Single-Function For Standard Cooling (6-Cylinder & V8 Engine)

Connect vacuum gauge to center port "D" of CTO switch. When coolant is below 155°F (68°C), manifold vacuum should register. Above 155°F (68°C), carburetor ported vacuum should register. If valve does not meet these requirements, it must be replaced. See Figure .

Fig 1: Vacuum Spark Control Delay Valve (4-Cylinder)

Courtesy of AMERICAN MOTORS/JEEP CORP.