Abstract: A microphone serving as a pressure gradient sensor is connected by a pressure transmission tube to the collecting duct of the exhaust manifold of an internal combustion engine for detecting the pressure shock waves released by the opening of the exhaust valves of the engine when combustion occurs in the respective cylinders. An evaluation circuit connected to the sensor detects when such a pressure wave is missing, indicating a failure of ignition in the cylinder and reports the cylinder in which such failure occurs. The system has the advantage that failure of the fuel to ignite is detected and when there is a normal spark. The counter in the evaluation system identifies the cylinder when a failure has occured. The sensor can be disconnected under control of the crankshaft or the camshaft from the evaluation circuit except during brief intervals beginning just before an exhaust valve opens, in order to improve reliability.

Abstract: An open secondary coil of an ignition coil is detected by the use of a reverse current in the primary of the ignition coil to indicate the occurrence of an open secondary coil.

Abstract: Misfiring in internal combustion engines is detected by detecting the voltage induced in the primary winding of the ignition coil, and comparing it to a reference voltage which represents normal firing. The reference voltage preferably has a predetermined magnitude and a predetermined duration and the detected and reference voltage are compared so as to detect when the magnitude of the detected voltage falls below the predetermined magnitude before the end of the duration.

Abstract: This invention relates to a number of improvements in ignition systems of spark ignition engines. A detector is employed to sense the first or "breakdown" phase of spark discharge across the spark plug which causes a short duration high current flow across the plug gap. The detection of the breakdown current enables control over a number of ignition system functions. A pulse transformer is used which enables extremely short duration energization of the spark plug at controllable voltages. The existence of end gas auto-ignition is detected by energizing the spark plug during a period of the operating cycle after top dead center of piston travel. Since the threshold voltage necessary to generate spark discharge at the plug differs in conditions where auto-ignition is occurring versus ordinary combustion, sensing of plug breakdown during such energization provides a means of detecting the occurrence of auto-ignition.

Abstract: A method of testing spark plugs in an engine is described. The engine is driven by its starter motor or other motor while ignition voltage is applied, the throttle is open and the fuel is cut off. This loads the spark plugs to reveal defects not otherwise apparent. Abnormally high or low plug peak voltages as well as abnormal arc durations are detected and counted and the counts are displayed. A microprocessor based measuring instrument coupled to capacitive pickups adjacent the spark plug wires and to the engine distributor evaluates the spark voltage and duration characteristics and displays the fault data.

Abstract: A semiautomated diagnostic apparatus primarily used with ignition systems on internal combustion engines is novel in that every firing is examined for peak breakdown voltage level in a synchronized sequential manner to create a display of abnormalities and sequence number identification. Normal conditions can also be displayed in sequence when desired. A variable input permits examining relative peak voltages for further user analysis. An acoustic alert is provided as is an RPM indication and novel realtime indication of spark advance angle. The system operates at any engine speed.

Abstract: A method and apparatus for testing ignition systems of internal combustion engines in motor vehicles, in which an ignition voltage signal on the primary side for one ignition operation or averaged for several ignition operations is compared with a should-be signal and the electrode distance of a spark plug is determined in that the should-be signal is taken at the beginning of a service interval and under an operating condition which at least approximately equals the actual operating condition at the point of time of the test.

Abstract: The Ignition Performance Measuring Circut is intended for use with dual ignition systems, such as the dual-magneto ignition systems used on light aircraft. The circuit has a first and second channel. The first channel is dedicated to measuring the relative peak amplitude of amplitude difference signals, i.e. the algebraic difference between concurrent left and right conditioned ignition signals. Signal conditioning is performed by an input attenuator and a difference amplifier. The circuit operates without benefit of a positive synchronization. To any particular cylinder's ignition firing signals. The pilot of an aircraft using the invention circuit will be alerted to the presence of a degraded firing signal but will not be advised as to which cylinder or spark plug is contributing to the failure indication. The circuit has a peak detection network for selecting the largest amplitude difference signal from each series of firing signals.

Abstract: The secondary ignition circuit of a spark ignited internal combustion engine is analyzed to identify the location of faulty portions of the circuit, the circuit having an induction coil for generating sparking voltage pulses repetitively, and a distributor for cyclically distributing the voltage pulses to respective spark plugs in a predetermined order. The peak amplitude of respective voltage pulses of one polarity developed at a single point in the secondary ignition circuit for respective spark plugs in each engine cycle is measured to produce measurement signals systematically related thereto. A comparison signal is derived that is systematically related to the average peak amplitude of voltage pulses of the one polarity developed for all spark plugs. Successive measurement signals are compared with the comparison signal, and a fault is indicated when a measurement signal differs from the comparison signal by more than a predetermined differential.

Abstract: An equipment for recognizing misfiring, which is particularly suitable for permanent installation in a motor vehicle. By means of high-pass filters coupled to the plug leads between the spark distributor and the spark plugs, the change to the voltage at the spark plugs associated with the initiation of the ignition spark is sensed. The high-pass filters are so arranged that they only send on a needle-shaped output pulse signal to an analysis circuit if it appears with the change in voltage associated with the spark front. The analysis circuit generates appropriate output signals with reference pulses generated in time with the ignition pulses. The high-pass filters are preferably arranged as simple RC filters whose capacities are coupled to the plug leads by means of peripheral electrodes, which at least partially surround the insulation coatings of the plug leads.

Abstract: This specification discloses testing vehicle primary ignition systems by taking the integral of the primary spark plug firing voltage versus time over a time period when the spark should occur. To determine when an integration output should be evaluated, a phase locked loop circuit is used to predict the occurrence of an ignition firing pulse. To compensate for changes in engine speed and yet disregard extraneous spark plug firings, the phase locked loop circuit contains two loop filters having different response times which are automatically selected to minimize response to erroneous or missing spark plug firings and maximize response to actual engine RPM changes.

Abstract: An engine analyzer, for analyzing ignition voltage or current signals in an engine of the kind in which each spark plug is fed with a succession of pulses, alternate pulses producing real sparks to ignite the petrol/air mixture, the other pulses producing wasted sparks at a point of the engine operating cycle remote from ignition, the analyzer including circuitry to pass the real spark pulse and inhibit passage of the wasted spark pulses.

Abstract: The device for testing an ignition system of a combustion engine comprises an adjustable load connected in the primary winding of the ignition coil by means of which the stored energy is so long reduced until due to the deficient energy the first ignition slip of the fuel-air-mixture occurs. This reduced energy is compared with the nominal or normal energy required for proper operation of the ignition system and the difference between the two values determines a measure for ignition energy reserve and consequently a measure for the condition of the whole ignition system. The energy reserve is measured selectively always for a part of the ignition system, that means for a cylinder of the engine. For this purpose a selective switch is employed using a scaler fed by pulses derived from the contact breaker and synchronized by a pulse from the part of the cylinder under test produce an output pulse which connects the loading member to the primary winding of the ignition coil.