Dodge Durango (DN). Manual — part 9

Fuel is supplied to the filter/regulator by the elec-

tric fuel pump through an opening tube at the bot-
tom of filter/regulator (Fig. 3).

The regulator acts as a check valve to maintain

some fuel pressure when the engine is not operating.
This will help to start the engine. A second check
valve is located at the outlet end of the electric fuel
pump. Refer to Fuel Pump—Description and
Operation for more information. Also refer to
the Fuel Pressure Leak Down Test and the Fuel
Pump Pressure Tests.

If fuel pressure at the pressure regulator exceeds

approximately 49.2 psi, an internal diaphragm opens
and excess fuel pressure is routed back into the tank
through the bottom of pressure regulator.

Both fuel filters (at bottom of fuel pump module

and within fuel pressure regulator) are designed for
extended service. They do not require normal sched-
uled maintenance. Filters should only be replaced if
a diagnostic procedure indicates to do so.

FUEL TANK

DESCRIPTION

The fuel tank is constructed of a plastic material.

Its main functions are for fuel storage and for place-
ment of the fuel pump module.

OPERATION

All models pass a full 360 degree rollover test

without fuel leakage. To accomplish this, fuel and

vapor flow controls are required for all fuel tank con-
nections.

A rollover valve(s) is mounted into the top of the

fuel tank (or pump module). Refer to Emission Con-
trol System for rollover valve information.

An evaporation control system is connected to the

rollover valve(s) to reduce emissions of fuel vapors
into the atmosphere. When fuel evaporates from the
fuel tank, vapors pass through vent hoses or tubes to
a charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP). Refer to Emission Control
System for additional information.

FUEL INJECTORS

DESCRIPTION

An individual fuel injector (Fig. 4) is used for each

individual cylinder.

OPERATION

The top (fuel entry) end of the injector (Fig. 4) is

attached into an opening on the fuel rail.

The fuel injectors are electrical solenoids. The

injector contains a pintle that closes off an orifice at
the nozzle end. When electric current is supplied to
the injector, the armature and needle move a short
distance against a spring, allowing fuel to flow out
the orifice. Because the fuel is under high pressure, a
fine spray is developed in the shape of a pencil
stream. The spraying action atomizes the fuel, add-
ing it to the air entering the combustion chamber.

The nozzle (outlet) ends of the injectors are posi-

tioned into openings in the intake manifold just
above the intake valve ports of the cylinder head.

Fig. 3 Side View—Filter/Regulator

1 – INTERNAL FUEL FILTER
2 – FUEL FLOW TO FUEL INJECTORS
3 – FUEL FILTER/FUEL PRESSURE REGULATOR
4 – EXCESS FUEL BACK TO TANK
5 – FUEL INLET
6 – RUBBER GROMMET
7 – TOP OF PUMP MODULE

Fig. 4 Fuel Injector—Typical

1 – FUEL INJECTOR
2 – NOZZLE
3 – TOP (FUEL ENTRY)

14 - 4

FUEL SYSTEM

DN

DESCRIPTION AND OPERATION (Continued)

The engine wiring harness connector for each fuel
injector is equipped with an attached numerical tag
(INJ 1, INJ 2 etc.). This is used to identify each fuel
injector.

The injectors are energized individually in a

sequential order by the powertrain control module
(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust
injector pulse width based on various inputs it
receives.

Battery voltage is supplied to the injectors through

the ASD relay.

The PCM determines injector pulse width based on

various inputs.

FUEL RAIL—3.9/5.2/5.9L ENGINES

DESCRIPTION

The fuel injector rail is used to attach the fuel

injectors to the engine. It is mounted to the engine
(Fig. 5).

OPERATION

High pressure from the fuel pump is routed to the

fuel rail. The fuel rail then supplies the necessary
fuel to each individual fuel injector.

A fuel pressure test port is located on the fuel rail.

A quick-connect fitting with a safety latch clip is
used to attach the fuel line to the fuel rail.

The fuel rail is not repairable.

CAUTION: The left and right sections of the fuel rail
are connected with a flexible connecting hose. Do
not attempt to separate the rail halves at this con-
necting hose. Due to the design of this connecting
hose, it does not use any clamps. Never attempt to
install a clamping device of any kind to the hose.
When removing the fuel rail assembly for any rea-
son, be careful not to bend or kink the connecting
hose.

FUEL INJECTOR RAIL—4.7L ENGINE

DESCRIPTION

The fuel injector rail is used to mount the fuel

injectors to the engine. It is mounted to the intake
manifold (Fig. 6).

