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FUEL SYSTEM—2.5L DIESEL ENGINE
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FUEL SYSTEM—2.5L DIESEL ENGINE
TABLE OF CONTENTS
page
page
FUEL DELIVERY SYSTEM—2.5L DIESEL
FUEL INJECTION SYSTEM—2.5L DIESEL
FUEL DELIVERY SYSTEM—2.5L DIESEL ENGINE
TABLE OF CONTENTS
page
page
DESCRIPTION AND OPERATION
FUEL TUBES/LINES/HOSES AND CLAMPS—
QUICK-CONNECT FITTINGS—LOW
DIAGNOSIS AND TESTING
FUEL INJECTOR / NEEDLE MOVEMENT
SERVICE PROCEDURES
REMOVAL AND INSTALLATION
SPECIFICATIONS
DESCRIPTION AND OPERATION
trolled by the PCM, refer to the Fuel Injection Sys-
tem—2.5L Diesel Engine section of this group.
The fuel heater relay, fuel heater and fuel gauge
are not operated by the PCM. These components are
controlled by the ignition (key) switch. All other fuel
system electrical components necessary to operate
the engine are controlled or regulated by the PCM.
INTRODUCTION
DESCRIPTION
This Fuel Delivery section will cover components
not
controlled
by
the
PCM.
For
components
con-
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FUEL SYSTEM—2.5L DIESEL ENGINE
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DESCRIPTION AND OPERATION (Continued)
FUEL SYSTEM PRESSURE WARNING
FUEL TANK MODULE
DESCRIPTION
DESCRIPTION
An electric fuel pump is not attached to the fuel
tank
WARNING: HIGH–PRESSURE FUEL LINES DELIVER
DIESEL FUEL UNDER EXTREME PRESSURE FROM
THE INJECTION PUMP TO THE FUEL INJECTORS.
THIS MAY BE AS HIGH AS 45,000 KPA (6526 PSI).
USE EXTREME CAUTION WHEN INSPECTING FOR
HIGH–PRESSURE FUEL LEAKS. INSPECT FOR
HIGH–PRESSURE FUEL LEAKS WITH A SHEET OF
CARDBOARD
module
for
diesel
powered
engines.
Fuel
is
drawn by the fuel injection pump.
The fuel tank module is installed in the top of the
fuel tank. The fuel tank module contains the follow-
ing components:
²
Fuel reservoir
²
Electric fuel gauge sending unit
(Fig.
1).
HIGH
FUEL
INJECTION
²
Fuel supply line connection
PRESSURE
CAN
CAUSE
PERSONAL
INJURY
IF
²
Fuel return line connection
CONTACT IS MADE WITH THE SKIN.
²
Wire harness
²
Fuel inlet filter (Strainer)
FUEL GAUGE SENDING UNIT
DESCRIPTION
The fuel gauge sending unit is attached to the side
of the fuel pump module. The sending unit consists of
a float, an arm, and a variable resistor (track). The
track is used to send an electrical signal used for fuel
gauge operation.
As the fuel level increases, the float and arm move
up. This decreases the sending unit resistance, caus-
ing the PCM to send a signal to the fuel gauge on the
instrument panel to read full. As the fuel level
decreases, the float and arm move down. This
increases the sending unit resistance, causing the
PCM to send a signal to the fuel gauge on the instru-
ment panel to move toward empty.
FUEL FILTER/WATER SEPARATOR
DESCRIPTION
The fuel filter/water separator assembly is located
in the engine compartment near the strut tower (Fig.
2).
The combination fuel filter/water separator pro-
tects the fuel injection pump by helping to remove
water and contaminants from the fuel. Moisture col-
lects at the bottom of the filter/separator in a plastic
bowl.
The fuel filter/water separator assembly contains
the fuel filter, fuel heater element, and water drain
valve.
For information on the fuel heater, refer to Fuel
Heater in this group.
Refer to the maintenance schedules in Group 0 in
this manual for the recommended fuel filter replace-
ment intervals.
For periodic draining of water from the bowl, refer
to Fuel Filter/Water Separator Removal/Installation
in this group.
Fig. 1 Typical Fuel Pressure Test at Injection Pump
1 – FITTING
2 – HIGH PRESSURE LINE
3 – CARDBOARD
FUEL TANK
DESCRIPTION
The fuel tank and tank mounting used with the
diesel powered engine is the same as used with gas-
oline powered models, although the fuel tank module
is different.
The fuel tank contains the fuel tank module and
one rollover valve. Two fuel lines are routed to the
fuel tank module. One line is used for fuel supply to
the fuel filter/water separator. The other is used to
return excess fuel back to the fuel tank.
The fuel tank module contains the fuel gauge elec-
trical sending unit. An electric fuel pump is not
used with the diesel engine.
