Abstract: A method of forging an article such as a camshaft, which is formed integrally with a plurality of protuberances longitudinally arranged thereof wherein a blank for the article has its protuberance-forming portions heated to temperatures higher than its other portions. The heating temperatures of the individual protuberance-forming portions are proportionate, respectively, to the radial sizes of corresponding portions of the blank to be protruded from the peripheral surface of the blank for formation of the protuberances during the compressing step.

Abstract: Forging of a camshaft which is formed integrally with plane cams arranged longitudinally thereof. A blank for the camshaft has its cam-forming portion heated to different temperatures with the heating temperature decreasing from the axially central position towards the opposite ends. Pressure is applied to the preheated blank at the opposite ends to thereby form cams on the cam-forming portion of the blank in sequence, starting first with the axially central position of the cam-forming portion towards the opposite ends. The camshaft forged using this method has a forged fibre flow with no substantial breaks and has sufficiently high mechanical strength.

Abstract: A fluid pressure passageway (14) such as a high pressure fuel line in a fuel injection system is pressurized to an upper predetermined value. Then, the passageway (14) is isolated and the length of time for the pressure to drop to a lower predetermined value is measured. The greater the degree of leakage, the shorter the measured length of time. An alarm (24) is energized when the measured length of time is shorter than a predetermined length of time.

Abstract: A sensor (16) is connected to a high pressure line (13) in a fuel injection system for an internal combustion engine. The sensor (16) produces an output current which is proportional to the pressure in the line (13). The current is converted into a corresponding voltage and a displayed a voltmeter (21). An alarm is produced when the voltage exceeds a predetermined value or range. A second voltmeter (23) is energized to display the voltage when the alarm is produced.

Abstract: A sensor (16) produces an electrical signal corresponding to the pulsating pressure in a high pressure fuel line (13) leading to a fuel injection valve (14), the pulsations being produced by opening and closing of the valve (14). The electrical signal and a reference signal are fed to a cathode ray tube display unit (18) to produce a Lissajous figure. The shape of the Lissajous figure indicates whether the Schnarren phenomenon is present and, if so, to what extent. The frequencies or amplitudes of the electrical signal and reference signal are compared to produce a signal indicating the difference therebetween which is fed to a digital display unit (22).