High tension 'snap crackle and pop'
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Thread: High tension 'snap crackle and pop'

  1. #1
    Fellow Frogger!
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    Default High tension 'snap crackle and pop'

    The 2 litre 505 motor in the 404 is running quite well with it's new carby but the high tension noises from the spark plug tubes are quite consistent when the engine's at operating temperature.

    It really is a crackle and pop kind of sound and the idle is a bit uneven...it doesn't obviously miss when accelerating but it could be a lot smoother. It has a standard coil and electronic ignition ( operated without points)

    I have replaced the plug insulators and tried different connecting arrangements for the h/ t leads...original Pug 504/505 variety and japanese rubber plug varieties...still the crackle continues

    All informed advice is appreciated.

    John

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  2. #2
    COL
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    It is obviously breaking down somewhere.

    Go out and look when it is dark and you should be able to see the arcs across to the spark plug tubes, you will then know where it is breaking down.
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    1000+ Posts Beano's Avatar
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    Yes....night time is best.

    And don't forget that if you touch it, electronic ignition coils give much more of a kick than points ignition coils.

    If all else fails :
    Plug insulators come in a few different types. If you have the thin ones which screw on to the top of the plugs, buy some of that clear plastic tubing that hardware shops sell by the metre, and use it as sleeves on the outside of them, but inside the metal plug tubes.
    It will stick on very slightly due to heat, but no too much. I used some for a year once, no prob.

    At a pinch, you could always get Toyota plug leads from a wreckers. In them, the leads are sealed on very well to the plug extensions. In some models of Corolla the spark plugs are hidden down tubes like a Pug.
    They are same diameter spark plug hole but the lead length to the dizzy will be different. Measure yours and get equivalent from a couple of different Toyotas.
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    Advice from Beano is spot on!
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  5. #5
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    Thanks Beano,
    You're correct - it's the insulated plug extension devices that are the problem, New ones didn't fix it and even new Corolla style rubber seals didn't stop the crackle and pop! The Toyota seals are very good at keeping everything dry
    So we'll get some PVC tubing from the hardware store and see how that goes.
    It must be the higher power from the electronic ignition that is causes the grief.

    Cheers

    John

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    1000+ Posts Wildebeest's Avatar
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    I'm wondering [no, not wandering]. Could there be a bit more resistance in the plug leads allowing the spark to find the easy way out?
    I would change the leads for wire cored and to hell with the neighborhood TV's and radios!

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    1000+ Posts Peter Chisholm's Avatar
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    What are the plugs like and are the plug threads nice and clean?

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    At a pinch, you could always get Toyota plug leads from a wreckers. In them, the leads are sealed on very well to the plug extensions. In some models of Corolla the spark plugs are hidden down tubes like a Pug.
    They are same diameter spark plug hole but the lead length to the dizzy will be different. Measure yours and get equivalent from a couple of different Toyotas.
    Toyota plug boots shown in the image. And also a toyota ignition module used with a 505 reluctor dizzy.

    High tension 'snap crackle and pop'-ignition.jpg

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    Just a side note when we converted an old Fiat 124 to electronic ignition we kept the original coil wondering maybe your coil is too powerful for the ignition circuit?

    Sent from my GT-I9195T using aussiefrogs mobile app

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    Thanks Gents,
    It's got newish leads, brand New plugs, standard coil and Toyota seals have been used ( Until I wanted to watch as well as hear the fire works down there..when I reverted to the original 505 plastic caps.)

    Shall try the PVC cure and see how we go ? I shall report back.

    Cheers

    john

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    Quote Originally Posted by bahay View Post
    Thanks Gents,
    It's got newish leads, brand New plugs, standard coil and Toyota seals have been used ( Until I wanted to watch as well as hear the fire works down there..when I reverted to the original 505 plastic caps.)

    Shall try the PVC cure and see how we go ? I shall report back.

    Cheers

    john
    It is possibly the plug extenders. Certain XN engines has solid brass extender, try to find a set, then sleeve them with a few layer of heavy duty heat shrink tube.

    High energy ignition will always "find" the weakness in your system.

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    Lookig forward to the night time diagnosis!

