Isuzu engine 4j series. Service manual - part 92
QOSII PREHEATING SYSTEM 6D6 – 5
Condition
Cause
Circuit
Through glow plug
relay turns ON,
preheating is not
done.
Bad connection of FLW between battery and glow relay.
Bad connection or disconnection in preheating circuit of glow relay main contact
terminal connector.
Bad connection between plug connector and preheating circuit
1
9
Glow plug relay
turns ON, but does
not go OFF.
Bad timer.
Bad timer. Short circuiting in circuit or earth between 5 terminal and glow relay.
Bad glow relay.
6
Indication lamp is
not lit.
Bad timer.
Burning-out of light bulb.
8
Note: Circuit No. in rectangle is shown in the previous pre-heating chart.
2) Problems when the time water temperature of the engine is 0°C or above.
Condition
Cause
Circuit
Indicator lamp is
not lit
Bad timer
Burning-out of bulb.
8
Turn glow relay
ON.
Bad thermoswitch or disconnection of thermo SW circuit.
(Indicator will light up for 3.5 seconds.)
Bad timer.
Bad timer. Short-circuiting in circuit or earth between terminals 5 and glow relay.
4
Note: Circuit No. in rectangle is shown in the previous pre-heating chart.
3) Burning-out of glow plug
When only one line is burned out, it has no effect on the start up of the engine. Even if one line is burned
out, judging from the characteristics of the glow plug, the impressed voltage will change only slightly.
Therefore, no judgment can be made by normal testing while the glow plug is installed. In order to check
for disconnections and burn-outs, the glow plugs will have to be removed from the connectors and checked
one by one for continuity.