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  • Spark Plugs

    Just recently bought a 02 4x4 bi-fuel and had it throw a spark plug in moab a couple weeks ago. was a big P.I.T.A. Anyway it got me to thinking. is there anything to do to the truck that might help prevent this from happening or is it something that just happens. i love this truck but fixing a plug blow out sucks.
    some other questions. does anyone know why it happens more to the cng vehicles?
    does it have to do with putting a stress on your engine like offroading in sand or towing heavily?

    just kinda curious about this kinda stuff. cng is to cheap in utah to just give up the truck but i want a good truck that wont leave me stranded again.

    any info would be awesome.

  • #2
    Re: Spark Plugs

    Happened to me on my van, search for the thread if you want to read more about it or go to: blownoutsparkplugs.com.

    It is a 5.4L problem as opposed to CNG.


    ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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    • #3
      Re: Spark Plugs

      As has been stated, this is a problem with the Ford 5.4 V8, not just CNG. Yours is a bi-fuel. If anything a dedicated CNG vehicle might be more prone to the problem, as those engines have a higher compression ratio than the bi-fuel vehicles. I would expect the bi-fuels would have the problem with the same frequency as gasoline only engines.

      It is well documented that this is a design problem in the head, with not enough threads engaging the spark plug. Too much force per existing threads can weaken the surrounding metal and eventually blow out the plug (actually the threads of the head and the plug).

      You asked about prevention. The prevention is either to:
      1) NOT torque the plugs beyond manufacturer's spec, or torque to the low end of the spec. An accurate torque wrench and good technique (making sure the socket is not dragging against the spark plug tube) is required to make sure they are torqued correctly. Studies have shown that under-torqueing of fasteners leads to faster failure than (slight) over-torqueing.
      As well, making sure that there is no liquid from coolant lines (or condensation from AC lines) leaking into the spark plug tubes. This will prevent possible corrosion which can exacerbate the problem.

      2) Repair all cylinders now with some sort of helicoil or thread-sert designed for the problem. This is obviously very labor intensive.
      Last edited by Black Mariah; 07-21-2010, 06:22 PM.

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      • #4
        Re: Spark Plugs

        Originally posted by Black Mariah View Post
        You asked about prevention. The prevention is either to:
        1) NOT torque the plugs beyond manufacturer's spec, or torque to the low end of the spec.
        In this particular case with the 5.4L Fords, the mfg torque spec is not enough.

        blownoutsparkplug.com recommends a spec of 28 foot pounds.

        http://www.blownoutsparkplug.com/faqs.htm

        Q/A #28.


        ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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