JLG 450A_AJ Series II Service Manual - Manual (Page 173)

SECTION 3 - CHASSIS & TURNTABLE
3121180 – JLG Lift – 3-123
EPR Assembly
The EPR assembly is a combination Low Pressure Regu-
lator and a Voice Coil Assembly. The Voice coil is an elec-
tronic actuator controlled by an internal microprocessor.
The microprocessor provides output data to the ECM and
receives input data over a CAN BUS connection. The
internal microprocessor receives electrical signals from
the Fuel Pressure Sensor FPS and the Fuel Temperature
Pressure FTP and communicates the data to the ECM.
The ECM uses FPS and FTP data to calculate location of
the secondary lever in the LPR and sends that data back
to the EPR via the CAN BUS. The internal microprocessor
in the EPR will then output a signal, which causes the
voice coil to move and position the secondary lever to the
correct location.
Low Pressure Regulator (LPR)
The LPR is a combination vaporizer, pressure regulating
device. The LPR is a negative pressure, two stage regula-
tor that is normally closed when the engine is not running.
When the engine is cranking or running, a partial vacuum
is created in the fuel line which connects the regulator to
the mixer. This partial vacuum opens the regulator permit-
ting fuel to flow to the mixer.
Propane fuel enters the primary port of the LPR and
passes through the primary jet and into the primary/
exchanger chamber. As propane passes through the heat
exchanger, the fuel expands and creates pressure inside
the chamber. Pressure rises as fuel expands when pres-
sure rises above 1.5 psi (10.34 kpa), sufficient pressure is
exerted on the primary diaphragm to cause the dia-
phragm plate to pivot and press against the primary valve
pin thus closing off the flow of fuel. This action causes the
flow of fuel into the regulator to be regulated.
When engine is cranking, sufficient vacuum will be intro-
duced into the secondary chamber from the mixer draw-
ing the secondary diaphragm down onto the spring
loaded lever and opening the secondary valve allowing
vaporized fuel to pass to the mixer. This mechanical action
in conjunction with the EPR reactions causes the down-
ward action on the secondary lever causing it to open
wider allowing more fuel to flow to the mixer.
VOICE COIL SECTION OF EPR ASSEMBLY IS AN EMISSIONS
CONTROL DEVICE AND CANNOT BE REBUILT. IF COIL ASSEM-
BLY FAILS TO OPERATE PROPERLY, REPLACE WITH AN OEM
REPLACEMENT PART ONLY.
1. Pressure Regulator Section
2. Fuel Inlet
3. Coolant Passage 4. Primary Test Port
5. Secondary Test Port
6. Voice Coil Section
Figure 3-78. EPR Assembly
Figure 3-79. Low Pressure Regulators