Automotive Technology/Engine Vacuum Test

The vacuum gauge should be directly connected to the intake manifold. Desirable vacuum is 17 to 22 inches of vacuum.

Readings

• Slightly low reading shows late ignition timing

• Very low but stay shows intake manifold has a significant leak

• if on idle, you slowly go back and forth 11 and 16, you have a fuel problem

• burned and leaky valve fluctuate between 12 and 18

• Weak valve springs fluctuate between 10 and 25

• leaky Head Gasket between 7 and 20

• sticking valve between 14 and 18

• on acceleration and high rpm, if vacuum slowly rises, exhaust restriction