GB1531468A - Ignition coil and capacitor analyzer - Google Patents

Abstract

1531468 Testing IC engine ignition circuits UNITED TECHNOLOGIES CORP 18 Dec 1975 [19 Dec 1974(2)] 51956/75 Heading G1U An ignition circuit testing system exploits the fact that if the ignition circuit is in good condition then with the secondary winding open circuited for each cylinder firing pulse the voltage, (a), Fig. 3, across the contact breaker should rise above a certain minimum (about 250V) and should execute a certain number of oscillations. To this end, a potential divider 64, ..., 68, Fig. 1, is connected to the contact breaker so that the voltage across it can be compared with a pre-set threshold 74, and its oscillations can be squared 34 (see also (b), Fig.3) and counted. In the preferred embodiment the contact breaker voltage is examined successively over sixteen firing cycles in relation to a particular cylinder, the plug lead 28 for this cylinder being removed and being connected to a signal conditioning circuit 30 to provide appropriate gating signals. The number of firing cycles in which the contact breaker voltage exceeds the pre-set threshold 74 are counted 58, and the total number of oscillations of the voltage are counted 56, 57, so that the most significant four bits 57 represent the average number of oscillations per firing cycle. The resulting counts are then applied to a logic circuit which produces an indication of the likely condition of the ignition circuit. For example, if the number of firing cycles during which the contact breaker voltage exceeds the threshold lies in the 25% to 75% range, lead 90, and if also the average number of oscillations lies in the 4 to 10 range, lead 108, then an indication "intermittent arcing", lead 118, is produced.