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How To Change a Spark Plug

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This step by step instruction will show you how to change a spark plug. It's one of the easier and basic maintenance tips for your ATV, Jeep Wrangler or other 4x4 and is really simple to do. The benefits of having good spark plugs are very noticeable in the performance of the engine.

Difficulty: Easy
Time Required: 5-10 minutes per plug

Here's How:

  1. Gather the necessary tools and replacement parts listed below, including the socket, driver, extension(s), new plugs, a gapper and some rags if the wires and/or engine is dirty or greasy.
  2. Make sure the engine has had time to cool off. The plugs will be hot for a little while after a running engine has been shut off.
  3. Remove the spark plug wire by pulling it in the same direction that the plug is pointing. The boot on the spark plug may be difficult to get off so pay attention to where your hand is going to go when it does come free. I say this from painful experience.
  4. After you ensure there is no dirt, oil or debris that can fall into the cylinder after you remove the plug, remove the plug be putting the socket wrench/driver on the plug and carefully turning it to the left, counter-clockwise.
  5. Once the plug is free, pull it straight out being careful not to bang it into anything.
  6. Make sure the new plug is set to the correct gap using your gapping tool and data you can get for that particular plug from the parts store where you buy it, in the vehicle's manual or on-line.
  7. Install the new plug, being careful not to tap the tip on the engine block because it could easily change the gap setting causing the engine to run poorly. Do not over-tighten the spark plug. If you don't have torque spec's and a torque wrench I suggest you tighten it by hand as far as you can (with or without the socket on there (without the driver!), then use the driver/handle to tighten it another 1/8th of a turn.
  8. Re-connect the spark plug wire. Wiggle it and give it a light tug to make sure it seated properly. You should be able to feel it when it gets on correctly.
  9. If you have more than one cylinder, follow steps three through eight in their entirety for all the remaining plugs. It is best to do them one at a time so you don't risk putting them back in the wrong place, which would cause the engine to misfire or not start at all.

Tips:

  1. You can sometimes tell what may be wrong with an engine by simply looking at the condition of the plugs. For example a wet, oily plugs could mean bad rings.

What You Need

  • A 3/8 or 1/2 inch socket driver
  • Extension(s) 3 and/or 6 inches
  • Socket for your plug size (usually around 1/2 to 3/4in)
  • Swivel adapter for tight spaces
  • New spark plugs
  • A spark plug gapper

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