Chrysler DODGE D150 1993 Service Manual page 1492

• EMISSION CONTROL SYSTEMS 25 - 15
A I R I N J E C T I O N S Y S T E M — 5 . 9 L H D C - G A S E N G I N E
INDEX
page
Air Injection Pump 15
Check Valve—Air Injection Tube 16
General Information
page
. . 15
GENERAL INFORMATION
The air injection system (Fig. 1) is used on the 5.9L
(V-8) heavy duty cycle (HDC) gas powered engines
only. The air injection system consists of:
• A belt-driven air injection pump
• An air relief valve
• Rubber hoses and check valves
The check valves (Fig. 1) protect the hoses and in­
jection tubes from hot exhaust gases.
The air injection system adds a controlled amount
of air to the exhaust gases aiding oxidation of hydro­
carbons and carbon monoxide in the exhaust stream.
The system does not interfere with the ability of the
EGR system to control nitrous oxide (NOx) emis­
sions.
Outside air is drawn into the front of the air injec­
tion pump (Fig. 2) where it is compressed and ex­
pelled into the relief valve (also refer to Air Injection
Pump in this group for additional information). Pres­
sure relief holes in the air relief valve (Fig. 2) will
prevent excess downstream pressure.
Air is injected at both of the catalytic convertors
(referred to as downstream). All injected air is routed
by the air relief valve (Figs. 1 or 2).
Downstream air flow assists the oxidation process
in the catalyst, but does not interfere with EGR op­
eration.
AIR INJECTION PUMP
The air pump is mounted on the front of the engine
and driven by a belt connected to the crankshaft pul­
ley (Fig. 1 or 2). Intake air passes through a fan at
the front of the pump. Foreign materials are sepa­
rated from the air by centrifugal force. Air is then
delivered to the air relief valve.
The air injection system is not completely
noiseless. Under normal conditions, noise rises in
pitch as engine speed increases. To determine if ex-
HOSE
TEE
CATALYTIC
CONVERTORS (2)
AIR
PUMP
RELIEF
VALVE
GASKET
J9325-35
Fig. 1 Air injection System Components—5.9L Heavy Duty Cycle Engine