Econoline E250 3/4 Ton V8-5.4L CNG VIN M (1998)
Vacuum Brake Booster: Testing and Inspection
1. With the transmission in NEUTRAL and the engine stopped, apply the brakes several times to exhaust the vacuum in the vacuum boost system.
2. Hold the brake pedal in the applied position.
3. Start the engine.
4. If the power brake system is functioning properly, the brake pedal can be felt to move downward after the engine starts.
5. With a vacuum type power brake booster, if engine vacuum is available to the power brake booster and no power assist is felt, replace the power
brake booster and retest the system
