Glow Plugs - JLG H340AJ Service And Maintenance Manual

Glow Plugs

The diesel engine has two in-cylinder glow plugs to assist in
cold starting. The ground module controls the glow plugs and
uses a relay to switch battery current.
Ground Module
VBatt
J1-12
Figure 3-36. Engine Glow Plug Schematic
The Ground Module calculates the length of time the glow
plugs are energized prior to startup based upon ambient tem-
perature, engine coolant temperature, and battery voltage.
The machine control system monitors the engine coolant and
ambient temperature to make an estimate of cylinder preheat-
ing requirements. If the coolant temperature is below 50° C
(122° F) and the battery has sufficient voltage when control
power is turned on, the glow plugs will be automatically fired
for a duration that is based on the ambient temperature. Dur-
ing this preheat period, the glow plug indicators will flash. The
glow plugs will be turned off before the engine begins to
crank. Refer to Table 3-5, Glow Plug Conditions.
3121634
Engine
Coolant
Temperature
Greater than or
equal to
122 º F (50 º C)
Less than
Glow Plugs
122 º F (50 º C)
+
-
Less than
122 º F (50 º C)
Glow Plug Relay
Less than
122 º F (50 º C)
Less than
122 º F (50 º C)
SECTION 3 - CHASSIS & TURNTABLE
Table 3-5. Glow Plug Conditions
Battery Ambient
Voltage Temperature
- - - -
Less than
- - - -
11V
Greater than Greater than
11V 68ºF (20ºC)
Temp Between
Greater than
23ºF and 68ºF
11V
(-5ºC and 20ºC)
Temp Between
Greater than
5ºF and 23ºF
11V
(-15ºC and -5ºC)
Temp Less
Greater than
Than
11V
5ºF (-15ºC)
Pre-Glow Start/Run
Plug Glow Plug
State/Time State/Time
Off Off
Off Off
Engine State =
On for Cranking, Start-
20 sec. ing or Running:
On for 20 sec
Engine State =
On for Cranking, Start-
20 sec. ing or Running:
On for 20 sec
Engine State =
On for Cranking, Start-
20 sec. ing or Running:
On for 20 sec
Engine State =
On for Cranking, Start-
20 sec. ing or Running:
On for 20 sec
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