Lesson3/Learning Event 2
FIGURE 23. TYPICAL AUTOMOTIVE IGNITION SYSTEM.
The points consist of two contacts: one is stationary and grounded and the other is insulated and
movable. When mounted in the distributor, the spring end of the movable breaker arm assembly is
connected to the primary lead from the coil. The breaker arm is mounted on a pivot post and is
insulated from the post by a fiber bushing. The entire arm can swing back and forth on the pivot
post. A fiber rubbing block is kept in contact with the distributor cam on the distributor shaft
during the time the breaker points are open. The distributor shaft is driven in time with and at
one-half the speed of the engine crankshaft. On most distributors, the cam will have one cam lobe
for each cylinder of the engine. The grounded point is attached to a support which, in turn, is
mounted on a plate inside the distributor. While this point is often called the stationary point, it
can be moved to adjust the point opening. This is done by moving the adjust able point either
nearer to or farther from the insulated point.