Isuzu engine 4j series. Manual - part 93

QOSIII PREHEATING SYSTEM  6D7 – 3

QOS III FLOW CHART

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6D7 – 4  QOSIII PREHEATING SYSTEM

QOS III BLOCK CHART

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QOSIII PREHEATING SYSTEM  6D7 – 5

Inspection on QOSIII System Operation

I

Inspection on Quick Heating Operation

1. Disconnect thermo-sensor connection on the

thermostat housing.

2. Connect the circuit tester between glow plug and

engine earth.

3. Inspect the following items with starter switch set to

ON position (but do not start the engine).

1) The glow indicator shall light for 1 ~ 6 sec.
2) The circuit tester shall indicate power supply voltage

for 9 ~ 13 sec.

•

If above specifications are not satisfied, inspect wire
harness, glow relay and thermo-sensor.  If satisfied,
inspect glow plug.

II

Inspection on Quick Heating Afterglow Operation

1. Disconnect thermo-sensor connection on the

thermostat housing.

2. Connect the circuit tester between glow plug and

engine earth.

3. Inspect the following item with start the engine.
1) The circuit tester shall indicate power supply voltage

for about 5 seconds.

•

If above specification is not satisfied, inspect battery
voltage, engine earth, wire harness and starter switch
"st" signal to control unit.
If satisfied, inspect wiring harness, engine earth and
starter switch.

III Inspection on Afterglow Operation
1. Disconnect thermo-sensor connection on the

thermostat housing.

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6D7 – 6  QOSIII PREHEATING SYSTEM

2. Connect the circuit tester between glow plug and

engine earth.

3. Inspect the following items with start the engine.
1) The circuit tester shall indicate about 7 volts after 360

seconds of engine start.

•

If above specifications are not satisfied, inspect battery
voltage, engine earth, wiring harness, glow plug,
dropping resistor, relay No. 2 and charge relay.

THERMO SENSOR

Measure the resistance depending on the water
temperature as shown in the left figure.  (Measuring range:
10°C ~ 50°C)

Temperature

Current (mA)

Resistance (KW)

20 ± 1

1.0

2.0 ~ 3.0

50 ± 1

1.0

0.68 ~ 1.0

When installing the thermo sensor, apply sealant (Loctite
#262 or equivalent) to narrowed portion in the left figure to
prevent water leakage
Torque

N∙m (kg∙m/lb∙in)

                                                                                                                   

8 (0.8/69)

                                                                                                                   

GLOW PLUG

Inspect the resistance

Resistance at normal temperature

Ω

                                                                                                                   

0.8 ~ 1.0

                                                                                                                   

Torque

N∙m (kg∙m/lb∙ft)

                                                                                                                   

23 (2.3/17)

                                                                                                                   

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