Orifice Spark Advance Control: Testing

Inspect all hoses for leaks or damage. With engine running at 2000 RPM in neutral, disconnect hose at OSAC valve that leads to distributor. Attach vacuum gauge to fitting. Valve is operating properly if a very gradual increase in vacuum is observed, about 20 seconds to a stabilized level (this will vary with different engines). If vacuum immediately goes up to same level as manifold vacuum, OSAC valve is bad and must be replaced. If no increase in vacuum is observed, OSAC valve is also bad and must be replaced.

NOTE: OSAC valve may be by-passed during very hot engine operating temperatures. See Chrysler Corp. NOx System Temperature Operated, Vacuum By-Pass Valve (Thermal Ignition Control Valve).