Vacuum Supply Test - 3.7L / 4.7L

VACUUM SUPPLY TEST - 3.7L / 4.7L









Actual engine vacuum, a vacuum reservoir (9) equipped with a one-way check valve, and vacuum lines (2) are used to supply vacuum to the speed control servo.

1. Remove rubber air tube between throttle body and air filter housing to gain access to speed control servo.

2. Disconnect vacuum hose at speed control servo and install a vacuum gauge into the disconnected hose.

3. Start engine and observe gauge at idle. Vacuum gauge should read at least ten inches of mercury.

4. If vacuum is less than ten inches of mercury, determine source of leak. Check vacuum line to engine for leaks. Also check actual engine intake manifold vacuum. If manifold vacuum does not meet this requirement, check for poor engine performance and repair as necessary.

5. If vacuum line to engine is not leaking, check for leak at vacuum reservoir (9). Disconnect vacuum line at reservoir and connect a hand-operated vacuum pump to reservoir fitting. Apply vacuum. Reservoir vacuum should not bleed off. If vacuum is being lost, replace reservoir.

6. The reservoir (9) is equipped with an integral one-way check valve to retain a certain amount of vacuum within the reservoir. Verify operation of one-way check valve and check it for leaks.