Adjusting Control Valve
- Connect vacuum gauges as shown in illustration. Gauges must have accuracy of ± 1/2" Hg over its operating range. Open throttle gently by hand and increase speed slowly to 3000 RPM.NOTE: Values for inches of mercury given below are for 1972-73 models. For 1970-71 models add 1" Hg to these values.
- Observe vacuum gauges. One gauge will indicate manifold vacuum and should rise from about 17" to 19". Second gauge reads zero when control valve is closed, and slightly less than manifold vacuum when control valve is open.
- Control valve should not open as manifold vacuum rises to 19". If valve opens, stop engine to bleed vacuum, and screw adjusting nut clockwise to increase spring tension.
- Repeat procedure until valve does not open at 19". Then increase engine speed to 3000 RPM and close throttle very slightly. Observe the slight rise in manifold vacuum. Control valve should now be adjusted so that it opens at 20" manifold vacuum.
- Run engine at 2500 RPM and release throttle. Engine should slow to idle in 4-6 seconds. If engine remains at 1500-1700 RPM, stop engine and allow to cool for 10 minutes (hood up).
- Repeat test and if engine still does not return to idle, recheck that control valve does not open below 19" manifold vacuum. If this setting is still correct, control valve is faulty and must be replaced. Remove all test equipment, reinstall hoses and other components, and finally recheck time to slow down from 2500 RPM to idle.