Vacuum Control System

Fig. 33 Pressure Converter Vacuum Port ID:

1. Connect vacuum gauge with a "Y" fitting to EGR valve.
2. Check vacuum values and position of vacuum control flap at the following RPM's:

RPM VACUUM READING PRESSURE CONTROL FLAP POSITION
750 0 in. Hg Basic
1200 4-9 in. Hg Fully attracting
3000 0 in. Hg. Basic

3. If vacuum test values are OK, proceed to step 4. If vacuum test values are not OK, check vacuum supply and individual components.
4. At approx. 1200 RPM operate microswitch (each half in turn). Reading on vacuum gauge should drop to zero and the pressure control flap should move into it's basic position. If the switch functions properly, proceed to step 5, if it does not, test the individual components.
5. Connect vacuum gauge to vacuum connection "2" of the pressure converter, Fig.33, with a vacuum "tee" and check vacuum at idle. The pressure reading should be approx. 9.6-11 in. Hg. With engine stopped and throttle linkage at full throttle stop, the vacuum reading should drop to 0 in. Hg. If test is OK, end of test. If test is not OK, check vacuum lines and vacuum pump. Adjust vacuum control valve and replace, if necessary.