Federal 2WD Models
The fresh air is supplied to the exhaust ports of both cylinder heads through Air Suction Valve-I with cut-off valve. The air injection to each cylinder head is controlled by separate air suction valves.
When coolant temperature is below 95° (35°C), the electronic control module signals the solenoid valve to allow manifold vacuum to open the cut-off valves. This enables the air suction valves to operate. The solenoid valve remains open for a period of 123 seconds. During this time, if low vacuum condition should exist, a check valve is used to maintain vacuum at the solenoid and the cut-off valves.
At the end of the 123 second period, the control module turns off the solenoid valve signal. Vacuum is no longer supplied to the cut-off valve and air injection is terminated.
A third air suction valve (ASV-II) without cut-off valve supplies fresh air to the exhaust port near the up stream portion of the oxidation catalyst. An ASV without cut-off valve always operates regardless of coolant temperature and electronic control module signal. See Fig 1 .