Engine Vacuum Supply Test
- Disconnect vacuum line at diaphragm unit. Connect vacuum line to gauge. At idle, engine vacuum must hold steady at an acceptable level for the altitude at which the vehicle is tested.
- If vacuum reading is low, check for vacuum leaks in vacuum hoses and engine vacuum related components (power brake booster, etc.).
- If vacuum reading is okay, press the accelerator pedal quickly, then release. Vacuum reading should drop rapidly then recover immediately when pedal is released.
- If vacuum reading does not change or recover quickly, check supply line for restriction or incorrect connection.