automobile car air system injection PRACTICAL AIM: Air Injection system service. THEORY:
Pulse air injection system is used to inject fresh air into exhaust system. When fresh air is injected into hot exhaust gases,combustion takes place. This reduces amount of unburned fuel that escapes into the atmosphere. System consists of check valves, control valves, control valve solenoids, vacuum reservoir, vacuum lines and air lines. Pulse air system is capable of injecting air at both catalytic converter(downstream) or at front exhaust pipe. Emission test failureComponents
– Air pump
– Check valve
– Diverter valve
– Air-switching valve
Look for rusty check valves and air manifolds
Check condition of hoses mounted near exhaust parts
Inspect air pump drive belt
Several problems in an air injection system:
Exhaust noise under the hood
Backfiring on deceleration
Air pump noisy or frozen
AIR System Testing:
Check condition of all hoses and lines in system. Reroute any kinked or restricted hoses. Repair or replace any cracked or broken hoses. To check system operation, feel for suction in injection hoses at air cleaner.
If problem exists, check to see if vacuum is being supplied to the valve. If vacuum is not present at valve(s), check vacuum lines or ports.
Check vacuum lines and AIR lines for cracks or improper connection (high heat lines must be high silicone rubber)
Check metal lines for rusting (especially connected to catalytic converter)
Unhook AIR line from check valve and see that exhaust is not coming out of the valve
Verify that AIR switching valve is working properly
– Open loop – upstream
– Closed loop – downstream
Connect vacuum pump to diverter valve and verify that it diverts the air to the air cleaner when vacuum exceeds specified limit
Forces fresh air into the exhaust ports or catalytic converter to reduce HC/CO.
Pulse air system uses alternating positive and negative pressure pulsations in exhaust system to draw in fresh air through air cleaner. Check valves are used to allow fresh air into exhaust,but prevent exhaust from flowing back into intake system.Air is switched between upstream and downstream injection by2 vacuum-operated control valves. Each control valve is switched byan electrically operated-vacuum solenoid.Vacuum solenoids are switched on and off by MCU according to engine operating conditions. Vacuum storage tank maintains vacuum supply to switching solenoids. [IMG]file:///C:/Users/HARDIK~1/AppData/Local/Temp/msohtmlclip1/01/clip_image002.jpg[/IMG] Startup:
The AIR system injects air into the exhaust manifold, this creates an “afterburner” effect and helps burn up HC and CO
The additional heat produced by the afterburning helps bring the O2 sensor and catalytic converter up to temperature more quickly
Closed loop operation
The AIR system injects air downstream of the O2 sensor
This prevents a false lean reading
This provides extra oxygen to the oxidizing catalyst
Prevents exhaust from flowing into the AIR pump
This valve determines whether the air will go to the air cleaner or the diverter valve
Under rapid deceleration this valve switches the air to the air cleaner.
Air switching valve:
Depending on closed/open loop status this valve will direct the air into either the exhaust manifolds or catalytic converter.