Beyond the Owner’s Manual—Spark Plugs

In this third article in our series Beyond the Owner’s Manual, we look at spark plugs, which are critical to the performance, fuel economy and emissions of natural gas-fueled generator sets. And like oil, spark plug change intervals can extend beyond what is listed in the owner’s manual. Learn how to best determine the change interval here.

Engine load, fuel quality and other factors affect plug wear. You can better determine the optimal spark plug change interval with several techniques. 

  • Trends in plug wear for your specific installation can be monitored by measuring the gap between electrodes of plugs at each service and recording the plug’s condition. Good maintenance includes regular cleaning of the electrodes.
  • Secondary transformer output reads as a percentage from the engine software or through the SCADA system, usually about 25% for new plugs. Electrodes deteriorate as a plug ages, increasing the gap and therefore the voltage needed for a spark to jump across terminals. Plug failure begins when secondary voltage exceeds 90 percent, signaling time for re-gapping or replacement.
  • A drop in exhaust port temperature in a poorly running engine indicates a plug has failed or is misfiring. If only one plug fails, it is more cost effective to replace that one plug, especially if it fails much sooner than the expected change interval. If three or more fail, it is most likely that all plugs are approaching end of life.

See us for more details on good spark plug maintenance practices.

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