Run Mode (2-Bbl. & 4-Bbl.)

On 2-Bbl. models, the "Run" pick-up coil is the only pick-up coil used. This pick-up coil starts and runs the engine. The pick-up coil sends a reference signal to the computer. Timing is controlled by the computer, based upon information received by the data sensors. If this component fails, the vehicle will not run.

On 4-Bbl. models, once the engine starts, the "Run" pick-up coil sends a reference signal to the computer. Timing, however, is controlled by the computer, based upon information received by the data sensors. See Figure and Figure .

Spark timing and dwell cannot be adjusted in the run mode. If the computer fails, the system will go into the start mode. This enables the vehicle to be driven in for repair; but performance and fuel economy will be poor. If the start mode fails, the engine will not start or run.

On all models, the amount of spark advance is determined by engine speed and engine vacuum. However, when it happens depends upon the following conditions:

• Advance From Vacuum - Advance based upon engine vacuum is allowed by the computer when the carburetor switch is open. The amount of advance is programmed into the computer and is proportionate to the amount of vacuum and engine RPM.
• Advance From Speed - Advance based upon engine speed (RPM) is allowed by the computer when the carburetor switch is open and the vacuum level is steady. This advance from speed is programmed into the computer, controlled by engine RPM, and will build at a slow rate. If the carburetor switch closes, advance from speed will be canceled.