Vacuum Gauge Test - Typical:
1. Disconnect vacuum hose at the servo and install a vacuum gauge in the hose.
2. Start engine and observe gauge at idle. Vacuum gauge should read at least ten inches of mercury Shut off engine, the vacuum should continue to hold 10 inches of mercury
3. If vacuum does not meet this requirement, check and correct the following vacuum leaks in the vacuum lines, check valve, vacuum reservoir or check for poor engine performance.