VACUUM SYSTEM Source Vacuum Check Disconnect vacuum supply (small) hose from servo. Connect vacuum gauge to end of hose. Start engine. If gauge indicates at least 10 in. Hg, go to SERVO VACUUM VALVE CHECK procedure. If gauge does not indicate at least 10 in. Hg, check for leaking or pinched hoses. Servo Vacuum Valve Check Turn engine off. Disconnect vacuum supply (small) hose from servo. Connect hand-held vacuum pump to vacuum supply hose fitting on servo. Apply 10-15 in. Hg to servo. If vacuum holds, go to SERVO VENT VALVE CHECK procedure. If vacuum does not hold, or if vacuum decreases in less than 10 seconds, replace servo (in a good servo, vacuum will decrease in more than 30 seconds). Servo Vent Valve Check 1. Disconnect servo cable from throttle lever. Disconnect servo electrical connector. Using a fused jumper wire, apply battery voltage to Dark Blue/White wire terminal of servo connector. Jumper Black wire terminal of servo connector to ground. 2. If vent solenoid is not heard clicking, replace servo. If vent solenoid is heard clicking, disconnect hose from large fitting on servo. Connect vacuum pump to large fitting on servo. Apply 10-20 in. Hg to diaphragm. If diaphragm moves in completely and vacuum does not decrease quickly, go to BRAKE RELEASE VALVE TEST procedure. If diaphragm does not respond as specified, replace servo. Brake Release Valve Test Disconnect vacuum release hose (large hose) from servo. Connect vacuum pump to end of hose. Apply 10-20 in. Hg to hose. If vacuum does not hold, or if it leaks down slowly, check for leaking or misadjusted brake release valve. See BRAKE & CLUTCH RELEASE SWITCH/VALVE ADJUSTMENT under ADJUSTMENTS. If brake release valve is okay, check for leaking hose between servo and brake release valve. If hose is okay, replace servo. Page 1 of 1 CRUISE CONTROL SYSTEM - VACUUM SERVO (EXCEPT 3.8L) -1993 Chevrolet C... 8/15/2008
Aug 15, 2008 at 2:53 PM
