Broken insulators are caused by excessive heat or pre-ignition, ping. These
conditions can be caused by over advanced timing, lean fuel mixture, or
excess carbon causing increased compression. Unbalanced/worn injectors or
small vacuum leaks can cause some cylinders to run lean. In addition to the
compression check, do a leak down test. better indication of actual
condition. Check injector seals and manifold boots. Carbon build up on
intake valves can also cause mixture imbalance.

Good luck,
Dennis

  -----Original Message-----
  From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf Of
Frank Condelli
  Sent: Friday, August 10, 2001 6:32 AM
  To: vanagon@GERRY.VANAGON.COM
  Subject: Spark Plug Failure

       Here is an item for everyones interest.  My '87 Westy has been
running
  crappy for the last few days and seemed to be getting worse.  Backfiring
  through the exhaust had me thinking burnt valve.  Yesterday I took the
time
  to start digging and find out what was going on.  Looked first at the
  distributor cap to find it full of dirt and the carbon seized up in its
hole.
   Cleaned the cap, rotor and inners, then stretched the carbon spring and
put
  the cap back in place and started up the engine.  Seemed better but still
  popping through the exhaust.
        Removed spark plugs to have a look see and found plugs at # 2 and #
3
  cylinders had cracked and missing porcelain.  What's that all about ?  The
  colour of the plugs were good and these plugs Bosch WR7DTC's were put in
  22,400 km ago !  STRANGE !  Anyways, I took a compression reading while I
had
  the plugs out and found #1 - 125 lbs, #2 - 140 lbs, #3 - 120 lbs, #4 - 135
  lbs.  Not perfect but acceptable for an engine with 350,000 km on the
clock
  and original engine.  Put new Bosch WR7DTC's in and stated up the engine
and
  VOILA !  Running great again !
             Found my oxy sensor not working in the process so unpluged it
and
  the engine seems to run fine with it unplugged. But, stumbles at idle with
it
  plugged in.  Will order up a new one.  The one that's in there now is the
  generic one from The Bus Depot put in 47,003 km ago.

  Cheers

  Frank Condelli
  Almonte, Ontario, Canada
  BusFusion a VW Camper event in Almonte, June 7-10
  '87 Westy & Lionel Trains
  Member: Vanagon List, LiMBO, IWCCC & Capital City VW Club
  Vanagon/Vanagon Westfalia Service in the Ottawa Valley
  STEBRO/Vanagon Stainless Steel Mufflers
  Frank Condelli & Associates or http://frankcondelli.com

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