DESCRIPTION
The air injection system is designed to reduce hydrocarbon (HC) and carbon monoxide (CO) emissions by supplying filtered air to the exhaust manifold.
The system consists of an air injection valve, air injection control solenoid valve, pressure regulator control solenoid valve, water temperature sensor and ECCS control unit. The air injection valve is controlled by the ECCS control unit, corresponding to engine temperature.
OPERATION
The Air Injection System is designed to send secondary air to the exhaust manifold, utilizing a vacuum created by exhaust pulsations in the exhaust manifold. Exhaust pressure in the exhaust manifold usually pulsates in response to opening and closing of exhaust valves, and periodically it decreases below atmospheric pressure. When this happens, a vacuum is created and a secondary air intake is opened, allowing secondary air to be drawn into the exhaust manifold in direct proportion to the vacuum.
AIR INJECTION VALVE
The Air Injection Valve (AIV) is a dual reed type check valve. When exhaust pressure is lower than atmospheric pressure (negative pressure), the valve is open and secondary air is sent to the exhaust manifold. When exhaust pressure is higher than atmospheric pressure, valve is closed and secondary air injection is shut off.
AIR CONTROL SOLENOID VALVE
The AIV control solenoid valve cuts intake manifold vacuum signal for AIV control. The solenoid valve actuates in response to the ON/OFF signal from the ECCS control unit. When the solenoid is off, the vacuum signal from the intake manifold is cut. As the control unit outputs an ON signal, the coil pulls the plunger downward, and feeds the vacuum signal to the AIV control valve.
THERMAL VACUUM VALVE
The thermal vacuum valve detects engine coolant temperature by means of wax expansion and opens or closes the air passage from the air cleaner. When the air passage is closed, the carburetor vacuum signal is applied to the diaphragm of the EGR control valve to actuate the taper valve connected to the diaphragm.
AIV Main Components. Scheme 8
- Disconnect cylinder head temperature sensor harness connector and connect a resistor (2500-ohm) between the terminals of cylinder head temperature sensor harness connector.
- Start engine and check whether the AIV operates by listening to the operating sound, or by checking for vacuum at AIV. If not okay, go to next step. If okay, disassemble AIV case and check AIV control valve and reed valves for binding or damage. Replace malfunctioning part. If okay, check cylinder head temperature sensor. If this is okay, end test.
- Check AIV control solenoid valve for continuity. Connect leads of ohmmeter across terminals of AIV connector. Resistance should be 30 ohms. If not, replace the solenoid valve. Check AIV control solenoid valve for operation.
- Turn ignition switch to the "ON" position, and check the voltage between AIV harness connector and ground. Battery voltage should be present. If okay, go to next step. If not, check power source to the ECU, and the harness between EFI relay and the solenoid valve.
- Check harness. Place a jumper wire between valve harness connector and ground. Measure resistance between the solenoid valve and ECU 20-pin connector terminal No. 14. Resistance should be zero ohms. If not, repair/replace harness as needed. If okay, replace ECU.