Abstract: With a transistor ignition system, in order to generate an ion current measurement signal at the secondary end, the ignition transistor, following an ignition triggering impulse, will be driven such that a saw-toothed collector current results as a primary current, and whose rate of increase is selected such that the quasi-stationary direct voltage generated hereby at the secondary end will not trigger any ignition process. The advantage is that for generating such a measurement signal as well as for its evaluation only a few components are required.

Abstract: A method for detecting the presence of a spark in an electronic ignition system. The method consists of generating an overvoltage event and then generating a voltage signal proportional to the overvoltage event. The onset of the overvoltage event is detected by comparing the voltage signal to a starting threshold voltage and in response is provided a first signal at a high logic level. The first signal is maintained at said high logic level during the time duration of the overvoltage event. The termination of the overvoltage event is detected by comparing the voltage signal to an ending threshold voltage, which is lower than the starting threshold voltage and proportional to a supply voltage of the electronic ignition system, and in response is provided a second signal at a low logic level. The time duration of the first signal is detected and then the presence of a spark is signalled if said time duration exceeds a reference value.

Abstract: A control system for determining combustion quality in a combustion chamber of an internal combustion engine. For each combustion chamber, first and second sampling windows are generated and ionic currents sampled utilizing the spark plug as an electrode. In response to the samples, indications of combustion quality such as misfire, late combustion, and slow combustion are provided. When the engine is operating in a lean burn mode, rich correction are made to the engine air/fuel ratio in an amount dependent upon the combustion quality indications.

Abstract: An ion current detection apparatus for detecting an ion current caused by combustion in a cylinder of an internal combustion engine comprises an ion current detection circuit for detecting the ion current, a gain adjustment circuit for controlling to keep the magnitude of low frequency components of the detected ion current at a constant value, an amplifier for amplifying high frequency components of the detected ion current and outputting a high frequency component detection signal, a magnitude detection circuit for detecting the magnitude of the detected ion current to output an ion current detection signal when the detected magnitude is larger than a predetermined value, and a comparator for comparing the high frequency component detection signal with the ion current detection signal delayed by a delay circuit to output a knocking detection signal.

Abstract: A misfire detecting device for an ignition system, comprises high voltage applying means for applying a pulsed high voltage to each spark plug of an engine after completion of firing of the spark plug, voltage restricting means for restricting a peak of the pulsed high voltage to a highest possible value that does not cause firing of the spark plug, voltage detecting means for detecting a plug voltage across a center electrode-to-outer electrode of the spark plug after reducing the same, and misfire detecting means for detecting a misfire at each cylinder on the basis of a decay characteristic of a detection voltage which is caused by application of the pulsed high voltage.

Abstract: An ignition circuit IG converts a battery voltage into a high spark plug discharge voltage. A resistor R1 inserted into the power supply path L detects the current flowing through the ignition circuit by converting the current into a voltage, and a level shift circuit LS shifts the potential level at both terminals of the detection resistor. A level deviation detection circuit regulates the level of a deviation voltage developed across the detection resistor, which is caused when an electric current flows from the battery to the ignition circuit, and outputs the deviation voltage. A reference voltage generation portion sets a reference voltage to be compared with the deviation voltage by a comparator COM. A clamping circuit CL suppresses variations in the power supply voltage corresponding to the level deviation detection circuit and the comparator, and protects the level deviation detection circuit.

Abstract: A method of detecting a misfire of a gasoline internal combustion engine is provided. By this method, a high voltage pulse which is not so high as to cause spark discharge, is applied to a secondary winding side of an ignition coil by way of a diode during the time after completion of spark discharge and before generation of a high voltage for next ignition, a misfire at each cylinder is detected on the basis of a decay characteristic of a voltage at a cathode side of the diode, and a charge accumulated at the secondary winding side of the ignition coil is forcedly discharged before a next high voltage pulse is supplied to the secondary winding side. A device for carrying out the above method is also provided.

