PRODUCT INFORMATION
INDEX
DATE
Dep. 2
IO-G-M-33-002e F
May 2016
CONVENTIONAL SPARK PLUG REPLACEMENT CRITERIA IN
GAS ENGINES
3/3
5. USE OF THE GCS UNIT DIAGNOSIS CAPABILITY
The GCS unit displays estimated secondary voltage values (kV) for determining if the spark plugs are reaching
the end of their service life. The secondary voltage value increases as the spark plug gap increases and a
greater electrical arc is needed to generate the ignition spark.
The limit values may vary in different engines. If the values are near to 30 – 35 kV, this means that the spark
plugs must soon be changed.
If the engine is misfiring and the estimated secondary voltage value in a cylinder is very high or very low, this
may mean an ignition failure (in some cases a spark plug failure).
Fig. 2 - Secondary voltage values on the GCS unit screen.
6. USE OF EXHAUST TEMPERATURES PER CYLINDER
After a stoppage due to engine misfire, measuring the exhaust temperature of each cylinder can reveal which
one is failing. A much lower temperature than the rest of the cylinders and a much lower temperature for the
cylinder than when in normal operation means a combustion failure.
In some cases the failure is due to an ignition failure and, more specifically, to the spark plug.
This method is recommended for engines with exhaust thermocouples on each cylinder. On engines without
these, the exhaust temperature for each cylinder can be measured with a potable laser thermometer.
5.2.29
O&M_2.002211.810_A_10_2016
