Isuzu N-Series. Service manual — part 543
6F-2 Exhaust System
EGR System
Service Precautions
Perform EGR related assembly according to the usual
procedure of temporarily fitting and then permanently
tightening the parts so that unnecessary stresses are
not applied on the parts.
Explanations on Functions and Operation
The EGR system recirculates a part of exhaust gas
back into the intake manifold, which results in reducing
nitrogen oxide (NOx) emissions. The EGR control
system uses an electronic control system to ensure
both driveability and low emission. The control current
from the engine control module (ECM) operates the
motor to control the lift amount of EGR valve. Also, an
EGR position sensor is provided at the rear of the
motor to feed actual valve lift amount back to the ECM
for more precision control of the EGR amount.
The EGR control starts when the conditions for engine
speed, engine coolant temperature and barometric
pressure are satisfied. Then, the valve opening is
calculated according to the engine speed, and target
fuel injection quantity. Based on this valve opening, the
drive duty of the motor is determined and the motor is
driven accordingly.
A potentiometer type EGR valve position sensor is
employed and installed on the EGR valve body. The
EGR valve position sensor is supplied with reference
voltage (5V) and ground at all times from the ECM. The
ECM reads the EGR position sensor voltage input and
determines the EGR lift position.
Legend
1. EGR Cooler
2. ECM
3. EGR Valve
1
2
3
N6A6659E
Exhaust System 6F-3
EGR Valve and EGR Cooler
Components
Legend
1. EGR Pipe
2. EGR Cooler
3. EGR Adapter
4. EGR Valve
5. Cooling Water Pipe (IN)
6. Cooling Water Pipe (OUT)
Removal
1. Drain engine coolant. Refer to Engine Cooling
System section.
2. Remove the EGR valve connector.
N6A6432E
6F-4 Exhaust System
3. Remove the EGR pipe.
Legend
1. EGR Adapter
2. Water Return Pipe
3. EGR Cooler
4. EGR Pipe
5. Water Feed Pipe
4. Remove the cooling water pipes.
5. Remove the EGR adapter.
6. Remove the EGR cooler.
7. Remove the EGR valve.
Caution:
After removing the EGR valve and EGR adapter, seal
the opening so that foreign matter does not enter.
Inspection
• Gas leak check
- Check for gas leak in various parts of the EGR
gas line.
If the results of the check show abnormalities,
repair or replace the defective parts.
• EGR valve check
Installation
1. Mount the EGR valve.
• Insert the gasket and temporarily fit the EGR
valve.
Notice:
Temporarily tighten the bolts.
2. Install the EGR cooler.
• Temporarily fit the EGR cooler to the bracket.
Notice:
Temporarily tighten the bolts.
3. Install the EGR adapter.
• Temporarily fit the EGR adapter between the
EGR cooler and exhaust manifold.
Notice:
Temporarily tighten the bolts.
4. Install the EGR pipe.
• Insert the gasket between the two ends of the
EGR pipe and temporarily fit it.
Notice:
Temporarily tighten the bolts.
N6A6025E
N6A6491E
Exhaust System 6F-5
During temporary assembly, tighten the nuts
and bolts to the specified torque in the order
shown in the illustration.
Tighten:
Bolts and nuts to
(1): 31 N
⋅m (3.2 kg⋅m/23 lb⋅ft)
(2), (4): 28 N
⋅m (2.9 kg⋅m/21 lb⋅ft)
(3), (5), (6), (7), (8), (9): 24 N
⋅m (2.4 kg⋅m/17 lb⋅ft)
N6A6433E
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