Gasoline Fuel Pump; Gasoline Pressure And Temperature Sensor Manifold; Fuel Filter; Fuel Injector Rail - JLG 400S Service And Maintenance Manual

Gasoline Fuel Pump

The Gasoline is stored as a liquid in the fuel tank and in drawn
into the fuel system by an electric fuel pump. The fuel pump
will receive a signal from the ECM to prime the fuel system for
approximately 2 seconds prior to start. Priming of the fuel sys-
tem provides for a quicker start, when the engine begins to
crank.
Gasoline Pressure And Temperature Sensor
Manifold
This engine is equipped with a fuel injector rail that does not
have a pressure regulator or a return circuit to the fuel tank.
Fuel pressure for this engine is regulated by the engine's ECM.
The ECM receive fuel pressure and temperature feedback from
the gasoline fuel sensor manifold and uses this information to
control the ground side of the fuel pump. Fuel pressure is reg-
ulated by the ECM pulse width modulating (PWM) the fuel
pump. The fuel pressure and temperature sensor manifold has
a return or "bleed" circuit that connects back to the fuel tank.
This circuit is used to bleed off any vapor that develops in the
line and return a small amount of fuel to the tank. The fuel
comes from the fuel tank and passes through the fuel pump.
Fuel exits the fuel pump, passes through the filter and then
enters the fuel pressure and temperature manifold assembly.
Fuel flows through the feed circuit and is delivered to the fuel
injector rail. Fuel that enters the bleed circuits through they
bypass valve in the manifold is returned to the fuel tank.
Figure 3-112. Gasoline Fuel Pressure and Temperature
Manifold Assembly
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SECTION 3 - CHASSIS & TURNTABLE

Fuel Filter

After the fuel is drawn into the fuel pump, the fuel flows
through the gasoline fuel filter. The fuel filter will trap small
particles as the fuel passes through the filter to remove debris
and prevents the fuel pressure and temperature manifold and
fuel injectors from becoming damaged. Maintenance of the
fuel filter is required as indicated in Section 1.

Fuel Injector Rail

Fuel flows from the fuel pressure and temperature manifold
assembly to the fuel rails where the fuel is delivered to the fuel
injectors. The fuel rail also contains a Schrader valve which is
utilized to test the regulated pressure of the fuel system.

Fuel Injector

The fuel supply is maintained on the top of the injector from
the injector rail. The injector is fed a "pulse" signal through the
wire harness which causes the injector to open. During regular
operating conditions the ECM controls the opening and dura-
tion of opening of the injector. During lower RPM operation
the injector signals or "pulses" are less frequent then when the
engine is operating at higher RPMs. The engine has been cali-
brated to deliver the precise amount of fuel for optimum per-
formance and emission control.
3-137