1. Disconnect the #20 vacuum hose from the vacuum manifold tubes near the emission control box.
2. Without turning on the ignition, create a vacuum in the hose. If vacuum is not achieved, replace the solenoid valve.
3. If the attached vacuum pump still shows vacuum, turn the ignition key to "START". The vacuum must be gone. If not, check for voltage at the valve (with ignition key in position "START"). If there is voltage, replace the valve.