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  1. #1
    Join Date
    Nov 2016

    Default Tech tip - R&R spark plugs

    I'm sure we have all replaced spark plugs, but perhaps you might be able to improve your methods, and your results. Nothing I will present here was 'invented' by me, it's just stuff I picked up over the years. My 98 jeep gc was misfiring since the onset of the cold weather. Not only is this embarrassing at work, it's a pita in general. Time to pull it into the shop and fix this thing, now.

    First things first - what's needed:
    a) spark plugs, I like Champs (RC12LYC) for Jeeps, AMC's & MOPARs, but you can use anybody's plugs, just get the right plug for the engine
    b) plug wrench set up (I use a Snap-On spark plug socket/extension combo, & ratchet, I've had them for 30-40 years.)
    c) gap gauge - I use a wire gauge (force of habit). I have all kinds of gap tools, some are better than others. I use them for volume work, but I still check with a wire gauge.
    d) anti seize (some folks prefer heat transfer compound, more on this later)
    e) shop vac (very important!)
    f) silicone lube (I like aerosol, but any liquid silicone will work - DO NOT USE GRAPHITE BASED LUBE - more on this later)
    g) spark plug install tool
    h) spark plug boot removal tool

    What to do:
    a) Use a plug boot removal tool (your hand works, but I like my boot grabber) to remove the boot, A gentle twist to break the boot loose from the plug's ceramic insulator is strongly recommended before pulling the wire & boot assembly from the plug.
    b) Get the shop vac, and vacuum the area around the plug - get all that grit, rust flakes, sand and other engine killing junk out of the area BEFORE you remove the plug. You do not want that junk falling into the cylinder. (I use a piece of 1/2 inch conduit shove into the end of the shop vac hose. Seems to be about the right size to get into the recess while fitting over the plug end.
    c) Use your plug wrench set up to remove the plug. (Lefty Loosey) If the plug's been in there for a while &/or the last mechanic didn't lube the threads, you may end up with bloody knuckles (now would be a good time to wear those trendy mechanic's gloves). If the plug fought coming out, vac again just in case you knocked something loose in the plug recess.
    d) Prep the plug. Set the gap. DO NOT use the wire gauge to pry open the gap, or a hammer to close the gap. Use the gap wrench that came with the gauge. Now use apply some anti seize - be careful, just get it on the threads. If it gets on the ceramic insulator, use a little rubbing alcohol and a Q tip to wipe it off the ceramic. Make sure you get it all & get it clean. Some anti seize is conductive. That means it can cause a short circuit across the insulator. That will give you a misfire under stress.
    e) I have fat fingers so I use a tool to hold the plug when screwing it into the hole. The best tool I have found is an old straight plug boot with a large shaft screwdriver handle inserted in the wire side of the boot (3/8" drive 6" extension works great too). Screw the plug in until snug.
    f) Prep the plug wire boot before installation with a little spritz of silicone lube. It will keep the boot from sticking on the ceramic and it makes the plug wire metal connector slip on the plug electrode stud easier. DO NOT USE GRAPHITE BASE LUBRICANTS. The graphite is conductive and will cause a short circuit on the plug insulator. This will result in a misfire under load.

    Are the extra steps necessary? It seems to me that the extra time spent in prep substantially reduces the likelihood of a 'comeback' or failure down the line. Take pride in your work, do it like a 'pro'. Also, after all that work, don't forget your air filter. I've included a photo of what I thought was an OK filter till I put a new one next to it.
    Attached Thumbnails Attached Thumbnails shop vac spark plug hole.jpg   spark plug prep.jpg  

    spark plug install tool.jpg   spark plug boot prep.jpg  

    air filter comparison.jpg  

  2. #2
    abebehrmann's Avatar
    abebehrmann is offline Level: Uber Jeep Cherokee Trailer Queen
    Join Date
    May 2013
    Dallas, TX

    Default Re: Tech tip - R&R spark plugs

    Good info. Reminds me I still need to buy a shop vac so my wife doesn't get angry with me when I bring the carpet vacuum out to the garage...

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