Isuzu engine 4j series. Instruction - page 91
QOSII PREHEATING SYSTEM 6D6 – 1
SECTION 6D6
QOSII PREHEATING SYSTEM
(4JB1/4JB1T/4JB1TC ONLY)
CONTENTS
PAGE
General Description....................................................................................................... 6D6 - 1
System Diagram............................................................................................................. 6D6 - 2
Inspection on QOS II system Operation ...................................................................... 6D6 - 3
QOSII System Troubleshooting.................................................................................... 6D6 - 4
GENERAL DESCRIPTION
QOS II preheating system features a quick-on glow
plug with thermometer control of the glowing time and
the afterglow time function.
The system consists of a controller, indicator lamp,
thermoswitch, relay, and glow plug ( 4 pcs).
With the employment of the thermoswitch, the glow
time changes according to the engine coolant
temperature, thus allowing optimum starting conditions
to be obtained.
6D6 – 2 QOSII PREHEATING SYSTEM
SYSTEM DIAGRAM
QOS II Timing Chart
6D6-2-1.tif
6D6-2-2.tif
QOSII PREHEATING SYSTEM 6D6 – 3
Inspection on QOSII System Operation
THERMO SWITCH
The thermo switch is located on the water outlet pipe.
Use a circuit tester to check the thermo switch for continuity.
OFF
!ON
: 7-13°C (44.6-55.4°F)
ON
!OFF
: Below 3°C (37.4°F)
10°C
ON
OFF
3°C
GLOW PLUG
Use a circuit tester to test the glow plugs for continuity.
Glow Plug Resistance (Reference)
Ohms
Conventional model
Approximately 1.5
Quick on start model
Approximately 0.9
6D6-3-1.tif
6D6-3-2.tif
6D6-3-3.tif
6D6 – 4 QOSII PREHEATING SYSTEM
QOSII SYSTEM TROUBLESHOOTING
Problems when the water temperature of the engine is 0°C below.
Condition
Cause
Circuit
Glow plug relay will
not be lit.
Bad connection of FLW between battery and starter.
Bad connection or disconnection of starter SW circuit
Bad connection or disconnection
Malfunction of other
of Fuse No . 8
circuits occurred
simultaneously.
Bad starter awitch.
Bad connection of glow plug relay terminal.
Disconnection of glow plug relay excitation coil.
Disconnection of circuit between glow plug relay and timer.
Bad glow relay. (The main contact does not pass electricity.)
Bad connection of timer.
Bad timer.
Bad earth circuit of timer.
Bad thermoswitch. (It remains ON even in water temperature below 0°C.)
Earth short-circuiting of thermo SW.
3
2
1
6
7
7
6D6-4-1.tif