Dodge RAM TRUCK 1500 1995 Service Manual page 1715

EMISSION CONTROL SYSTEMS 25 -17
Refer to the Air Pump Diagnosis chart for addi­
tional information.
Refer to the Component Removal/Installation sec­
tion of this group for air pump replacement proce­
dures.
ONE-WAY CHECK VALVE
A check valve, (Fig. 23) is located on each of the air
injection downstream tubes.
Each check valve has a one-way diaphragm which
prevents hot exhaust gases from backing up into the
hose and pump. The check valve will protect the sys­
tem if the air injection pump belt fails, an air hose
ruptures or exhaust system pressure becomes abnor­
mally high.
TESTING CHECK WALWE
The one-way check valves are not repairable. To de­
termine condition of valve, remove the rubber air
tube from the inlet side of each check valve. Start the
engine. If exhaust gas is escaping through the inlet
side of check valve, it must be replaced.
Refer to the Component Removal/Installation sec­
tion of this group for check valve replacement proce­
dures.
AIR PUMP DIAGNOSIS
CONDITION
POSSIBLE CAUSES
CORRECTION
E X C E S S I V E BELT NOISE
1. Loose belt or defective auto,
belt tensioner.
2. Seized pump.
1. Refer to Group 7, Cooling.
2. Replace pump.
E X C E S S I V E PUMP NOISE
CHIRPING
1. Insufficient break-in.
1. Recheck for noise after 1600 km. (1,000
miles) of operation.
E X C E S S I V E PUMP NOISE
CHIRPING, RUMBLING, OR
KNOCKING
1. Leak in hose.
2. Loose hose.
3. Hose touching other engine parts.
4. Relief valve inoperative.
5. Check valve inoperative.
6. Pump mounting fasteners loose.
7. Pump failure.
1. Locate source of leak using soap solution
and correct.
2. Reassemble and replace or tighten hose
. clamp.
3. Adjust hose position.
4. Replace relief valve.
5. Replace check valve.
6. Tighten mounting screws as specified.
7. Replace pump.
NO AIR S U P P L Y (ACCEL­
ERATE ENGINE TO 1500
RPM AND O B S E R V E AIR
FLOW FROM HOSES). IF
THE FLOW INCREASES AS
THE RPM'S INCREASE, THE
PUMP IS FUNCTIONING
NORMALLY. IF NOT, CHECK
POSSIBLE CAUSE.
1. Loose drive belt.
2. Leaks in supply hose.
3. Leak at fitting(s).
4. Check valve inoperative.
5. Plugged inlet air filter (8.0L).
1. Refer to Group 7, Cooling.
2. Locate leak and repair or replace as
required.
3. Tighten or replace clamps.
4. Replace check valve.
5. Replace filter.
J9525-15