DESCRIPTION
Aspirator air system consists of an aspirator valve and an aspirator tube assembly. Aspirator valve uses exhaust pressure pulsation to draw air into exhaust system, reducing carbon monoxide (CO) and hydrocarbon (HC) emissions.
Tube assembly connects aspirator valve to air cleaner at one end, and exhaust manifold at the other end.
Scheme 47
OPERATION
Aspirator valve draws fresh air from "clean" side of air cleaner, past a one-way, spring-loaded rubber diaphragm. Diaphragm opens to allow fresh air to mix with exhaust gases during negative pressure (vacuum) pulses, which occur at exhaust ports and manifold passages.
If pressure is positive, diaphragm closes and no exhaust gas is allowed to flow past valve into "clean" side of air cleaner.
Aspirator valve works best at idle and slightly off-idle, when negative pulses are at maximum. At higher engine speeds, valve remains closed.
TESTING
Aspirator valve is not repairable. If valve fails, it must be replaced. Check all connections for proper assembly. If leakage is noted at any joints, repair before testing valve.
To test aspirator valve, disconnect hose from aspirator inlet. With engine idling in Neutral, vacuum exhaust pulses should be felt at aspirator inlet. If hot exhaust gas is escaping from inlet, valve is defective and must be replaced. If aspirator hose is hard, hose must be replaced.