Abstract: An apparatus is provided for monitoring ignition in individual cylinders of a multi-cylinder engine of the type having an ignition system which includes a separate transformer for each cylinder. Each transformer has primary and secondary coils. The secondary coil is connected in series with a spark gap in an associated one of the cylinders. The ignition system further includes selector switches for receiving cylinder select signals and responsively connecting respective transformer primary coils. The current flows through the primary coil resulting in a voltage potential across an associated spark gap which normally increases to a magnitude sufficient to cause a spark across the spark gap. A first circuit receives the cylinder select signals, senses time delay between the reception of a cylinder select signal and sparking in a respective cylinder and responsively produces a delay signal indicative of the sensed time delay.

Abstract: An internal combustion engine misfire sensing circuit comprises an ion current sensing circuit for sensing an ion current in the combustion chamber of an internal combustion engine, a current/voltage conversion circuit for converting the sensed ion current into a voltage and a waveform shaping circuit for shaping the waveform of an output of the current/voltage conversion circuit. The waveform shaping circuit includes a second comparator for comparing a voltage of a third capacitor with first and second reference voltages for outputting a misfire sensing signal and a capacitor charging/discharging circuit for charging the third capacitor in response to the rising up of an output of the current/voltage conversion circuit and discharging the third capacitor based on the input of the misfire sensing signal. With this arrangement a misfire can be sensed even in an internal combustion engine having multiple cylinders, the number of parts can be reduced as well as the area of circuits can be reduced.

Abstract: In a capacitive discharge ignition system there being a first circuit detecting the voltage across the storage capacitor marking the onset of discharge of the storage capacitor, a second circuit detecting the voltage across the storage capacitor marking the substantially complete discharge of the storage capacitor, a third circuit for measuring the time between the events marked by the first and second circuits, and a fourth circuit for analyzing the measured time to determine conditions in the ignition system.

Abstract: A misfire detecting device for an internal combustion engine is provided.

Abstract: A method of detecting a misfire of an ignition system for an internal combustion engine is provided. By the method, after completion of spark discharge of a spark plug, a high tension pulse which is not so high as to cause spark discharge is applied to each spark plug by way of a reverse current preventing diode and a secondary winding of an ignition coil or by way of a reverse current preventing diode and a leakage preventing diode for preventing ingress of an ignition high voltage. Misfire at each cylinder is detected on the basis of a voltage attenuation characteristic at a passing side terminal of the reverse current preventing diode. A device for carrying out the above method is also provided.

Abstract: A misfire detecting device for an ignition system, comprises high voltage applying device for applying a pulsed high voltage to each spark plug of an engine after completion of firing of the spark plug, voltage restricting device for restricting a peak of the pulsed high voltage to a highest possible value that does not cause firing of the spark plug, voltage detecting component for detecting a plug voltage across a center electrode-to-outer electrode of the spark plug after reducing the same, and misfire detecting device for detecting a misfire at each cylinder on the basis of a decay characteristic of a detection voltage which is caused by application of the pulsed high voltage.

Abstract: In an apparatus and method for diagnosing presence of absence of a (wire) breakage in electromagnetic coil means such as a duty ratio controlled solenoid or at least one exciting coil portion between an end of a stator coil and a tap of a stepping motor, a checking circuitry is connected to a junction between the electromagnetic coil means and a driving transistor (switching element) to provide a checking pulse signal which provides a particular level only when an input duty ratio (pulsewidth modulated) signal is at a predetermined non-actuation (low) level and no breakage in the electromagnetic coil means occurs. In the embodiment, the checking pulse signal is sampled at a predetermined sampling period which is shorter than the period of the pulsewidth modulated signal. A historical memory in a sub CPU records (stores) a history of the sampled checking pulse signal.

Abstract: An ionization current sensing circuit providing a way to detect the combustion event in a spark ignited engine cylinder. The presence of an output signal from the proposed circuit indicates that a flame exists and that combustion has occurred in the cylinder. This signal is drastically changed if combustion is absent, the circuit providing viable engine misfire detection. The ionization current sensing circuit comprising a power source for providing voltage directly to the primary winding of the ignition coil, an integrator for integrating a spark plug ionization current and thereby providing a voltage output in proportion to the integral of the ionization current, and an ionization current sensing module for sensing a spark plug ionization current, the ionization means connected between the secondary winding of the ignition coil and the integrator means.