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FUEL SYSTEM—2.5L DIESEL ENGINE
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DESCRIPTION AND OPERATION (Continued)
Fig. 3 Fuel Injection Pump
1 – FUEL INJECTION PUMP ASSEMBLY
2 – FUEL RETURN LINE
3 – FUEL SUPPLY LINE
4 – FUEL INJECTION PUMP 10–WAY CONNECTOR
5 – TIMING SOLENOID
6 – OVERFLOW VALVE
Fig. 2 Fuel Filter/Water Separator Location
FUEL SHUTDOWN SOLENOID
DESCRIPTION
The fuel shutdown solenoid is controlled and
operated by the ECM.
The fuel shutdown (shut-off) solenoid is used to
electrically shut off the diesel fuel supply to the high-
pressure
amount of fuel and the time the fuel is injected is
controlled by the vehicle’s ECM, instead of by a
mechanical governor assembly. A solenoid controlled
by the ECM is used in place of the mechanical gov-
ernor assembly, and it moves a control sleeve inside
the pump that regulates the amount of fuel being
injected. There is no mechanical connection between
the accelerator pedal and the electronically controlled
injection pump. Instead, a sensor connected to the
accelerator pedal sends a signal to the ECM that rep-
resents the actual position of the accelerator pedal.
The ECM uses this input, along with input from
other sensors to move the control sleeve to deliver
the appropriate amount of fuel. This system is known
as “Drive-By-Wire”
The actual time that the fuel is delivered is very
important to the diesel combustion process. The ECM
monitors outputs from the engine speed sensor (fly-
wheel position in degrees), and the fuel injector sen-
sor (mechanical movement within the #1 cylinder
fuel injector). Outputs from the Accelerator Pedal
Position sensor, engine speed sensor (engine rpm)
and engine coolant temperature sensor are also used.
The ECM will then compare its set values to these
outputs to electrically adjust the fuel timing (amount
of advance) within the injection pump. This is
referred to as “Closed Loop” operation. The ECM
monitors fuel timing by comparing its set value to
when the injector #1 opens. If the value is greater
than a preset value a fault will be set.
fuel
injection
pump.
The
solenoid
is
mounted to the rear of the injection pump.
The solenoid controls starting and stopping of the
engine regardless of the position of the accelerator
pedal. When the ignition (key) switch is OFF, the
solenoid is shut off and fuel flow is not allowed to the
fuel injection pump. When the key is placed in the
ON or START positions, fuel supply is allowed at the
injection pump.
FUEL INJECTION PUMP
DESCRIPTION
The fuel injection pump is a mechanical distribu-
tor–type, Bosch VP36 series (Fig. 3). A gear on the
end of the injection pump shaft meshes with the
drive gear at the front of engine. The pump is
mechanically timed to the engine. The ECM regu-
lates the timing of the injection pump.
The injection pump contains the fuel shutdown
solenoid, fuel temperature sensor, control sleeve sen-
sor, fuel quantity actuator and the fuel timing sole-
noid (Fig. 3).
In the electronically controlled injection pump, the
pump plunger works the same as the pump plunger
in a mechanically controlled injection pump, but the
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FUEL SYSTEM—2.5L DIESEL ENGINE
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DESCRIPTION AND OPERATION (Continued)
Actual electric fuel timing (amount of advance) is
accomplished by the fuel timing solenoid mounted to
the bottom of the injection pump (Fig. 3). Fuel timing
will be adjusted by the ECM, which controls the fuel
timing solenoid.
An overflow valve is attached into the fuel return
line at the rear of the fuel injection pump (Fig. 3).
This valve serves two purposes. One is to ensure that
a certain amount of residual pressure is maintained
within the pump when the engine is switched off.
This will prevent the fuel timing mechanism within
the injection pump from returning to its zero posi-
tion. The other purpose is to allow excess fuel to be
returned to the fuel tank through the fuel return
line. The pressure values within this valve are preset
and can not be adjusted.
The fuel injection pump supplies high–pressure
fuel of approximately 45,000 kPa (6526 psi) to each
injector in precise metered amounts at the correct
time.
For mechanical injection pump timing, refer to
Fuel Injection Pump Timing in the Service Proce-
dures section of this group.
open, it sends a small voltage spike pulse to the
ECM. This tells the ECM that the #1 cylinder injec-
tor is firing. It is not used with the other three injec-
tors.
Fig. 5 Fuel Injector Sensor
1 – NEEDLE MOVEMENT SENSOR
2 – FUEL INJECTOR (NUMBER 1 CYLINDER ONLY)
3 – COPPER WASHER
4 – SENSOR CONNECTOR
FUEL INJECTORS
DESCRIPTION
The fuel injectors have controlled internal leakage
which colls the injectors. Fuel drain tubes (Fig. 4) are
used to route this fuel back to the overflow valve at
the rear of the injection pump. This excess fuel is
then
Fuel enters the injector at the fuel inlet (top of
injector) and is routed to the needle valve bore. When
fuel pressure rises to approximately 15,000–15,800
kPa (2175–2291 psi), the needle valve spring tension
is overcome. The needle valve rises and fuel flows
through the spray holes in the nozzle tip into the
combustion chamber. The pressure required to lift
the needle valve is the injector opening pressure set-
ting. This is referred to as the “pop-off” pressure set-
ting.
