JLG 340AJ, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3121259 – JLG Lift – 3-81
3.18 GM DUAL FUEL ENGINE
Unlike the Kubota engine, the GM Dual Fuel engine is con-
trolled by its own Electronic Control Unit (ECU). The engine
uses gasoline as its primary fuel, but can also be switched to
run on Liquid Propane (LP) as an alternate fuel. This fuel selec-
tion is made by the operator at the machine platform control.
The Platform Control Module communicates this selection to
the ECU which controls the transition between the two fuels.
Communications with the JLG Control System
The JLG Control System communicates with the GM engine by
sending the following control messages from the Ground
Module to the engine’s ECU:
• Fuel Type and Engine Start
• Engine Speed Request
• Engine Shutdown Request
The engine’s ECU sends the following communications to the
Ground Module:
• Engine RPM
• Engine Oil Pressure
• Engine Coolant Temperature
Engine Start
The Ground Module energizes terminal J1-11 to engage the
starter. The engine ECU considers the engine started when
RPMs are greater than 800 and continues in the Run mode
unless engine RPM drops below 200. The ECU establishes a
maximum crank time of 7.5 seconds before a 20 second wait
time is required. The ECU also requires that power is cycled
after 60 seconds of cranking time.
Oil Pressure
The Ground Module calculates the engine oil pressure based
on information sent to it by the engine ECU.
Engine Speed
The Ground Module calculates the engine RPM based on infor-
mation sent to it by the engine ECU.
Coolant Temperature
The Ground Module calculates the engine coolant tempera-
ture based on information sent to it by the engine ECU.
Fuel Select
If the Fuel Select input J1-33 on the Platform Module is ener-
gized, the Ground Module communicates to the ECU that the
engine should be calibrated for LP fuel. If the Fuel Select input
J1-33 on the Platform Module is not energized, the Ground
Module communicates to the ECU that the engine should be
calibrated for gasoline.