Abstract: An ignition system is provided for internal combustion engines for detecting combustion misfirings. The ignition system of an internal combustion engine detects the spark voltage transformed on to the primary side of a double spark coil for evaluating the ignition spark duration and/or the ignition spark voltage so as to allow a comparison to be made with limit values for a correct ignition. The limit values for a correct ignition are determined from the measured variables of a reference ignition. The reference ignition is the ignition which is triggered by the energy potential of the same ignition coil.

Abstract: A misfire detecting device for a double-ended distributorless ignition system is provided. The device includes a pulse generating circuit for generating a positive polarity pulse which is not so high as to cause spark discharge during the time after completion of spark discharge and before beginning of application of an ignition high voltage for next spark discharge. A reverse current preventing diode is connected at an anode to an output end of the pulse generating circuit and at a cathode to a positive polarity side of a secondary winding of an ignition coil. A plug voltage dividing circuit for dividing a plug voltage is connected between a center electrode and an outer or ground electrode of each of spark plugs to obtain a divided voltage. A detecting circuit detects a misfire of the spark plugs on the basis of an attenuation characteristic of the divided voltage after application of the positive polarity pulse.

Abstract: A misfire-detecting system for an internal combustion engine detects occurrence of a misfire in the engine, based on voltage between both ends of a spark plug assumed when sparking discharge takes place at the spark plug. A diode is arranged in an ignition secondary circuit of the engine, for checking reverse current flowing in the circuit in a direction reverse to the direction of flow of current occurring when spark ignition takes place at the spark plug. An ECU detects reverse current flowing in the ignition secondary circuit, and detects an abnormality of the diode, based on the detected reverse current.

Abstract: An ignition coil tester for testing ignition coils associated with motor vehicles. The ignition coil tester includes an oscillator for simulating an output signal from the ignition module associated with the ignition coil being tested. A short circuit detector is provided for detecting a short circuit within the ignition coil. An open coil indicator is proved for indicating an open circuit within the ignition coil. A series of visual indicators are provided for indicating the strength of a signal being output by the ignition coil.

Abstract: High voltage transformer, in particular an ignition coil for a combustion engine, with a conductor section carrying a high voltage with respect to a reference potential (earth) and with at least one conductor surface in the proximity of the conductor section, and galvanically separated therefrom to which a voltage is applied, the variation of which is dependent upon the high voltage. Between the conductor surface (7, 7') and a test output (12) a non-linear electrical transmission element (13) is interconnected.

Abstract: An ignition system for internal combustion engines serves as a bracket circuit arrangement (10, 11, 12, 16) to limit the primary voltage, in order to protect parts energized with high voltage from being destroyed. The ignition system comprises a voltage bracketing of the ignition transistor (3), the bracketing voltage being variable in dependence upon a secondary-side load. The primary voltage (U.sub.P) is acquired by an evaluation unit (9) and, given a high secondary load, a high bracketing voltage is used and, given a low secondary load, a low bracketing voltage is used.

Abstract: A device is provided for detecting high-voltage characteristics in an ignition system having at least two ignition coils. The device includes a plurality of first capacitive signal couplers each being disposed on a respective one of the ignition coils for capacitively extracting a voltage signal from the ignition coil. A circuit arrangement is connected to the plurality of first capacitive signal couplers and includes an output, and a signal combiner for combining the voltage signals extracted from the ignition coils and producing a combined voltage signal at the output. A plurality of second capacitive signal couplers each connected between the signal combiner and a respective one of the first capacitive signal coupler provides for potential isolation between the plurality of first capacitive signal couplers and a further portion of the circuit arrangement.

Abstract: An apparatus for combustion condition diagnosis has an ionic current detecting circuit for measuring a voltage at the secondary side of the ignition coil of an engine during a plurality of time periods during one operation cycle including a period in which an internal pressure of a cylinder of the engine becomes maximum, under a normal combustion condition. A window generation circuit is provided for establishing the time periods, an integration circuit is provided for integration processing of the measured voltage during each time period, a ROM stores a list indicating combustion condition corresponding to the integrated value for the each time period, and a CPU diagnoses the combustion condition based on the integrated value for the each time period and the list of combustion conditions, in order to decrease erroneous judgement and perform more adequate combustion condition diagnosis.