OPERATION

High pressure fuel from the fuel pump is routed to

the fuel rail. The fuel rail then supplies the neces-
sary fuel to each individual fuel injector.

A fuel pressure test port is located on the fuel rail

(Fig. 6). A quick-connect fitting with a safety latch is
used to attach the fuel line to the fuel rail.

The fuel rail is not repairable.

CAUTION: 4.7L Engine Only: The left and right sec-
tions of the fuel rail are joined with a connector
tube (Fig. 6). Do not attempt to separate the rail
halves at this tube. Due to the design of this con-
necting tube, it does not use any clamps. Never
attempt to install a clamping device of any kind to
the tube. When removing the fuel rail assembly for
any reason, be careful not to bend or kink the con-
nector tube.

FUEL TANK FILLER TUBE CAP

DESCRIPTION

The plastic fuel tank filler tube cap is threaded

onto the end of the fuel fill tube. Certain models are
equipped with a 1/4 turn cap.

OPERATION

The loss of any fuel or vapor out of fuel filler tube

is prevented by the use of a pressure-vacuum fuel fill
cap. Relief valves inside the cap will release fuel tank
pressure at predetermined pressures. Fuel tank vac-
uum will also be released at predetermined values.
This cap must be replaced by a similar unit if
replacement is necessary. This is in order for the sys-
tem to remain effective.

Fig. 5 Fuel Rail—3.9/5.2/5.9L Engine—Typical

1 – FUEL RAIL CONNECTING HOSE
2 – FUEL RAIL
3 – MOUNTING BOLTS (4)

DN

FUEL SYSTEM

14 - 5

DESCRIPTION AND OPERATION (Continued)

CAUTION: Remove fill cap before servicing any fuel
system component to relieve tank pressure. If
equipped with a California emissions package and a
Leak Detection Pump (LDP), the cap must be tight-
ened securely. If cap is left loose, a Diagnostic
Trouble Code (DTC) may be set.

FUEL TUBES/LINES/HOSES AND CLAMPS

DESCRIPTION

Also refer to Quick-Connect Fittings.

WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).

BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
SYSTEM PRESSURE RELEASE PROCEDURE IN
THIS GROUP.

The lines/tubes/hoses used on fuel injected vehicles

are of a special construction. This is due to the
higher fuel pressures and the possibility of contami-
nated fuel in this system. If it is necessary to replace
these lines/tubes/hoses, only those marked EFM/EFI
may be used.

If equipped: The hose clamps used to secure rub-

ber hoses on fuel injected vehicles are of a special
rolled edge construction. This construction 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 high-pressure fuel leaks.

Use new original equipment type hose clamps.

QUICK-CONNECT FITTINGS

DESCRIPTION

Different types of quick-connect fittings are used to

attach various fuel system components, lines and
tubes. These are: a single-tab type, a two-tab type or
a plastic retainer ring type. Some are equipped with
safety latch clips. Some may require the use of a spe-
cial tool for disconnection and removal. Refer to
Quick-Connect Fittings Removal/Installation for more
information.

CAUTION: The interior components (o-rings, clips)
of quick-connect fittings are not serviced sepa-
rately, but new plastic spacers are available for
some types. If service parts are not available, do
not attempt to repair the damaged fitting or fuel line
(tube). If repair is necessary, replace the complete
fuel line (tube) assembly.

DIAGNOSIS AND TESTING

FUEL PUMP PRESSURE TEST

Use this test in conjunction with the Fuel Pump

Capacity Test, Fuel Pressure Leak Down Test and
Fuel Pump Amperage Test found elsewhere in this
group.

Check Valve Operation: The electric fuel pump

outlet contains a one-way check valve to prevent fuel
flow back into the tank and to maintain fuel supply
line pressure (engine warm) when pump is not oper-
ational. It is also used to keep the fuel supply line
full of gasoline when pump is not operational. After
the vehicle has cooled down, fuel pressure may drop

Fig. 6 Fuel Injector Rail—4.7L V-8 Engine

1 – MOUNTING BOLTS (4)
2 – INJ.#7
3 – INJ.#5
4 – QUICK-CONNECT FITTING
5 – INJ.#3
6 – FUEL INJECTOR RAIL
7 – INJ.#1
8 – CONNECTOR TUBE
9 – INJ.#2
10 – INJ.#4
11 – INJ.#6
12 – INJ.#8
13 – PRESSURE TEST PORT CAP

14 - 6

FUEL SYSTEM

DN

DESCRIPTION AND OPERATION (Continued)

to 0 psi (cold fluid contracts), but liquid gasoline will
remain in fuel supply line between the check valve
and

fuel

injectors.