Fuel pressure in the injector circuit decreases after
injection. The injector needle valve is immediately
closed by the needle valve spring and fuel flow into
the combustion chamber is stopped. Exhaust gases
are prevented from entering the injector nozzle by
the needle valve.
A copper washer (gasket) is used at the base of
each injector (Fig. 5) to prevent combustion gases
from escaping.
Fuel injector firing sequence is 1–3–4–2.
returned
to
the
fuel
tank
through
the
fuel
return line.
Fig. 4 Fuel Injectors and Drain Tubes
The injectors are connected to the fuel injection
pump by the high– pressure fuel lines. A separate
injector is used for each of the four cylinders. An
injector containing a sensor (Fig. 5) is used on the
number one cylinder injector. This injector is called
instrumented injector #1 or needle movement sensor.
It is used to tell the ECM when the #1 injector’s
internal spring-loaded valve seat has been forced
open by pressurized fuel being delivered to the cylin-
der, which is at the end of its compression stroke.
When the instrumented injector’s valve seat is force
FUEL TUBES/LINES/HOSES AND CLAMPS—
LOW-PRESSURE TYPE
DESCRIPTION
Also refer to the proceeding section on Quick–Con-
nect Fittings.
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FUEL SYSTEM—2.5L DIESEL ENGINE
14 - 5
DESCRIPTION AND OPERATION (Continued)
Inspect all hose connections such as clamps, cou-
plings and fittings to make sure they are secure and
leaks are not present. The component should be
replaced immediately if there is any evidence of deg-
radation that could result in failure.
Never attempt to repair a plastic fuel line/tube or a
quick–connect fitting. Replace complete line/tube as
necessary.
Avoid contact of any fuel tubes/hoses with other
vehicle components that could cause abrasions or
scuffing. Be sure that the fuel lines/tubes are prop-
erly routed to prevent pinching and to avoid heat
sources.
The lines/tubes/hoses are of a special construction.
If it is necessary to replace these lines/tubes/hoses,
use only original equipment type.
The hose clamps used to secure the rubber hoses
are of a special rolled edge construction. This con-
struction is used to prevent the edge of the clamp
from cutting into the hose. Only these rolled edge
type clamps may be used in this system. All other
types of clamps may cut into the hoses and cause
fuel leaks.
Where a rubber hose is joined to a metal tube
(staked), do not attempt to repair. Replace entire
line/tube assembly.
Use new original equipment type hose clamps.
Tighten hose clamps to 2 N·m (20 in. lbs.) torque.
Fig. 6 Plastic Retainer Ring-Type Fitting
1 – FUEL TUBE
2 – QUICK CONNECT FITTING
3 – PUSH
4 – PLASTIC RETAINER
5 – PUSH
6 – PUSH
7 – PUSH
8 – PUSH
QUICK-CONNECT FITTINGS—LOW PRESSURE
TYPE
repair lines that are damaged. Only use the recom-
mended lines when replacement of high–pressure
fuel line is necessary.
DESCRIPTION
Different types of quick-connect fittings are used to
attach various fuel system components. These are: a
single-tab type, a two-tab type or a plastic retainer
ring type (Fig. 6). Refer to Quick-Connect Fittings in
the Removal/Installation section for more informa-
tion.
High–pressure fuel lines deliver fuel under pres-
sure of up to approximately 45,000 kPa (6526 PSI)
from the injection pump to the fuel injectors. The
lines expand and contract from the high–pressure
fuel pulses generated during the injection process. All
high–pressure fuel lines are of the same length and
inside diameter. Correct high–pressure fuel line
usage and installation is critical to smooth engine
operation.
CAUTION: The interior components (o-rings, spac-
ers) of quick-connect fitting are not serviced sepa-
rately, but new pull tabs are available for some
types. Do not attempt to repair damaged fittings or
fuel lines/tubes. If repair is necessary, replace the
complete fuel tube assembly.
WARNING: USE EXTREME CAUTION WHEN
INSPECTING FOR HIGH–PRESSURE FUEL LEAKS.
INSPECT FOR HIGH–PRESSURE FUEL LEAKS WITH
A SHEET OF CARDBOARD. HIGH FUEL INJECTION
PRESSURE
HIGH-PRESSURE FUEL LINES
CAN
CAUSE
PERSONAL
INJURY
IF
DESCRIPTION
CONTACT IS MADE WITH THE SKIN.
CAUTION: The high–pressure fuel lines must be
held securely in place in their holders. The lines
cannot contact each other or other components. Do
not attempt to weld high–pressure fuel lines or to
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