Abstract: A misfire-detecting system for an internal combustion engine detects a value of the sparking voltage generated by the igniting device after generation of the ignition command signal, determines the duration of a discharge of a spark plug, based upon the detected sparking voltage, and determines whether or not a misfire has occurred in the engine, based upon the determined duration of the discharge. For example, the misfire-detecting system measures the duration of the discharge from the time of generation of the ignition command signal, based upon the detected sparking voltage, compares the measured duration of the discharge with a predetermined time period. When the measured duration is shorter than the predetermined time period, it is determined that a misfire has occurred in the engine.

Abstract: A misfire-detecting system for an internal combustion engine detects values of operating parameters of the engine, determines ignition timing of the engine, based upon detected values of operating parameters of the engine to generate an ignition command signal indicative of the determined ignition timing, generates high voltage for causing generation of sparking voltage across a spark plug for discharging the spark plug, according to the ignition command signal, detects a value of the sparking voltage generated across the spark plug when the high voltage is generated, compares the detected value of the sparking voltage with a predetermined reference value, and determines whether or not a misfire has occurred in the engine, based upon results of the comparison. It is determined that the system is abnormal, when it is determined that no misfire has occurred while fuel supply to the engine is being interrupted.

Abstract: An engine control apparatus capable of detecting occurrence of abnormality in the ignition coil with high reliability. The apparatus includes an initial detection level hold device for holding an initial level (In) of a detected ion current value I, and an ignition coil diagnosis device for generating an abnormality decision signal of the ignition coil in dependence on the initial level of the ion current. By positively utilizing noise produced in an initial phase of the ignition cycle instead of eliminating it, the abnormality decision signal is generated, on the basis of which an appropriate engine protection measure is taken.

Abstract: An ignition device for a multi-cylinder engine includes a plurality of integral ignition device units 9A and 9B associated with respective cylinders. A single ignition detector circuit 8, inserted between the battery 1 and the primary coil of the ignition coil 5 of respective units 9A and 9B, generates an ignition confirmation signal upon detecting a current exceeding a predetermined level.

Abstract: A device for generating a trigger signal from ignition pulses of an ignition system, in which each one of the ignition pulses occurring in the ignition system is represented regardless of whether the ignition process is suppressed or not. The device can be connected to an ignition system which has at least one ignition coil with a primary winding and at least one secondary winding, where the first terminal of the primary winding is connected to the first terminal of a voltage source and the second terminal of the primary winding is connected by means of a controllable switch with a second terminal of the voltage source.

Abstract: A direct current power supply applies a positive voltage between the center electrode and the ground electrode of a spark plug in an internal combustion engine after discharge of the spark plug. Ionic current flowing between the electrodes due to the positive voltage is measured by a current sensor. The ionic current caused by the positive voltage is due to electrons, so it has a large magnitude and can be easily measured.

Abstract: Methods and apparatus for detecting low impedance short circuits in a secondary winding circuit of a coil of a distributorless ignition system (DIS) by analyzing spark discharge signals on a primary winding of the ignition coil. In one embodiment, the duration times of the spark discharge signals are compared to a threshold spark duration time, with a low impedance short circuit being indicated if the threshold spark duration time is exceeded. In another embodiment, two or more spark dwell signals are applied to the primary of the ignition coil for each spark event of each associated pair of engine cylinders. A first or base time period is determined for the first dwell signal by measuring the time it takes the first dwell signal to produce a preselected current flow in the primary winding. A second time period is then determined by measuring the time it takes the second dwell signal to produce the same preselected current flow in the primary winding.

Abstract: The ignition device of an internal combustion engine has at least one ignition coil in an ignition coil assembly and a secondary side device for ignition testing by detection of a secondary voltage signal from a secondary side from the ignition coils. The device for detecting the secondary voltage signals includes a standard measuring point device (13) at the outer periphery (P) of each ignition coil assembly, comprising advantageously a capacitive electrode, for capacitive read out of the secondary voltage signal from the secondary side of each of the ignition coils (1) in each of the ignition coil assemblies. A conductor (12) is connected electrically with the measuring point device (13) and capacitively to another conductor (8) connected to the secondary side of the ignition coil to transmit the secondary voltage signal from the secondary coil of each ignition coil (1) to the measuring point device (13).

