A coil-on plug testing apparatus generates an output signal representing an ignition signal. The testing apparatus includes an inductive sensor for detecting an electromagnetic flux generated by a coil-on plug device during a firing event and generating and outputting a voltage in response thereto, and a signal processing circuit electrically connected to the inductive sensor for generating an output signal in response to variations in the voltage output by the inductive sensor. A method for determining burn time for a coil-on plug ignition includes disposing an inductive sensor adjacent to a coil-on plug ignition housing, using the inductive sensor to detect an electromagnetic flux output by the coil-on plug ignition during a period encompassing at least one firing section, and determining a burn time by identifying a firing line, identifying an endpoint of a spark line and determining a time period therebetween.

A device for monitoring operational condition of electrical consumers in a motor vehicle, particularly of heater plugs of a diesel engine, includes inductances connected in series between respective heater plugs and their d.c. supply. Alternating or pulsating current is supplied to a connection point of the inductances with the d.c. supply, and potentials across the inductances and the heater plugs are simultaneously evaluated to indicate a defective heater plug.

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. Further, in accordance with this invention, the spark plug may be caused to multiply discharge within a short duration which has been found to increase the lean burn limit of the engine. The system further enables the duty cycle of the pulse transformer to be reduced thus allowing use of smaller and lighter weight pulse transformers. The ignition system also provides a means of sensing abnormal conditions in the combustion chamber via the spark plug. Pre-ignition occurring at the spark plug electrode gap will result in a very low breakdown voltage which is detected as an indication of an abnormal condition.

An integral spark plug coil comprising a step-up coil within a canister which canister is mounted to a unique double-walled container. The container fits over the neck of the spark plug and is secured to the shell of the spark plug. An inner ceramic bushing is arranged within a metal sleeve defining the outer wall of the container. The space adjacent the neck of the spark plug is in communication with the exterior of the metal sleeve through the small quenched space defined by the inner diameter of the sleeve and the outer diameter of the ceramic bushing and through ports in the sleeve located generally outward of the terminal end of the neck of the spark plug.

A direct fire ignition system for an internal combustion engine having a coil assembly attachable to each spark plug. Each coil assembly has a high voltage transformer for producing a voltage sufficient to cause the spark plug to generate a spark, an integral capacitor parallel with the spark plug, and a spark plug sensor circuit coupling to the high voltage transformer for generating a spark confirmation signal when a spark is generated. The spark sensor circuit is responsive to a high frequency signal generated in the high voltage transformer within a predetermined frequency range to generate the spark confirmation signal. The direct fire ignition system is compatible with single strike or multi-strike modes of operation. The system can also generate a probe voltage across the spark plug to test for auto or pre-ignition.