Air Injection: Testing and Inspection
AIR Management Diagnosis:
DFI Emission Circuit:
DIAGNOSIS Numbers below refer to circled numbers on the diagnostic chart.
1. With a cold engine, the air management system should switch air to the exhaust ports (the heads) to help oxidize the rich mixture that exists during cold starts and warmup.
2. With a warm engine, the air should be switched to the converter to oxidize the exhaust gas flowing to the second bed of the catalytic converter.
3. Checking for the air system to "DIVERT" air away from the converter during acceleration and deceleration. The divert function protects the converter from the following rich conditions that occur:
A. During acceleration.
B. During power enrichment.
C. When the throttle is closed to start deceleration.
4. Checking for vacuum supply to the air management valves.
5. Checking for air pump operating.
6. This branch of the tree will check for ECM ability to control air switch and air divert solenoids.
7. Checking for open or voltage to the solenoid.
8. Checking for a low resistance solenoid. If resistance is less than 20 ohms, replace the air management solenoid.
CIRCUIT DESCRIPTION
The AIR divert and switch solenoids are supplied with 12 volts on circuit 639 from the 10 amp number 5 solenoid fuse on the underhood relay panel. The ECM controls air management by grounding AIR switch solenoid circuit 436 and AIR divert solenoid circuit 429. To divert air to the air cleaner, the divert solenoid is de-energized. When pin C4 at the ECM is grounded, the divert solenoid energizes and diverts air to the switching valve. When the switch solenoid is de-energized the air is routed to the catalytic converter and when pin D3 at the ECM is grounded the air is routed to the exhaust ports.
AIR PUMP DIAGNOSIS
The air pump is a positive displacement vane type which is permanently lubricated and requires no periodic maintenance. DO NOT OIL AIR PUMP! The AIR system is not completely noiseless. Under normal conditions, noise rises in pitch as engine speed increases.
Accelerate engine from idle to approximately 1500 RPM and observe air flow from the hose(s). If air flow increases as engine is accelerated, the pump is operating satisfactorily. If air flow does not increase or is not present, proceed as follows:
1. Inspect for proper drive belt tension.
2. Inspect for a leaky pressure relief valve. Air may be heard leaking with the pump running.
3. Inspect for a seized air injection pump.
4. Inspect hoses, tubes and all connections for leaks and proper routing.
5. Inspect for air flow from control/switching valve.
6. Inspect air injection pump for proper mountion and bolt torque.
7. If no irregularities exist and the air injection pump noise is still excessive, remove and replace pump.
CHECK VALVE DIAGNOSIS
The check valve should be inspected whenever the hose is disconnected from it or whenever check valve failure is suspected (a pump that had become inoperative and had shown indications of having exhaust gases in the pump would indicate check valve failure). Remove check valve and blow through it, (toward the cylinder head) then attempt to suck back through the check valve. Flow should only be in one direction (toward the cylinder head). Replace the valve if there is flow in both directions.
1. Inspect the hose or pipe for deterioration or holes.
2. Inspect all hoses or pipe connections, and clamp tightness.
3. Inspect hose or pipe routing. Interference of routing may cause wear.
4. If a leak is suspected on the pressure side of the system or if a hose or pipe has been disconnected on the pressure side, the connections should be checked for leaks with a soapy water solution. With the pump running, bubbles will form if a leak exists.