The aim of the given research is improvement of the quality of the spark plugs' manufacturing technological process and of their operating properties at different stages of their life cycle. The article is devoted to control of the spark plugs' life cycle through development of a decision support system for the quality of the production process. It demonstrates the correlations between the different stages of the life cycle and spark plugs' manufacturing quality with a view to improve the technological processes, and also identifies the spark plugs' controllable and uncontrollable parameters, affecting the engine unit ignition and starting quality. The article describes an approach to development of a decision support system for the spark plugs' life cycle and certain elements of the system, implemented in real production. The described stages of development of the quality control system for spark plugs' manufacturing technological process and different life cycle stages establish a feedback between the testing and operating steps, and the steps of the product engineering and manufacturing. Within this system certain elements of a subsystem for diagnostics and decision-making were described, and for this purpose an analysis of the faults, defects and reject sources was done. The proposed system structure allows us to solve the problems of the products' parametrical identification at the designing stage and to reveal the problems, which arise during the technological operations. The described approach permits to control the quality of products (sparkplugs) at different stages of the technological process, which makes it possible to reduce the designing and manufacturing costs and to increase the products' quality and competitiveness.