Exhaust Emissions System - Air Injection System: Description

Two different types of air injection systems are used by Mercedes-Benz vehicles. Both systems reduce exhaust emissions by injecting fresh air into the cylinder head exhaust ports to aid in the combustion of exhaust gases. All Federal 450 models use a pulse-air type system that does not require an air pump. All other models use the conventional air pump type system. System components differ according to vehicle models and application.

On Federal 280 models, system consists of a belt-driven air pump, pressure relief valve, diverter valve, two check valves, and a thermo valve. On California 280 models, system consists of a belt-driven air pump, pressure relief valve, diverter valve, two check valves, and two thermo valves.

On Federal 450 models, the pulse-air type system consists of a check valve, fresh air hose (connecting check valve to air cleaner), air injection lines, and injection passages in the cylinder heads. See Figure. On California 450 and 6.9 models, system consists of a belt-driven air pump, diverter valve, 2 check valves and a thermo valve.