Spark Advance of Spark Control Computer Test

Fig. 5 Positioning paper insulator and carburetor switch terminal location. (Typical):

1. Ensure engine is fully warmed up and the temperature sensor is connected and operating properly.
2. Set ignition timing to specifications.
3. Place a piece of paper between curb idle adjusting screw and carburetor switch, Fig. 5, or ensure curb idle adjusting screw is not contacting carburetor switch.
4. Remove and plug vacuum transducer line.
5. Using a suitable hand-operated vacuum pump, apply 16 inch of vacuum (10 inch on 1983-86 6-255 engine or 16 inch on 1987 6-225 engine) to vacuum transducer.
6. Increase engine speed to 2000 RPM, wait 1 minute (or specified clock up time, refer to ``Electronic Spark Control Specifications''). Advance specifications are in addition to basic timing advance. On systems equipped with an accumulator the specified time must be reached with the carburetor switch ungrounded before checking the specified spark advance schedule (Refer to ``Electronic Spark Control Specifications'').
7. If the computer fails to obtain specified settings, replace computer.