltage gauge, and you should be able to tell when its actually dying before it goes out.

 

[diesel4me]

If the battery is fully charged,it wont put out more than 13.8 volts ,thats all it needs to maintain its full charge...to test "total" output you need to put a carbon pile load on the altenator,you can turn all the lights and acessories on to do a crude test to see if the regulator increases the output or at least maintains it.........................................................................................The plug wire arcing is probably just due to age and heat,but sometimes spark will rather take the path of least resistance,rather than fire the plug,so any crack in the boot,the spark plug porcelain or some condition in the cylinder like excessively lean or rich mixture,fouled plug,etc, can cause the spark to jump elswhere other than at the plug's electrodes....

 

[4xcrazy]

I had a problem with this about 2 years ago, not really sure what was causing it, other than maybe a bad batch of plug wires/materials, or maybe bad spark plugs getting too hot or something, wearing down, breaking down the boot, but after about 2 days of driving, the new boots would start to arc through again onto my manifolds.

I ended up picking up dome of those kevlar boot shields and it seemed to help. Really to this day don't know what had cause it, especially since it was only on the same two spark plugs.

 

[TheBeast_88K5]

Sounds like micro-cracks in the wires, to me...

 

[4xcrazy]

Micro cracks in the wires or boots would do it, like I said, maybe a bad batch of materials or they are trying to go with cheaper materials or something, I swapped out several sets with brand new ones, still the same result, a few days later and it was arcing again. Was annoying because mine would do it all the time, lose power while driving, it was a flat out constant arc.

I replaced the plugs, thinking maybe the electrode was cracked or broken somehow inside the ceramic maing them get hotter than they were designed to, honestly, it's been far enough back I don't really remember if that fix my problem or not.

 

[K85 Octane]

hmmm Will have to check the alternator with all the accessories when I get home from work.

The missfire (or non-fire) has gotten worse. Funny how that happened. I could barely tell something was a miss 2 days ago, now it stumbles all the time at idle. It's still the wire, I can hear it and see it. Will stumble off idle, then clear up.

What a pisser to have spark plug wires (ac delco) not outlast the original wires that were one the damn thing. Remind Don't have time or desire to deal with a small engine compartment. Just going to get reamed from a shop and be done. POS$#^&^$##@#@!#%^**(^$

 

[80' 427]

Better do the plugs too I am betting it is carbon tracked.

 

[Fordum]

If the fire is arcing through the boot or wire insulation, that wire is hosed. Once it breaks through the first time, it leaves a hole and some carbon and will do it over an over.
But, change the plug when you change the wire.
When the power to the coil is interrupted, the magnetic field begins to collapse through the windings.
The voltage begins to build up.
It will continue to get higher and higher until it overcomes the weakest insulation to ground and arcs across.
That weakest point is supposed to be the air between the center and side electrodes of the plug.
If the gap is bigger than it should be, or there is something blocking voltage in the plug, the voltage will get higher and higher until either the core saturates, the field finishes collapsing, or it arcs through somewhere else.

Also, carbon tracking or cracks in the plug insulation can cause it to arc until it damages the boot.

Given the price of wires these days, its better to be safe and change the plug than risk damaging a new wire.

Also, voltage from a coil will usually drop as RPM increases, so that is probably why it only arced at idle at first.