Isuzu NHR 4J Series Workshop Manual page 372

Condition
Through glow plug Bad connection of FLW between battery and glow relay.
relay turns ON,
Bad connection or disconnection in preheating circuit of glow relay main contact
preheating is not
terminal connector.
done.
Bad connection between plug connector and preheating circuit
Glow plug relay Bad timer.
turns ON, but does
Bad timer. Short circuiting in circuit or earth between 5 terminal and glow relay.
not go OFF.
Bad glow relay.
Indication lamp is Bad timer.
not lit.
Burning-out of light bulb.
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
Indicator lamp is Bad timer
not lit
Burning-out of bulb.
Turn glow relay Bad thermoswitch or disconnection of thermo SW circuit.
ON. (Indicator will light up for 3.5 seconds.)
Bad timer.
Bad timer. Short-circuiting in circuit or earth between terminals 5 and glow relay.
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.
QOSII PREHEATING SYSTEM 6D6 – 5
Cause
Cause
Circuit
1
9
6
8
Circuit
8
4