Fuel System Description
The fuel pump module, located in the fuel tank, supplies fuel
through the fuel feed pipe to the high pressure mechanical fuel
injection pump. The mechanical fuel injection pump is located on
the lower left side of the engine. Fuel is drawn through the fuel
filter/heater element housing, which combines a water separator, a
fuel heater element, and a filter element. The mechanical fuel
injection pump output is controlled by the engine control module
(ECM), and provides fuel at the pressure needed by the fuel
injectors. The fuel injectors supply fuel directly to the
combustion chambers of the engine. A separate pipe returns unused
fuel through to the fuel tank. The mechanical fuel injection pump,
fuel rail pressure, fuel injection timing, and injection duration
are controlled by the ECM.
Fuel Tank
The fuel tank stores the fuel supply. The fuel pump could be an
electric pump that is attached to the primary fuel tank module
assembly. The fuel pump supplies fuel to the high pressure
mechanical fuel injection pump. The fuel pump also supplies fuel to
the siphon jet pump. The siphon jet pump draws fuel from the
secondary side of the fuel tank to the primary side of the fuel
tank. In an other variant the fuel tank module assembly supplies
fuel to the low pressure side mechanical fuel injection pump.
The fuel tank is held in place by 2 metal straps that attach to
the frame. The fuel tank is molded from high density
polyethylene.
Fuel Filler Cap
The fuel filler cap has a torque-limiting device that prevents
the cap from being over tightened. To install , turn the cap
clockwise until you hear audible clicks. This indicates that the
cap is fully seated.
Fuel Sender Assembly
The fuel tank module is located inside of the fuel tank. The
fuel tank module consists of the following major components:
• |
The fuel pump and reservoir
assembly (if equipped) |
Fuel Level Sensor
The fuel level sensor consists of a float, a wire float arm, and
a ceramic resistor card. The position of the float arm indicates
the fuel level. The fuel level sensor contains a variable resistor
which changes resistance in correspondence with the amount of fuel
in the fuel tank. The engine control module (ECM) sends the fuel
level information to the instrument panel cluster. This information
is used for the instrument panel fuel gauge and the low fuel
warning indicator, if applicable. The ECM also monitors the fuel
level input for various diagnostics.
Fuel Strainer
The fuel strainer attaches to the lower end of the fuel sender.
The fuel strainer is made of woven plastic. The functions of the
fuel strainer are to filter contaminants and to wick fuel. The fuel
strainer is self-cleaning and normally requires no maintenance.
Fuel stoppage at this point indicates that the fuel tank contains
an abnormal amount of sediment.
Fuel Pump
The fuel pump is mounted in the primary fuel tank module
reservoir. he fuel pump could be an electric pump that is attached
to the primary fuel tank module assembly. The fuel pump supplies
fuel to the high pressure mechanical fuel injection pump. The fuel
pump also supplies fuel to the siphon jet pump. The siphon jet pump
draws fuel from the secondary side of the fuel tank to the primary
side of the fuel tank. In an other variant the fuel tank module
assembly supplies fuel to the low pressure side mechanical fuel
injection pump. The control module controls the electric fuel pump
operation through a fuel pump relay.
Fuel Injection Pump
The fuel injection pump is a mechanical high pressure pump. The
fuel injection pump is located on the lower left side of the
engine. Fuel is pumped to the fuel rails at a specified pressure.
Fuel pressure is regulated by the fuel pressure regulator which is
located on the inlet side of the fuel injection pump, controlled by
the engine control module (ECM). Excess fuel from the fuel
injection pump returns to the fuel tank through the fuel return
pipe.
Fuel Filter
The fuel filter assembly is located at the right rear of the
engine compartment. The paper filter element traps particles in the
fuel that may damage the fuel injection system.
Fuel Feed and Return Pipes
The fuel feed pipe carries fuel from the fuel tank to the fuel
filter/heater element housing. The fuel return pipe carries fuel
from the fuel rail assemblies back to the fuel tank. The fuel pipes
consist of 2 sections:
• |
The rear fuel pipe assemblies
are located from the top of the fuel tank to the chassis fuel
pipes. The rear fuel pipes are constructed of steel with sections
of rubber hose covered with braiding. |
• |
The chassis fuel pipes are
located under the vehicle and connect the rear fuel pipes to the
fuel rail pipes. These pipes are constructed of steel with sections
of rubber hose covered with braiding. |
Quick-Connect Fittings
Quick-connect fittings provide a simplified means of installing
and connecting fuel system components. The fittings consist of a
unique female connector and a compatible male pipe end. O-rings,
located inside the female connector, provide the fuel seal.
Integral locking tabs inside the female connector hold the fittings
together.
Fuel Pipe O-Rings
O-rings seal the connections in the fuel system. Fuel system
O-ring seals are made of special material. Service the O-ring seals
with the correct service part.
Fuel Rail Assembly
The fuel rail assembly attaches to the cylinder head. The fuel
rail assembly distributes pressurized fuel to the fuel injectors
through the fuel lines.
The fuel rail pressure sensor gives the engine control module
(ECM) an indication of fuel pressure. The ECM uses this information
to regulate fuel pressure, by commanding the fuel pressure
regulator open or closed on the inlet of the fuel injection
pump.
Fuel Injectors and Return Lines
A fuel injector is a solenoid device, controlled by the ECM,
that meters pressurized fuel to a single engine cylinder. Fuel
pressure is released from above the fuel injector pintle, and is
returned to the fuel tank through the fuel return lines. The
difference in fuel pressure above and below the pintle causes the
pintle to open. Fuel from the fuel injector tip is sprayed directly
into the combustion chamber on the compression stroke of the
engine.
The control functions for the fuel injection system are
integrated in the engine control module (ECM).
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