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Guest Message by DevFuse

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Correct plug wire routing

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6 replies to this topic

#1 Hudmud


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Posted 12 February 2004 - 09:00 AM

In an attempt to further eliminate an easy solution to my 84 GL's surging/hesitation problem, I am replacing the plug wires today and I am curious to know if there is a correct wire routing procedure that should be followed to address the following concerns.

"Crossed Wires: You may see guides on your car that have the plug wires crossed over each other, rather than in nice parallel lines. This is intentional to cancel out magnetic fields. Wires in parallel may cause one wire to induce a voltage in another wire, causing it to fire when it shouldn't ." "Some manufactures criss-cross wires on long runs to cancel out magnetic fields which would otherwise induce voltage from one wire into another and cause mis-firing. "

I realize that there are no "long runs" like one finds with a V8 but I just wanted to check. There are 2 sets of wire clips for the #2 and 4 cylinders that wind around the alt and does it matter which wire goes where? Can a problem be potentially created if a plug wire is too close to the alt or it's wiring? Any recommendations for running the #1 & 3 wires as well as the coil wire?

#2 WJM



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Posted 12 February 2004 - 10:28 AM

hm, this is a most interesting theory...

#3 MaroonDuneDoom


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Posted 12 February 2004 - 11:25 AM

i'll reply too. lets get some attention to this one.
i've been thinking a tad bit about wires lately.

#4 SubSandRail


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Posted 12 February 2004 - 12:20 PM

Electric field density decreases logarithmically with distance. That means that if you double the distance beween the wires, you cut any transfer of power by a factor of four. Triple the distance decreases power transfer by a factor of nine. So if you like to have a nice neat wire harness but reduce the risk of firing the wrong plug, get wire spacers that have good seperation between wires.

The idea of crossing wires works, but does not "cancel out magnetic fields". It distributes the magnetic field more evenly across the other three wires, so instead of transferring power through the magnetic field to only one wire, possible causing it to fire the plug, you spread out the power, and each of the three wires has 1/3 the power, not enough to fire any of the plugs.

Also, wires in parallel are good at picking up currents from magnetic fields, but perpendicular wires are not capable of efficient power transfer. So if you route each wire at a different angle, you reduce your risk.

Field theory in a nutshell.

Also, if anyone disagrees with the first sentence, you may be confusing field density with field strength. Field strength decreases linearly with distance.

Run the engine at night, with all lights of. Open the hood and look for arcing from the wires to chassis ground. That would rob power.

#5 GeneralDisorder


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Posted 12 February 2004 - 01:24 PM

If you have a decent wire set, this isn't generally a problem on the older soobs. I wouldn't worry about it at all. The voltages that we operate at aren't enough to arc across a decent wire set.


#6 Hudmud


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Posted 12 February 2004 - 02:12 PM

Thanks for the info. Didn't think there was going to be a problem but it didn't hurt me to ask and I even learned som thin!

#7 SubSandRail


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Posted 12 February 2004 - 04:57 PM

Running it with the lights off tests to see if your wire set is good. If it is old and cracked, and is routed close to the engine block, you could get arcing.

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