VACUUM GAUGE READINGS AND INTERPRETATIONS

note : The vacuum gauge readings are measured in inches of mercury at sea level. In all 4-cylinder engines, a slight fluctuation will always be noticeable.
This can be overcome by pinching the gauge hose slightly to enable a steadier reading.

	WEAK VALVE SPRINGS: engine running fast, the needle moves between 10 and 21.Further increase in engine speed increases needle variations.		LATE VALVE TIMING: with engine running at a higher idle speed needle reads from 8 to 15 and remains steady.
	RETARDED IGNITION: needle gives steady reading between 17 and 19 with engine running at a higher idle speed.		DEFECTIVE IGNITION: if needle moves slowly between 14 and 16 at normal idle, check ignition components (plug gaps closed up/fouled,contacts not synchronized).
	INTAKE SYSTEM LEAK: with engine running at idle or fast idle speeds needle reads between 3 and 5. Check induction manifold gaskets.		HEAD GASKET LEAK: (leaking between cylinders): needle moves backwards and forwards regularly between 5 and 17.
	EXHAUST SYSTEM BLOCKAGE: high reading when engine first started, falling back to 1 or zero and gradually increasing to 15 or 17.		INCORRECT FUEL ADJUSTMENT: needle moves slowly backwards and forwards between 18 and 21.Check engine idle mixture.