See Figures 1, 2, 3, 4, 5 and 6
The AIR system injects compressed air into the exhaust system, near the exhaust valves to aid in the continued burning of exhaust gases. The system reduces the carbon monoxide (CO) and hydrocarbon levels in the exhaust gas that would normally be released into the atmosphere by increasing the oxygen content in the exhaust. Increasing the oxygen content in the exhaust gas enhances burning very much like increasing the draft or flow in a fireplace. To do this the system employs an air injection pump, a diverter valve, a check valve, and a system of hoses and tubes necessary to carry the compressed air from the pump to the exhaust manifolds.
The diverter valve is used to bypass air away from the exhaust system when the engine is decelerating or operating at continuous high speeds. If the system was not able to divert air during deceleration, backfiring in the manifold would occur. The diverter valve is a vacuum operated valve on early models and in some later models particularly on California vehicles, an electric solenoid valve was used. The vacuum operated diverted valves have a vacuum line connected to the intake manifold or carburetor, as engine speed decreases intake manifold vacuum increases. The increased vacuum causes the valve to open and divert air away from the exhaust manifold. On the electrically operated valves the Engine Control Module (ECM) or a control module controls the valve operation by applying ground to the air diver solenoid terminal "B". Battery voltage is applied to the solenoid "A" terminal whenever the ignition is on. When the module applies ground, the solenoid energizes which causes the valve to direct air to the exhaust ports. The module operates the valve based on coolant temperature, engine speed and manifold vacuum. When the "CHECK ENGINE" light is on the module will turn the solenoid off which will result in air being diverted to the air cleaner. Check valves are also employed in the system to prevent the introduction of exhaust gases into the AIR systems plumbing and components.
To test the check valve, disconnect the hose at the diverter valve. Blow into the hose and then draw air from the hose. Be careful not to inhale any foreign substances during this procedure. Air should flow into the engine only.Diverter Valve
- Pull off the vacuum line to the top of the valve with the engine running. There should be vacuum in the line. Install the vacuum line and inspect. No air should be escaping with the engine running at a steady idle.
- Open and quickly close the throttle. A blast of air should come out of the valve muffler or air cleaner for at least one second.
- If the truck is equipped with a electric diverter valve go to the next Step. If not equipped with the electric type go to Step 6.
Disconnect the harness connector from the solenoid and then turn the ignition on. Connect a voltmeter or test light between terminal A on the harness connector and ground.
- If 10 volts or greater is measured or the test light lights, the solenoid is getting power.
- If less than 10 volts is measured or the test light does not light, the solenoid is not getting power due to an open or short to ground in the wiring.
- Measure the resistance across the solenoid by connecting an ohmmeter between the two terminals on the solenoid. Make sure that the solenoid is disconnected or a false reading may occur. The resistance of the solenoid should equal about 20 ohms.
- If the resistance is less than 20 ohms, the solenoid is shorted. Replace the solenoid and the Engine Control Module (ECM), as required.
- If the resistance is more than 20 ohms, the solenoid is open. Replace the solenoid.
- If the valve must be replaced, use a new gasket at the valve mounting on the pump and torque the bolts to 85 inch lbs. (9.5 Nm).
Disconnect the hose from the diverter valve. Start the engine and accelerate it to about 1,500 rpm. The airflows should increase as the engine is accelerated. If no airflow is noted or it remains constant, check the following:
- Inspect the drive belt tension and correct, if necessary.
- Listen for a leaking pressure relief valve. If it is defective, replace the relief/diverter valve assembly.
- Inspect for foreign matter in the pump filter openings. If the pump is defective or excessively noisy, it must be replaced.
The AIR system's effectiveness depends on correct engine idle speed and ignition timing. These settings should be strictly adhered to and checked frequently. All hoses and fittings should be inspected for condition and tightness of connections. Check the drive belt for wear and tension every 12 months or 12,000 miles. If, after completion of a tune-up and/or individual inspection of components, a malfunction still exists, the vehicle should be serviced by qualified mechanics.
The AIR system is not completely noiseless. Under normal conditions, noise rises in pitch as engine speed increases. To determine if excessive noise is the fault of the AIR system, operate the engine with the pump drive belt removed. If the noise does not exist with the belt removed:
- Check for a seized pump.
- Check hoses, tubes and connections for leaks or kinks.
- Check the diverter valve.
- Check the pump for proper mounting.
If no irregularities exist and the AIR pump noise is still excessive, replace the pump.
REMOVAL & INSTALLATION
See Figure 7
- Disconnect the air hoses at the pump.
- Hold the pump pulley from turning and loosen the pulley bolts.
- Loosen the pump mounting bolt and adjustment bracket bolt. Remove the drive belt.
- Remove the mounting bolts, and then remove the pump.
- Install the pump using a reverse of the removal procedure.
- Release the clamp and disconnect the air hoses from the valve.
- Unscrew the check valve from the air injection pipe.
- Installation is in the reverse order of removal.
- Remove the drive belt and pump pulley.
- Using needle nose pliers, pull the fan from the pump hub.
- To install a new filter, draw it on with the pulley and pulley bolts. Do not hammer or press the filter on the pump.
- Draw the filter down evenly by tightening the bolts alternately. Make sure the outer edge of the filter slips into the housing. A slight amount of interference with the housing bore is normal.
The new filter may squeal initially until the sealing lip on the pump outer diameter has worn in.Diverter (Anti-afterburn) Valve
- Turn the ignition off and disconnect the negative battery cable if vehicle is equipped with the electric solenoid valve.
- Detach the vacuum sensing line from the valve. Disconnect the wire harness connector if the valve is the electric type.
- Remove the other hose(s) from the valve.
- Unfasten the diverter valve from the elbow or the pump body.
- Installation is performed in the reverse order of removal. Always use a new gasket. Tighten the valve securing bolts to 85 inch lbs. (9.5 Nm).