[Mgs] one cylinder plug fouled

[Paul Hunt]

You've done it.  If it's oily that sounds like oil contamination is causing
the fouling and that is preventing firing.  A sooty plug that smells of fuel
usually means the plug isn't firing and that is causing the fouling.  In the
former case a new or clean plug should cause the engine to obviously run
better, with the idle changing as you pull the plug lead.  In the latter case
if it is a problem with the ignition electrics (except the plug itself) the
new plug won't make any difference to how the engine runs.  If the replaced
plug initially works as it should, but fouls with oil in as little as five
miles, you have severe oil contamination like from a badly worn valve/guide or
broken rings.  The former normally comes on gradually, the latter suddenly
Have you done a compression test?  The former should show near normal
compression pressures, the latter reduced pressures.

PaulH.

----- Original Message -----
  How do you test if one plug is not firing? I pulled the wire from one plug
  and the engine did not change. The plug seemed to be fouled black oil and
  soot.