1977-79 Single Pick-Up Distributor Models

The Spark Control Computer functions in 2 modes, the start mode and the run mode. During engine cranking the start mode is in operation. A fixed advance is established in the ignition system during this mode. The pick-up coil tells the computer that the engine is in the cranking/start mode.

When the engine is started, the run mode takes over. The pick-up coil signals the computer during the run mode; however, the amount of advance will be determined by the signals received from all system sensors.

Should the run mode fail, the start mode will take over. At this point, the fixed amount of advance will again be supplied and engine operation will continue but will be below standard.

If the computer should fail, the system will switch to the "limp-in" mode. This will enable the engine to continue running, but poor performance will be experienced. Should the pick-up coil or start mode of the computer fail, the engine will not start.