Abstract: A capacitive coupled clamp-on voltage probe having three concentric cylindrical capacitive plates each separated by a thin dielectric is adapted to be clamped onto an insulated wire such as the ignition wire in an automobile to measure the potential of the wire. In one embodiment the probe contains a solid dielectric center with a slot along its longitudinal axis which extends radially from the outside to the center of the probe thereby allowing the probe to be easily positioned over and released from an automobile ignition wire by slipping the probe over any insulated portion of the wire. The slot is dimensioned to hold the wire securely at the center of the probe. The probe also includes a releasable clamp having a thumb actuated lever to assist in maintaining the wire securely at the probe center and to permit easy positioning and release of the wire.

Abstract: Diagnosing an internal combustion engine includes full throttle, specific speed tests such as measuring fuel pressure at two checkpoint speeds and at rated speed, and determining the pressure and speed where the governor reduces fuel pressure, an aneroid checkpoint of fuel pressure as a function of engine speed, and a fuel inlet restriction test, all without a dynomometer. The tests are performed with the throttle wide open, so that pressure can be measured downstream of the throttle at accessible taps, and/or to provide maximum fuel-flow test conditions. The speed comparisons are made during an acceleration with the throttle fully open, the instantaneous speed of which is accurately determined by flywheel tooth sensing.

Abstract: Indications of speed of an internal combustion engine are derived from an engine member rotating directly with the crankshaft, such as the teeth on the flywheel, so as to provide indications for speed measurements on a sub-cycle basis (that is, many times during each revolution), a timer is started after a threshold speed is reached as determined by comparison with the sub-cyclic speed indications, and a measurement of speed is made contemporaneously with starting the counter; after an elapsed time interval which may be on the order of several cycles, which is determined by the acceleration of the engine, the timer is stopped and the speed is once again measured. In one embodiment, the timer is allowed to run through a known large angle of revolution of the engine, such as several cycles, as is determined by counting successive signals indicating a particular cyclic angular position of the engine, after which the timer is stopped and the speed is measured contemporaneously therewith.

Abstract: A transducer mounted on the flywheel housing of an internal combustion engine senses the passage of each tooth on the flywheel of the engine. The number of teeth in the flywheel (to aid in calculating factors such as engine speed) is measured by counting teeth during one full engine cycle, as determined by successive cylinder identification pulses, and the tooth count is selected from a table of industry standard numbers of permissible teeth as the one which is within two teeth of the count measured by either of the methods described hereinbefore. Display of the selected number of teeth is made without an error indication if within two teeth of a standard number from a table; if not within two teeth of a standard number, the measured number is displayed, and error is indicated. The operator can select the displayed number of teeth or enter a number which he chooses.