Temperature and pressure activated pressure relieving spark plug

A pressure relieving spark plug for installation in a cylinder of an internal combustion engine comprising:

• a housing and a central portion,
• said central portion including an electrically conductive electrode and an electrical insulator,
• said housing including a housing wall having an outer surface and an inner surface,
• said outer surface including means for securing said housing to said cylinder,
• said inner surface of said housing wall extending around and contacting said central portion to form a pressure holding seal between said inner surface and said central portion,
• a passage through at least a portion of said spark plug, said passage having a first end and a second end, said first end of said passage terminating inside said cylinder, said second end of said passage terminating at the ambient atmosphere external to said spark plug,
• said passage being closed by at least one pressure scaling member during normal operation,
• at least a portion of said pressure scaling member becoming deformed to open said passage upon the occurrence of at least one of a plurality of predetermined abnormal engine operating conditions such that when said passage is open at least a portion of the contents of said cylinder may pass through said passage to said ambient atmosphere.