Air Injection: Description and Operation

Fig.1 Air Injection System Components - Typical:

Fig.2 Air Inlet For Air Pump - 5.9L HDC Engine:

Fig.3 Air Inlet And Air Pump Air:

AIR INJECTION
Air Injection System
The air injection system, or is used on 5.9L V-8 and 8.0L V-10 Heavy Duty Cycle (HDC) gas powered engines only. The air injection system consists of:
- A belt-driven air injection (AIR) pump
- Two air pressure relief valves
- Rubber connecting air injection hoses with clamps
- Metal connecting air tubes
- Two one-way check valves
- A replaceable injection pump air filter (8.0L V-10 engine only)

The air injection system adds a controlled amount of air to the exhaust gases aiding oxidation of hydrocarbons and carbon monoxide in the exhaust stream. The system does not interfere with the ability of the EGR system (if used) to control Nitrous Oxide (NOx) emissions.

5.9L HDC Engine: Air is drawn into the pump through a rubber tube that is connected to a fitting on the air cleaner housing.

8.0L V-10 Engine: Air is drawn into the pump through a rubber tube that is connected to a fitting on the air injection pump filter housing. Air is drawn into the filter housing from the front of the vehicle with rubber tube. This tube is used as a silencer to help prevent air intake noise at the opening to the pump filter housing. An air filter is located within the air pump filter housing.

Air is then compressed by the air injector pump. It is expelled from the pump and routed into a rubber tube where it reaches the air pressure relief valve. Pressure relief holes in the relief valve will prevent excess downstream pressure. If excess downstream pressure occurs at the relief valve, it will be vented into the atmosphere.

Air is then routed from the relief valve, through a tube, down to a Y connector, through the two one-way check valves and injected at both of the catalytic convertors (referred to as downstream).

The two one-way check valves protect the hoses, air pump and injection tubes from hot exhaust gases backing up into the system. Air is allowed to flow through these valves in one direction only (towards the catalytic convertors).

Downstream air flow assists the oxidation process in the catalyst, but does not interfere with EGR operation (if EGR system is used).

Fig.4 Air Injection Pump Mounting - Typical:

AIR INJECTION PUMP
The air pump is mounted on the front of the engine and driven by a belt connected to the crankshaft pulley.
Refer to Air Injection System Description and Operation for information.

ONE WAY CHECK VALVE
For air injection Systems: A pair of one-way check valves is used with the air injection system. The check valves are located on each of the air injection downstream tubes.

Each one-way check valve has a one-way diaphragm which prevents hot exhaust gases from backing up into the air injection hose and air injection pump. The check valve will protect the system if the air injection pump belt fails, an air hose ruptures or exhaust system pressure becomes abnormally high.