collar may be stuck to the shielding barrel. Break loose the  neoprene collar by twisting the collar as though it were a nut  being unscrewed from a bolt. After the lead has been disconnected, select the proper size  deep socket for spark plug removal. Apply steady pressure  with one hand on the hinge handle, holding the socket in  alignment with the other hand. Failure to hold the socket in  correct alignment causes the socket to tilt to one side and  damage the spark plug.  [Figure 4-53] In the course of engine operation, carbon and other products  of combustion are deposited across the spark plug and  cylinder, and some carbon may even penetrate the lower  threads of the shell. As a result, a high torque is generally  required to break the spark plug loose. This factor imposes  a shearing load on the shell section of the plug. After  removing the plugs, they should be placed in a spark plug  tray.  [Figure 4-51] A visual inspection should be the first step in servicing  spark plugs. The threads on the shielding barrel and on the  shell that screws into the cylinder should be inspected for  damaged or nicked threads. Inspect the lead shielding barrel  for corrosion, nicks, and cracks. The firing end should be  checked for insulator cracks, chips, and excessive electrode  wear. The shell hex or wrench hex should be checked to see  if it is rounded off or mutilated. If the spark plug passes the  visual check, then it should be degreased using petroleum  solvent. Take care to keep solvent out of the shielding barrel.  Never soak the plugs in solvent. After drying the firing end  of the plugs, remove the lead compound deposits using a  vibrator cleaner.  [Figure 4-54]  The firing end can now be  cleaned by using an abrasive blaster. This is usually done  using a spark plug cleaner tester.  [Figure 4-55]  As the  firing end is subjected to the abrasive blast, the plug should  be rotated so all the area of the firing end is cleaned. After  the abrasive blast, the firing end gets a thorough air blast to  remove the abrasive material. The shielding barrel insulators  may be cleaned with a cotton cloth or felt swab saturated with  solvent, wood alcohol, or other approved cleaner. The firing  end should be inspected using a light and a magnifying glass.  If the plug passes the firing end visual and cleaning checks,  Figure 4-54.  Spark plug vibrator cleaner. Figure 4-52.  Improper lead removal technique. 4-33 Damage to  shielding barrel  insulator at this  point Spark Plug Reconditioning Service Figure 4-53.  Proper spark plug removal technique.