Abstract: A misfire-detecting system for an internal combustion engine detects a value of sparking voltage generated after generation of an ignition command signal, compares the detected value of sparking voltage with a predetermined voltage value, and determines whether or not a misfire has occurred in the engine, based upon results of the comparison. The determination as to occurrence of the misfire is effected, based upon results of the comparison between the detected value of the sparking voltage and the predetermined voltage value, obtained within a previously set limited comparison period.

Abstract: A misfire-detecting system detects a misfire occurring in an internal combustion engine in such a manner that a value of discharge current is detected when sparking voltage is generated in response to an ignition command signal, the detected value of discharge current is compared with a predetermined current value, and it is determined that a misfire has occurred when a time period over which the detected discharge current value after generation of the ignition command signal is above the predetermined current value is shorter than a predetermined time period.

Abstract: An ignition detecting device for use in an internal combustion engine. An ignition surge current detector detects an ignition surge current due to capacitive discharge of the ignition coil. A comparator compares an output voltage detected by the ignition surge current detector with a predetermined reference voltage to detect accurately occurrence or non-occurrence of ignition spark.

Abstract: A misfire-detecting system detects a misfire occurring in an internal combustion engine. A value of sparking voltage after generation of an ignition command signal indicative of ignition timing is detected and compared with a predetermined voltage value, and it is determines based upon the results of the comparison whether or not a misfire has occurred in the engine. The determination as to occurrence of the misfire is based upon at least one of a time period over which the detected value of the sparking voltage exceeds the predetermined voltage value, and an area of a portion of detected values of the sparking voltage exceeding the predetermined voltage value.

Abstract: The ignition performance monitoring method and apparatus determines the time period during which the current generated in the primary winding of an ignition coil by a pulse from a capacitive discharge ignition system takes the decay to a zero ampere level and uses this determined period to calculate and indicate the firing voltage required to fire a spark plug. The apparatus includes a current sensor connected to sense the current in the primary winding of the ignition coil and a comparator to compare the sensed current with a reference indicative of a zero ampere current level. The comparator provides an output signal having a pulse width indicative of the time the sensed current was above the zero ampere level to a processor which uses the output signal and data values unique to the ignition coil employed to determine a firing voltage for a spark plug fired by the ignition coil.

Abstract: A device for testing ignition coils from automobile and other spark ignition engines is disclosed which is a small, handheld ignition coil tester powered by the battery of the engine's ignition system. The coil tester provides a visual indication of proper high voltage pulse generation or, in the case of improper function of the ignition coil caused by a short in the ignition coil, provides an indication of the existence of the short in the ignition coil. The coil tester includes a spark gap module which has vacuum sealed electrodes to provide an excellent visual indication of proper coil operation.

Abstract: An ignition apparatus for an internal combustion engine is provided in which malfunctions due to noise induced by a high ignition voltage can be avoided in a reliable manner. A controller controls the ignition timing of a cylinder of the engine in synchronism woth the rotation thereof. A detector 7-13 detects an ion current which is generated between the electrodes of the spark plug upon combustion of an air/fuel mixture in the cylinder. A filter 21 is connected to an input side of the detector for filtering noise contained in the ion current, the noise being induced by the ignition coil upon sparking of the spark plug. The ignition coil has a primary winding connected to the controller and a secondary winding connected to the spark plug. The filter is connected between the detector and a node P2 between the secondary winding of the ignition coil and the spark plug.

Abstract: A method of electronic engine control for a motor vehicle includes sensing an ignition voltage of a final ignition stage, effecting a performance check of the final ignition stage in response to a control signal generated in response to sensing the ignition voltage of a final ignition stage, and providing an error flag if the control signal deviates from a predetermined control signal. An apparatus for performing the foregoing method comprises an electric control circuit that includes a sensor for detecting the ignition voltage, and control means that effects a performance check in response to a sensor output signal and emits the error flag in response to an error control signal.

Abstract: An ionization current detector for detecting the combustion states of an internal combustion engine is disclosed, which comprises: a high voltage generation circuit means, including a series circuit of a resistor, a diode, a capacitor, and a Zener diode, coupled across the output terminal of the ignition coil and the ground; diodes coupled across the peripheral terminals of the distributor and a negative terminal of the capacitor; and a current detector circuit including a resistor coupled across the positive terminal of the capacitor and the ground and a voltage divider for detecting the amount of the ionization current. An additional Zener diode is coupled in parallel with the capacitor to limit the voltage across the capacitor. The whole detector is incorporated into a single unit mounted to the distributor cap.

