Vacuum System Inspection (Vacuum Circuit Functional Test)
- Before starting engine, disconnect bead chain or cable from servo. Disconnect electrical leads at vacuum control and solenoid valves.
- Actuate vacuum control and solenoid valves by connecting jumper wires to one terminal of each valve to ground, and a jumper wire from the other terminals to battery.
- Start and run engine at idle. With brake pedal released, servo diaphragm should pull in to full stroke. Depress brake pedal about 1 1/2" and servo diaphragm should relax to the free position, indicating that vacuum brake release valve and hose are okay.
- If system will not hold vacuum, remove brake release valve vent hose from servo and plug servo vacuum fitting (manifold vacuum should be open).
- If servo diaphragm draws in, problem is in brake release vacuum vent system. If servo will not draw in, inspect servo diaphragm and vacuum connectors at all vacuum valves.