Coil pack

  • 2 POSTS
  • 2.0L
  • 4 CYL
  • FWD
  • 134,000 MILES

I bought brand new spark plug wires 8.5 mm. When my mechanic put them on and I started the car and the car would not start. He put the old wires back on and the starts right up. My mechanic thinks the coil pack cannot handle the wires. Do you know what kind of coil pack I could get to handle the wires?

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have the same problem?
Thursday, November 10th, 2016 AT 7:01 PM

1 Reply

  • 29,775 POSTS

I have never heard such an excuse. The first concern is supplying your own parts. That is like bringing your own groceries to a restaurant and asking them to cook it for you. There is no such thing related to an ignition coil about being able to handle the spark plug wires. That would be like saying a water pump cannot handle the pipes. I suspect what he meant was the coils cannot develop enough extra voltage to overcome the resistance in the new wires. Spark plug wires do not actually have metal wire in them. They use string impregnated with carbon. That carbon conducts the electrical current, but very poorly compared to most metals. That has been done since the 1960's to greatly reduce radio noise interference. If your new wires were longer than the originals, they will have higher resistance. (Think of resistance as standing on a garden hose and partially blocking it). The more people who stand on the hose, the less water can flow through it. Eventually the little trickle of water that gets through does not have enough pressure to do any usable work. With additional resistance in a spark plug wire, enough voltage can be lost in that resistance that there is not enough left to jump the gap in the spark plug.

When an ignition coil develops a problem, typically internal arcing takes place or some of the loops of wire short together. Neither of those will go on for very long before a total failure occurs. Therefore, it is highly doubtful you have a bad coil. What you can try is replacing just one spark plug wire at a time. Keep in mind that when you have a coil pack, each coil fires two spark plugs at the same time, so if you have one bad plug wire, two spark plugs will not fire. If you replace just one wire and the engine starts and runs normally, you know that one new wire is okay. Replace its mate and try again. If the engine does not start now, or runs poorly, put the first original wire back on and try again. If it runs okay with only the second new wire but not with both the first and second one, the total resistance of the two together is too high and you need to find wires that are closer to the original ones.

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Thursday, November 10th, 2016 AT 8:10 PM

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