JLG 740AJ, Руководство по обслуживанию и ремонту

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SECTION 3 - CHASSIS & TURNTABLE
3121160 3-155
ELECTROSTATIC DISCHARGE DAMAGE
Electronic components used in the Engine Module are often
designed to carry very low voltage. Electronic components are
susceptible to damage caused by electrostatic discharge. Less
than 100 volts of static electricity can cause damage to some
electronic components. By comparison, 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 fric-
tion and induction.
An example of charging by friction is a person sliding across a
seat.
Charge by induction occurs when a person with well-insulated
shoes stands near a highly charged object and momentarily
touches ground. Charges of the same polarity 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, follow
these guidelines:
• Do not touch the Engine Module connector pins or sol-
dered components on the Engine Module 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 equipment.
• If the part has been handled while sliding across a seat,
while sitting down from a standing position, or while walk-
ing a distance, touch a known good ground before install-
ing the part.
Fuel System
FUEL INJECTOR
The Electronic Fuel Injection (EFI) fuel injector is a solenoid-
operated device controlled by the Engine Module. The Engine
Module energizes the solenoid, which opens a valve to allow
fuel delivery.
The fuel is injected under pressure in a conical spray pattern 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 Engine Module
• 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.