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I have a misfire on cylinder 1 unyet i have 4 great sparks with ignition timing and valve timing checked.

I'm clutching at straws i know, but is it possible to have a long reaching spark bridging 20mm or so but still not be suitable for ignition? Or to put it another way - is it possible to have ample voltage in the 1000's of volts but somehow not have enough amps for ignition?

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  • Do all of the spark plugs look the same as far as burn pattern? How do you know it is cylinder 1 which is misfiring? Nov 30, 2023 at 13:30
  • @Paulster2 no, the spark plug in cylinder 1 is blacker i'm guessing as a result of the misfire. The blackened piston face was covered in black gunk that was quite sticky as opposed to dry powdery carbon. I know it was cylinder 1 by doing the power drop test. Removing plug lead 1 made very little difference to the engine revs. Please watch this space as I've just found something odd around valve seat of inlet valve for cylinder 1 only Nov 30, 2023 at 15:03
  • If you'd like to test HandyHowie's theory, move the #1 spark plug to a different cylinder and check to see if the problem moves with the sparkplug or stays in place. Nov 30, 2023 at 15:36
  • @Pᴀᴜʟsᴛᴇʀ2 I wasn’t suggesting it is a faulty spark plug, it could easily be a faulty lead or a faulty coil. I was just saying that a healthy looking spark outside of the cylinder doesn’t necessarily mean it will be good inside the engine. The spark may find somewhere easier to form.
    – HandyHowie
    Dec 1, 2023 at 8:37
  • @HandyHowie - I get you. The first step in diagnosing it (in my book) is to move components to see if the problem follows. Dec 1, 2023 at 9:51

1 Answer 1

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Inside the cylinder is quite a hostile environment. What looks like a strong looking spark at atmospheric pressure outside of the cylinder can become nothing at high pressures in a fuel rich environment during the compression stroke inside a cylinder.

So Yes, it is possible to have a good looking spark but but still not suitable for ignition. This is especially true if the electricity finds a much easier place to arc away from the spark plug.

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  • @handiehowie thanks for your answer. Can i ask? Have you ever had 4 great looking sparks with a misfire and then switched out the coil and all came good? Dec 1, 2023 at 11:29
  • I can’t remember, really. Does the engine have a single coil, a coil pack, or separate coils? Does it have HT leads? Have you looked in the dark to see if there is arcing somewhere on the leads or coil?
    – HandyHowie
    Dec 1, 2023 at 18:23
  • @handiehowie it has a single coil. Good point - no, i never looked for arcing in the dark. Head will be going back together soon. Thanks. M Dec 1, 2023 at 18:28

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