I have replaced spark plugs for my 2005 vw fox. I noticed that in one cylinder I can see a small spark coming from the spark boot. It only appears on one spark wire.

Do you guys know if this is important issue? Also the wires are quite new and I haven't noticed any cracks or deformations on wire gum part.

  • Want to help, but not quite understanding your description. It might be due to improper terminology. Can you please clarify what you mean by "metallic spark wire head"? Are you referring to the electrodes on the tip of the spark plug? What is the "wire gum part"? Do you mean the spark plug boot? If you are unsure, put a link to a picture of what you are describing.
    – CharlieRB
    Nov 14 '17 at 21:12
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    If your wires look like these, they have to be pulled off with a special tool, and if they are not it is super easy to damage them. Half the time on my VW, the boots would get stuck so tight that not damaging them was very hard even with the tool. @CharlieRB, look at that link for a possible pic of the metallic part OP refers to.
    – JPhi1618
    Nov 14 '17 at 21:19
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    Yes, they look exactly like these that you have sent. And yes I took them out with hands as I didn't have that removal tool...
    – Mantelijo
    Nov 14 '17 at 21:24
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    Well, like I said, damaging them by pulling is easy to do. The tool you want looks like this. The tool also helps with installation, so get one now when you get the new plug wires.
    – JPhi1618
    Nov 14 '17 at 21:30

Visible sparks are not ok. I'm not familiar with your particular plug wires, but that normally means the insulation or wire connector is damaged.

If you see a spark, at a minimum it means that you're not getting a full spark on the actual plug because you're losing energy. It can also lead to premature failure of your coils because they are now trying to drive a spark through something that doesn't have the correct resistance.

Pull off the offending plug wire and, if possible, look for a tear or damaged connector. If you don't see anything, you might try to reseat the wire, and make sure it is positively connected to the plug and try again. It could just have a poor connection (not snapped all the way on).

You're probably looking at replacing the plug wires, and they normally only come in a complete set.

  • 3
    I would also note that a cracked plug could cause the spark to jump to the cylinder wall - especially if the grounding is not very good. It's unlikely that it'd be a damaged plug, but it would be the second thing to check (I think). Nov 14 '17 at 21:28
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    If you see any spark, this is electrical leakage in the ignition system ... no good at all. Agree with your analysis here. Nov 15 '17 at 0:56

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