    Cam
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    Quote Originally Posted by cam85 View Post
    Lookig forward to the night time diagnosis!

    Cam
    Daylight diagnoses are possible with this problem...you can Hear the racket echoing down in them toobs!

    Blind Freddy will be able to tell me

  14. #14
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    PVC tubing over the extenders did slow down the noise just a little, but it's still obviously there.

    Have looked out some of the old brass cored extenders (they are the ones that have black plastic outer shield) and applied two layers of shrink wrap as suggested by Robmac...I expect get round installing them on Friday..I think the boss has something planned for tomorrow.

    If this doesn't work I might have to go back to a points distributor...and mess about with timing, dwell, capacitors etc ?

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    1000+ Posts robmac's Avatar
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    John,

    I doubt messing around with any of the above will sort it. The problem would seem to me one of simple insulation issues.

    The optimum heat shrink is heavy duty glue impregnated type. The normal thin type won't cut the pud where HEI is involved.

    See if you can locate exactly where the leakage is happening, and don't discount oil covered spark plug insulators , or even cracks in plug ceramic tops.

  16. #16
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    Thanks Rob. Will take the plugs out and clean the insulators thoroughly, try the heat shrink shrouded brass extenders (and swap a clutch master cylinder while in the vicinity) and give it a run. The spark plug tubes are relatively clean and dry (oil free)on this cylinder head but I'm really keen to sort this bug.
    Would really like a smooth motor again ...just makes a car so much nicer to drive.

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    Heatshrink is a good insulator, but as above make sure the surfaces are clean before applying it or the spark will just run along the inside edge through all the gunk.

    PVC tube is a poor choice for the temperatures around the engine, Silicone or PTFE (teflon) tube/pipe would be a much better choice if available (try brewing suppliers or other places with food grade products) as they withstand higher temperatures.
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    Quote Originally Posted by hypermiler View Post

    PVC tube is a poor choice for the temperatures around the engine, Silicone or PTFE (teflon) tube/pipe would be a much better choice
    You're probably right. I had a think about what I said, and apart from silicone or PTFE, possibly electrical conduit would be the go. It's easily available from the hardware. There is a type that looks like bakelite, too....same as original 504 / 505 plug insulators.
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    Run your tongue along the lead whilst it's running. That should show where it's leaking pretty quick.......

    I touched one once by accident and wouldn't recommend touching one again.

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    Quote Originally Posted by Warus View Post
    Run your tongue along the lead whilst it's running. That should show where it's leaking pretty quick.......

    I touched one once by accident and wouldn't recommend touching one again.
    Yep, it's like the EHT from an old CRT TV.

  21. #21
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    Yep, it's like the EHT from an old CRT TV
    Whilst employed part time during my Uni days, I watched my boss jump around whilst being "livened up". By his gold braided necktie. which had fallen inside the EHT section of a TV he was working on.

    I did manage to turn off TV, but it took him a while to forgive me laughing at him.

    He said it felt like someone was strangling him.
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  22. #22
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    Reporting back gents!
    Cleaned plugs and insulators with brake kleen, used brass cored extenders also cleaned as above and shrunk wrapped two layers of heavy duty stuff, cleaned the cylinder head sparkplug tubes and thread with cloth wrapped long screwdriver.
    Motor starts readily, and although a little rough when cold smooths out a little when it warms up...but the crackle becomes noticeable when warmed up and is most obvious when it settles to a rough idle.
    If I rev through to say 2500rpm (in neutral) it revs well with a few carby related hiccups. It pulls fairly well when driving through the rev range with no blatant misfiring.
    If it were a standard ignition system I'd think about a dodgey condensor.. but with the electronic arrangement that's factor has gone.

    Maybe I'll try a new set of ignition leads? or failing that go back to a "points" distributor??

    John

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    Nothing wrong with a well adjusted, cleaned and matched set of points......I think I might have done a million or miles on them....
    Don't it always seem to go that you don't know what you've got 'til it's gone............

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    I think the plug lead replacement should be an interesting check.

  25. #25
    1000+ Posts Beano's Avatar
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    So you had a look at nighttime ? See the pretty sparkles ?

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