Fuel

pressure

that

has

dropped to 0 psi on a cooled down vehicle
(engine off) is a normal condition. When the elec-
tric fuel pump is activated, fuel pressure should
immediately (1–2 seconds) rise to specification.

All fuel systems are equipped with a fuel tank

module mounted, combination fuel filter/fuel pressure
regulator. The fuel pressure regulator is not con-
trolled by engine vacuum.

WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT FUEL PRESSURE EVEN WITH THE ENGINE
OFF. BEFORE DISCONNECTING FUEL LINE AT
FUEL RAIL, THIS PRESSURE MUST BE RELEASED.
REFER

TO

THE

FUEL

SYSTEM

PRESSURE

RELEASE PROCEDURE.

(1) Remove protective cap at fuel rail test port.

Connect the 0–414 kPa (0-60 psi) fuel pressure gauge
(from gauge set 5069) to test port pressure fitting on
fuel rail (Fig. 7). The DRB III Scan Tool along
with the PEP module, the 500 psi pressure
transducer,

and

the

transducer-to-test

port

adapter may also be used in place of the fuel
pressure gauge.

(2) Start and warm engine and note pressure

gauge reading. Fuel pressure should be 339 kPa

6 34

kPa (49.2 psi

6 5 psi) at idle.

(3) If engine runs, but pressure is below 44.2 psi,

check for a kinked fuel supply line somewhere
between fuel rail and fuel pump module. If line is not
kinked, but specifications for either the Fuel Pump

Capacity, Fuel Pump Amperage or Fuel Pressure
Leak Down Tests were not met, replace fuel pump
module

assembly.

Refer

to

Fuel

Pump

Module

Removal/Installation.

(4) If operating pressure is above 54.2 psi, electric

fuel pump is OK, but fuel pressure regulator is defec-
tive. Replace fuel filter/fuel pressure regulator. Refer
to Fuel Filter/Fuel Pressure Regulator Removal/In-
stallation for more information.

(5) Install protective cap to fuel rail test port.

FUEL PUMP CAPACITY TEST

Before performing this test, verify fuel pump

pressure. Refer to Fuel Pump Pressure Test.
Use this test in conjunction with the Fuel Pres-
sure Leak Down Test.

(1) Release fuel system pressure. Refer to Fuel

Pressure Release Procedure.

(2) Disconnect fuel supply line at fuel rail. Refer to

Quick-Connect Fittings. Some engines may require
air cleaner housing removal before line disconnection.

(3) Obtain correct Fuel Line Pressure Test Adapter

Tool Hose. Tool number 6539 is used for 5/16” fuel
lines and tool number 6631 is used for 3/8” fuel lines.

(4) Connect

correct

Fuel

Line

Pressure

Test

Adapter Tool Hose into disconnected fuel supply line.
Insert other end of Adaptor Tool Hose into a gradu-
ated container.

(5) Remove fuel fill cap.
(6) To activate fuel pump and pressurize system,

obtain DRB scan tool and actuate ASD Fuel System
Test.

(7) A good fuel pump will deliver at least 1/4 liter

of fuel in 7 seconds. Do not operate fuel pump for
longer than 7 seconds with fuel line disconnected as
fuel pump module reservoir may run empty.

(a) If capacity is lower than specification, but

fuel pump can be heard operating through fuel fill
cap opening, check for a kinked/damaged fuel sup-
ply line somewhere between fuel rail and fuel
pump module.

(b) If line is not kinked/damaged, and fuel pres-

sure is OK, but capacity is low, replace fuel filter/
fuel pressure regulator. The filter/regulator may be
serviced separately on certain applications. Refer
to Fuel Filter/Fuel Pressure Regulator Removal/In-
stallation for additional information.

(c) If both fuel pressure and capacity are low,

replace fuel pump module assembly. Refer to Fuel
Pump Module Removal/Installation.

FUEL PRESSURE LEAK DOWN TEST

Use this test in conjunction with the Fuel Pump

Pressure Test and Fuel Pump Capacity Test.

Check Valve Operation: The electric fuel pump

outlet contains a one-way check valve to prevent fuel

Fig. 7 Fuel Pressure Test Gauge (Typical Gauge

Installation at Test Port)

1 – SERVICE (TEST) PORT
2 – FUEL PRESSURE TEST GAUGE
3 – FUEL RAIL

DN

FUEL SYSTEM

14 - 7

DIAGNOSIS AND TESTING (Continued)