Service Manual Owner's manual

SECTION 3 - CHASSIS & TURNTABLE
3-124 – JLG Lift – 3121139
ELECTROSTATIC DISCHARGE DAMAGE
Electronic components used in the ECM are often
designed to carry very low voltage. Electronic compo-
nents are susceptible to damage caused by electrostatic
discharge. Less than 100 volts of static electricity can
cause damage to some electronic components. By com-
parison, It takes as much as 4000 volts for a person to feel
the spark of a static discharge.
There are several ways for a person to become statically
charged. The most common methods of charging are by
friction and induction.
An example of charging by friction is a person sliding
across a seat.
Charge by induction occurs when a person with well-insu-
lated shoes stands near a highly charged object and
momentarily touches ground. Charges of the same polar-
ity are drained off, leaving the person highly charged with
the opposite polarity. Static charges can cause damage,
therefore it is important to-use care when handling and
testing electronic components.
To prevent possible electrostatic discharge damage, fol-
low these guidelines:
• Do not touch the ECM connector pins or soldered
components on the ECM board.
• Do not open the replacement part package until the
part is ready to be installed.
• Before removing the part from the package, ground
the package to a known good ground on the equip-
ment.
• If the part has been handled while sliding across a
seat, while sitting down from a standing position, or
while walking a distance, touch a known good ground
before installing the part.
Fuel System
FUEL INJECTOR
The Electronic Fuel Injection (EFI) fuel injector is a sole-
noid-operated device controlled by the ECM. The ECM
energizes the solenoid, which opens a valve to allow fuel
delivery.
The fuel is injected under pressure in a conical spray pat-
tern at the opening of the intake valve. Excess fuel not
used by the injectors passes through the fuel pressure
regulator before being returned to the fuel tank.
A fuel injector which is stuck partly open will cause a loss
of fuel pressure after the engine is shut down, causing
long crank times.
FUEL METERING SYSTEM COMPONENTS
The fuel metering system is made up of the following
parts:
•The fuel injectors
•The fuel rail
• The fuel pressure regulator/filter assembly
• The electronic governor
•The ECM
• The crankshaft position (CKP) sensor
• The camshaft position (CMP) sensor
•The fuel pump
• The fuel pump relay
BASIC SYSTEM OPERATION
The fuel metering system starts with the fuel in the fuel
tank. The fuel is drawn up to the fuel pump through a pre-
filter. The electric fuel pump then delivers the fuel to the
fuel rail through an inane fuel filter. The pump is designed
to provide fuel at a pressure above the pressure needed
by the injectors. A fuel pressure regulator in the fuel filter
assembly keeps fuel available to the fuel injectors at a
constant pressure. A return line delivers unused fuel back
to the tank.