This component has undergone an enormous development. The distributor cap, one of the first plastic parts in the automobile, was found in nearly every four-stroke petrol engine. It was however, often also the cause of breakdowns. Dampness or also small cracks could cause current creepage, which weakened the tension to the spark plugs. The small carbon contact in the center (from cable 4), which was pressed onto the rotor arm by a small spring was also sometimes lost. Surrounding it were the contacts for the four spark-plug leads, these were passed closely by the rotating arm. What was important here, was the built-in interference-suppression (1) between the center- and the outer copper tongue. A defect here, could justify the replacment of the rotor arm. Under no circumstances could one simply bridge the gap, the result would have been, e.g., radio interference in the vehicle next to yours.
Interference suppression was also a point to be considered as far as the previous plug-leads were concerned. Plug-leads with a carbon-fibre core were especially well suited. These were however, often also the cause of ignition problems. Fortunately nowadays, there are any number of ways to avoid these rather delicate components. Possible errors in the ignition are nowadays, no longer the focal point in the workshops.
The distrubutor cap in a six-cylinder - apart from the number of plug-lead contacts - is the same concept as in the four-cylinder. In the eight-cylinder, there was either one distributor or - because of the larger diameter - the plug-leads were supplied by two distributors. 08/11