How to Use a Vacuum Gauge?
2 Answers
How to use a vacuum gauge: 1. Before testing, adjust the initial ignition timing and idle speed limit. Connect both ends of the vacuum gauge to the vacuum pump and the equipment that needs to be vacuumed. Open the valve and start the vacuum pump. At this time, the pointer swings counterclockwise, moving from 0 towards -0.1; 2. When the pointer is at -0.1, it is close to a vacuum but not equal to a vacuum; 3. After turning off the vacuum pump for a period of time, if the pointer points to 0, it indicates a vacuum. Vacuum gauges are divided into pressure vacuum gauges and vacuum pressure gauges. A vacuum pressure gauge uses atmospheric pressure as a reference and is used to measure pressures less than atmospheric pressure; a pressure vacuum gauge uses atmospheric pressure as a reference and is used to measure pressures both greater and less than atmospheric pressure.
Using a vacuum gauge to diagnose a car engine is quite simple. I start by parking and turning off the engine, locating the vacuum port on the engine intake manifold, and ensuring the surface is dry and free of oil. Connect the vacuum gauge's hose to the port and tighten the fitting to prevent air leaks. Then, start the engine and let it idle. After stabilizing for a few seconds, observe the vacuum gauge needle: a normal reading should remain steady between 17 to 22 inches of mercury. If the needle fluctuates up and down, it may indicate damaged valves or piston rings; if the reading is too low, below 15 inches, it could be a vacuum leak or intake issue; if it's too high or shows zero abnormally, check the spark plugs or exhaust system. Safety first during operation—keep away from rotating parts, and testing after the engine warms up yields more accurate results. Regular use of a vacuum gauge can detect air leaks early, avoiding major repairs due to increased fuel consumption or power loss.
