JLG 660SJ Service Manual - Manual (Page 116)

SECTION 3 - CHASSIS & TURNTABLE
3-66 – JLG Lift – 3121202
FUEL METERING SYSTEM PURPOSE
The basic function of the air/fuel metering system is to
control the air/fuel delivery to the engine. Fuel is delivered
to the engine by individual fuel injectors mounted in the
intake manifold near each intake valve.
The main control sensor is the heated oxygen sensor
(H02S) located in the exhaust system. The H02S tells the
ECM/EPM how much oxygen is in the exhaust gas. The
ECM/EPM changes the air/fuel ratio to the engine by con-
trol-ling the amount of time that the fuel injector is "ON."
The best mixture to minimize exhaust emissions is 14.7
parts of air to 1 part of gasoline by weight, which provides
the most efficient combustion. Because of the constant
measuring and adjusting of the air/fuel ratio, the fuel injec-
tion system is called a "closed loop" system.
The ECM/EPM monitors signals from several sensors in
order to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called "modes."
All modes are controlled by the ECM/EPM. Refer to "Open
Loop and Closed Loop Operation" for more information.
Figure 3-53. Typical Fuel System
HIGH PRESSURE CIRCUIT - OPERATING PRESSURE 65 PSI.