Isuzu N-Series. Manual — part 450
6E-136 EMISSION AND ELECTRICAL DIAGNOSIS
Working Check
Apply powervoltage between the terminals, there
is no problem if the negative pressure does not rise
when applied to the input port.
Caution:
When measuring resistance with a circuit tester, be
careful not to damage or deform the terminals.
N6A1266E
EMISSION AND ELECTRICAL DIAGNOSIS 6E-137
Aneroid Compensator Malfunction
N6A1267E
6E-138 EMISSION AND ELECTRICAL DIAGNOSIS
Inspection
1. Thermosensor (Engine coolant temperature
(ECT))
Soak the temperature sensitive part of a ther-
mosensor in the water, and while changing the wa-
ter temperature, make sure the resistance is
changed as the following graph shows:
2. Vacuum Switching Valve (VSV)
Resistance Check
Check the resistance between the VSV connector
terminals using a circuit tester.
Cold Resistance
: 37 — 44 (
Ω) (for 12 Volt)
: 159 — 169 (
Ω) (for 24 Volt)
Connect battery voltage between VSV connector
terminals and make sure of the continuity between
the pots.
Airtight Check
Apply negative pressure to the negative pressure
input port as illustrated on the left.
Although there is leakage, it is no problem if the
negative pressure rises to -46.7 kPa (-350 mmHg /
-6.77 psi) or more.
Legend
1. Resistance (k
Ω)
2. ECT
°F (°C)
N6A1254E
N6A1255E
Legend
1. 2 Pin
2. Port
N6A1264E
N6A1265E
EMISSION AND ELECTRICAL DIAGNOSIS 6E-139
Working Check
Apply powervoltage between the terminals, there
is no problem if the negative pressure does not rise
when applied to the input port.
Caution:
When measuring resistance with a circuit tester, be
careful not to damage or deform the terminals.
3. Actuator
Diaphragm is built in the actuator, by which the in-
side of the actuator is divided into two, atmospheric
room and negative pressure room.
4. Aneroid compensator Actuator
The link of the actuator for the aneroid compensa-
tor is connected to full load set lever.
The full load set lever is connected to a U-lever.
When the atmospheric sensor built in Engine Con-
trol Module (ECM) makes the actuator work, the
full load set lever and U-lever are rotated to a spec-
ified position so that the control rack is drawn in the
direction of reducing fuel injection amount.
Legend
1. Vacuum chamber
2. Atmospheric chamber
3. Diaphragm
N6A1266E
N6A1273E
Legend
1. Aneroid compensator actuator
2. Full load set lever
N6A1274E
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