Tahoe 4WD V8-393 6.5L DSL Turbo VIN S (1995)
Vacuum Pump: Testing and Inspection
Fig. 1 Vacuum Chart.
1. Block wheels, apply parking brake, and place gear shift lever in Park or Neutral.
2. Connect vacuum gauge to vacuum pump inlet (lower port).
3. Disconnect outlet hose from outlet tube (upper port) and plug end of hose.
Do not plug vacuum pump outlet tube.
4. Start engine and run at idle. Vacuum should read as shown in Fig. 1, within 30 seconds.
5. If vacuum is below specification, or gauge reading fluctuates, proceed as follows:
a. Check gauge and connections for leaks, correcting as necessary.
b. Check belt tension and pulley fit to pump, repairing or replacing as necessary.
c. Check idle speed and correct as necessary.
d. If vacuum is still below specifications or gauge still fluctuates, replace vacuum pump and repeat procedure.
6. If vacuum is within specifications, proceed as follows:
a. Remove plug from outlet hose and connect hose to pump outlet tube.
b. Connect vacuum inlet hose to pump with a T-fitting and vacuum gauge located near pump inlet.
c. Start engine and run at idle for one minute.
d. If vacuum is three inches Hg lower than original reading, vacuum pump is not defective.
e. If vacuum is more than three inches Hg lower than original reading, check all attaching hoses for leaks, correcting as necessary.
f.
If vacuum is still too low, check all vacuum accessories for leaks, repairing or replacing as necessary.
