Spark plug wires giving off blue sparks

[chitwnvw]

My bus was running a bit rough, so I pulled into a pretty dark alley to take a look, opened up the engine compartment and saw some of the spark plug wires throwing off blue sparks to various metal components. I moved the wires around a bit to stop this. The ride home was much smoother. What's causing the wires to do that?

[vwlover77]

The insulation has broken down due to age, heat, moisture exposure, etc... Time for a new set of wires! Based on my past experience, I would not recommend Bosch (now made in Mexico).

[chitwnvw]

They are Bosch with all of 100 miles on them from Bus Depot!

Any advice on a different set, maybe something I could get at AutoZone or Murray's? They always have the regular set and the premium ones, is it worth something to pay the extra 10 buck or whatever?

[vwlover77]

The brand new Bosch ones are arcing??? Wow! My new Bosch wires were arcing right at the post on the coil. The whole ignition would cut out from time to time at highway speeds as if the key had been turned off. Not fun! After that, I put the old wires back on and it ran OK.

One thing to be sure of before replacing the wires again is that your ground strap from the transmission to the body has a clean connection and is not worn out or broken. If that's the case, the spark plugs will no longer be grounded and the spark will find somewhere else to go.

I'm currently having a problem with arcing where the #1 plug wire connects to the plug with the old wires so I've ordered up a new set of "German" wires from Bus Depot that I think are made by Beru. We'll see how those work.

I'll bet the Depot would be willing to work with you if it turns out that the wires really are bad.

[chitwnvw]

One thing to be sure of before replacing the wires again is that your ground strap from the transmission to the body has a clean connection and is not worn out or broken. If that's the case, the spark plugs will no longer be grounded and the spark will find somewhere else to go.

Now that would be a weird twist to my travails.

I know the strap is there, I remember seeing it when I cleaned the tranny. I can use some sort of continuity tester on that ground strap, right? I think my voltmeter has some setting on it, where it passes a current out one probe and looks for it's return to the other probe. My electrical acumen isn't the best, but I try.

[vwlover77]

Yes, you would want to use the ohmmeter function of your meter. You are looking for zero resistance, so use the lowest range it has (like Rx1). Start by shorting the test leads together and using the adjustment knob to set it to exactly zero (full-scale on the meter). Then, put one test lead on the transmission bolt where the strap connects and the other to the other end of the strap where it bolts to the body (clean the bolt heads if needed to get a good connection). If your meter reads anything other than "zero", you've got a problem. Wiggle the strap around while you measure and look for any change (you might need a helper). It should read a solid "zero" the whole time.

[Sluggo]

Not to hijack , But what are the best wires to use now?

[vwlover77]

Not sure, but Bus Depot carries Bosch, NGK, and the "original German" which I think are Beru. I'll be able to report on the original German ones shortly as I have a set on order.

NGK has a good reputation for "Japanese quality" as a supplier to all the major Japanese brands (Toyota, Honda, etc.), but I've never used any of their products.

[Amskeptic]

Mild correction here, the ground strap does not relate to the high tension inducted current in the coil. That ground is self-contained on the engine.

Night time blue flashes are normal. They are little ghostly traces running down the wires, normally most-visible where wires contact each other.

Your best bet with new Bosch wires is to use the factory plastic clips that ensure that the wires do not touch each other at all anywhere on the engine. There is also a clip that resides at the left front corner of the breather box that holds the 1/2 wires. Both sides of the engine clip the 1/3 wires to the upper covers, have them route under the intakes on FI engines and under the central idling octopus. By cutting the wires before screwing on the spark plug connectors, you can custom tailor the loop of the wire from the cap to the clips and to the connectors so that there is NO touching of any wire with any piece of metal or adjacent wire.

[Sluggo]

I got my wires from Bus Depot a little more than a year ago. I forget the name brand but it said "made in Germany". It wasn't Bosch, Beru or NGK.

[chitwnvw]

The ones that I just took off were solid black with no markings at all. The ones I put on were the ones I got off my '79 and that had Bosch Premium or something like that all over them. So maybe the first wires weren't Bosch after all, but I did get them from Bus Depot!

It does seem to be running smoother now.

[vwlover77]

I stand corrected on the ground strap comment. Colin is right. What would be the effect of a bad ground strap? I suppose it would be a weak spark due to the coil not getting enough voltage/current to do its thing.

The Bus Depot wires I just received today came in a clear plastic bag marked "PVL" and "Made in Germany". They are all black with no markings, and look pretty basic.

I installed them today and took a very brief drive. It could be my imagination, but it seemed like the engine was running better and idling more smoothly.

[Amskeptic]

What would be the effect of a bad ground strap?

The Bus Depot wires I just received today came in a clear plastic bag marked "PVL" and "Made in Germany". It could be my imagination, but it seemed like the engine was running better and idling more smoothly.

The transaxle ground strap will show evidence of poor ground with starter. That is when the battery needs all those electrons coming homein a hurry.
Coil/choke/cut-off current is too tiny to overwhelm the ground strap without having already made itself known by giving you a no-start or lousy turn-over. The fuel injection system grounds itself through the engine which then has to ground through the transaxle strap and other more subtle paths like the clutch cable, accelerator cable, engine tin/heater valves/heater cables, anywhere where the metal of the car itself contacts the engine/transaxle.
Colin