Air injection system problems can cause engine backfiring (loud popping sound), other noises, and increased HC and CO emissions. Remember, air injection is used to help burn any fuel that enters the exhaust manifolds and exhaust system. Inadequate air from the air injection system also prevents the catalytic converter from functioning properly.
Air injection system maintenance
Maintenance of an air injection system typically includes replacing the pump inlet filter (if used), adjusting pump belt tension, and inspecting the condition of the hoses and lines
If the pump belt or any hoses show signs of deterioration, they should be replaced. Refer to service manual specifications for maintenance intervals.
Testing air injection system
A four-gas exhaust analyser provides a quick and easy method of testing an air injection system. Run the engine at idles and record the readings. Then, disable the air injection system. Remove the air pump belt or use pliers to pinch the hoses to the air distribution manifold. Compare the exhaust analyser readings before and after disabling the air injection system.
Without air injection, the exhaust analyser O2 reading should drop approximately 2-5 percent. HC and CO readings should increase. This would show that the air injection system is forcing air (oxygen) into the exhaust system.
If the analyser readings do NOT change, the air injection system is not functioning. Test each component until the source of the problem is found.
To test the air pump, remove the output line from the pump~ as in Fig. 32-9. Measure the amount of ‘pressure developed by the pump at idle. Typically, an air pump should produce about 15 to 20 kPa of pressure. If a low pressure gauge is not available, place your finger over the line and check for pressure. Replace the pump if faulty.
To test the diverter valve or other air injection system valves, use a service manual. It will explain testing procedures for the specific components.