Abstract: The voltage developed by a primary winding of an ignition coil is supplied to a voltage divider for furnishing an analog signal of reduced amplitude for evaluation on an analog basis, which reduced amplitude analog signal is averaged by a capacitor connected between the voltage divider tap and ground. The capacitor eliminates the undesired effect of voltage spikes, but is not large enough to interfere with the measurement of voltages exceeding the ignition-initiating primary winding voltage value. The same reduced primary winding voltage is supplied through an input resistor to one input of a differential amplifier connected to operate as a switch having hysteresis and having a reference voltage applied to it such that the output will be the provision of a steady voltage having a duration corresponding to the spark discharge duration, for subsequent digital evaluation.

Abstract: A method of and a device for monitoring combustion in a spark ignition internal combustion engine having a combustion chamber and a discharge system wherein a discharge voltage is monitored for determining whether combustion in the combustion chamber takes place.

Abstract: A circuit for recognizing missing or poor firings in Otto (gasoline) engines with multi-circuit ignition systems features a voltage tap on the primary side of each ignition coil (10, 11), leading to a respective controllable transistor (16, 19). A common junction point (21) for the respective transistors provides signals, representative of the control states of the transistors, for evaluation (32). These signals correspond to the respective spark burning voltages. The cylinders fire sequentially, so the voltage patterns of the respective cylinders appear sequentially at the common junction point, and it is possible, even in multi-circuit ignition systems, to monitor the individual ignition circuits in a simple manner, and to interrupt fuel supply to any less-than-optimally firing cylinder, thereby preventing unburnt hydrocarbon overload on the catalytic converter and on the environment. Preferably, the evaluation circuit includes an A/D converter (33) and an INTEL 8051 microprocessor (34).

Abstract: In order to protect catalytic converters from damage caused by continued engine operation with a malfunctioning ignition system, a monitoring circuit checks current in the ignition coil primary winding. Primary winding current (i) is transformed by a measuring circuit (11) into a test primary voltage (U.sub.pr) which is fed to an evaluation circuit for comparison with ignition system supply voltage (U.sub.v) from the battery. During each primary current pulse, an instantaneous value is sampled, preferably during the earlier half of the pulse, and when the instantaneous test voltage (U.sub.pr) exceeds the supply voltage (U.sub.v) by more than a predetermined amount, the evaluation circuit (10) generates an error or malfunction indication. The ignition system can then be serviced before the catalytic converter is ruined.

Abstract: An ignition apparatus for an internal combustion engine has first and second comparators which compare the voltage of a winding of an ignition coil with reference voltages at first and second lengths of time after an ignition signal. The output of the first comparator indicates if the secondary winding of the ignition coil is connected to an open circuit. The output of the second comparator indicates if the secondary winding is shorted to ground. The comparators are connected to an OR gate, and the output of the OR gate is used to indicate misfiring.

Abstract: The method and apparatus allows the detection and indication of anomalies in the operation of the ignition system of an internal combustion engine including a plurality of spark plugs, each of which receives a periodic high-voltage pulse output by a high-voltage generator in operation. The method includes the steps of:detecting the pulses generated by the high-voltage generator,comparing the peak values of each pulse detected with first and second threshold values, andproducing a perceptible signal when the peak values of the high-voltage pulses fall outside the acceptable range defined between the threshold values.

Abstract: An inductive pickup assembly senses the electromagnetic fields of plural ignition elements of an automotive engine, access to which elements is prevented by associated engine housing structure. The pickup assembly includes a frame having a flat platform on which multiple sensors are mounted, each sensor comprising an electromagnetic pickup coil with a magnetizable metal core integral with a magnetizable metal shield plate which covers one end of the coil. The frame has a support member with depending feet having apertures which mate with fasteners on the housing structure to serve as a template for accurately locating the pickup assembly on the housing structure.

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: An apparatus for generating a synchronizing signal for a selected cylinder of a multi-cylinder engine having a double ended coil ignition system, including a comparator for identifying a real ignition pulse on the ignition device associated with the selected cylinder and a discriminator for identifying a real ignition signal on the coil energizing that ignition device and circuitry to produce a synchronizing signal only when the two coincide.