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FUEL SYSTEM 14 - 1
FUEL SYSTEM
CONTENTS
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page
ACCELERATOR PEDAL AND THROTTLE
CABLE ..............................
FUEL DELIVERY SYSTEM ..................
FUEL TANKS ...........................
GENERAL INFORMATION ..................
MPI SYSTEM—4.0L ENGINE—COMPONENT
DESCRIPTION/SYSTEM OPERATION .......
MPI SYSTEM—4.0L ENGINE—COMPONENT
REMOVAL/INSTALLATION ...............
MPI SYSTEM—4.0L ENGINE—GENERAL
DIAGNOSIS ..........................
MPI SYSTEM—5.2L ENGINE—COMPONENT
DESCRIPTION/SYSTEM OPERATION .......
MPI SYSTEM—5.2L ENGINE—COMPONENT
REMOVAL/INSTALLATION ...............
MPI SYSTEM—5.2L ENGINE—GENERAL
DIAGNOSIS ..........................
SPECIFICATIONS .......................
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation or
by the particular vehicle nameplate. A chart showing
a breakdown of the alphabetical designations is in-
cluded in the Introduction section at the beginning of
this manual.
The
Fuel System
consists of: the fuel tank, an
electric (fuel tank mounted) fuel pump and fuel filter.
It also consists of fuel tubes/lines/hoses, vacuum
hoses, throttle body and fuel injectors.
The
Fuel Delivery System
consists of: the electric
fuel pump, fuel filter, fuel tubes/lines/hoses, fuel rail,
fuel injectors and fuel pressure regulator.
A
Fuel Return System
is used on all vehicles. The
system consists of: the fuel tubes/lines/hoses that
route fuel back to the fuel tank.
The
Fuel Tank Assembly
consists of: the fuel
tank, filler tube, fuel gauge sending unit/electric fuel
pump module, a pressure relief/rollover valve and a
pressure-vacuum filler cap.
Also to be considered part of the fuel system is the
Evaporation Control System.
This is designed to
reduce the emission of fuel vapors into the atmo-
sphere. The description and function of the Evapora-
tive Control System is found in Group 25, Emission
Control Systems.
can cause damage and should be reported to
your dealer immediately.
Engine damage as a re-
sult of heavy knock operation may not be covered by
the new vehicle warranty.
In addition to using unleaded gasoline with the
proper octane rating,
those that contain deter-
gents, corrosion and stability additives are rec-
ommended.
Using gasolines that have these addi-
tives will help improve fuel economy, reduce
emissions and maintain vehicle performance. Gener-
ally, premium unleaded gasolines contain more addi-
tive than regular unleaded gasolines.
Poor quality gasoline
can cause problems such as
hard starting, stalling and stumble. If you experience
these problems, use another brand of gasoline before
considering service for the vehicle.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with
materials that contain oxygen such as alcohol, MTBE
and ETBE. The type and amount of oxygenate used in
the blend is important. The following are generally
used in gasoline blends:
ETHANOL
Ethanol (Ethyl or Grain Alcohol) properly blended,
is used as a mixture of 10 percent ethanol and 90
percent gasoline.
Gasoline with ethanol may be
used in your vehicle.
FUEL USAGE STATEMENT
Your vehicle was designed to meet all emission
regulations and provide excellent fuel economy using
high quality unleaded gasoline. Only use unleaded
gasolines having a minimum posted octane of 87.
If your vehicle develops occasional light spark
knock (ping) at low engine speeds, this is not harmful.
However,
continued heavy knock at high speeds
 14 - 2 FUEL SYSTEM
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METHANOL
15 percent MTBE. Gasoline and ETBE (Ethyl Ter-
tiary Butyl Ether) are blends of gasoline and up to 17
percent ETBE. Gasoline blended with MTBE or
ETBE may be used in your vehicle.
CAUTION: DO NOT USE GASOLINES CONTAINING
METHANOL.
Use of methanol/gasoline blends may re-
sult in starting and driveability problems. In addition,
damage may be done to critical fuel system compo-
nents.
CLEAN AIR GASOLINE
Many gasolines are now being blended that contrib-
ute to cleaner air, especially in those areas of the
country where air pollution levels are high. These
new blends provide a cleaner burning fuel and some
are referred to as
Reformulated Gasoline
.
In areas of the country where carbon monoxide
levels are high, gasolines are being treated with oxy-
genated materials such as MTBE, ETBE and ethanol.
Chrysler Corporation supports these efforts toward
cleaner air and recommends that you use these gaso-
lines as they become available.
Methanol (Methyl or Wood Alcohol) is used in a
variety of concentrations blended with unleaded gaso-
line. You may encounter fuels containing 3 percent or
more methanol along with other alcohols called cosol-
vents.
Problems that are the result of using
methanol/gasoline blends are not the responsibility of
Chrysler Corporation. They may not be covered by
the vehicle warranty.
MTBE/ETBE
Gasoline and MTBE (Methyl Tertiary Butyl Ether)
blends are a mixture of unleaded gasoline and up to
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FUEL SYSTEM 14 - 3
FUEL DELIVERY SYSTEM
INDEX
page
page
Fuel Filter ..............................
Fuel Pressure Leak Down Test ...............
Fuel Pressure Release Procedure .............
Fuel Pump Capacity Test ...................
Fuel Pump Control ........................
Fuel Pump Module ........................
Fuel System Pressure Test ...................
Fuel Tubes/Lines/Hoses and Clamps ...........
Quick-Connect Fittings .....................
FUEL PUMP MODULE
The fuel pump module (Fig. 1) is installed in the top
of the fuel tank. The fuel pump module contains the
following components:
²
line. When the fuel pump is not operating, system fuel
pressure of 131-269 kPa (19-39 psi) is maintained. This
is done by the fuel pump outlet check valve and the
vacuum assisted fuel pressure regulator.
Electric fuel pump
²
Fuel pump reservoir
REMOVAL
²
In-tank fuel filter
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING THE FUEL PUMP MODULE,
THE FUEL SYSTEM PRESSURE MUST BE RE-
LEASED. REFER TO THE FUEL PRESSURE RE-
LEASE PROCEDURE IN THIS GROUP.
²
Fuel gauge sending unit
²
Fuel supply and return tube connections
(1) Drain and remove the fuel tank. Refer to Fuel
Tank removal and installation in the Fuel Tank sec-
tion of this group.
(2) The fuel pump module locknut is threaded onto
the fuel tank. Remove the fuel pump module locknut
(Fig. 2). The fuel pump module will spring up from
the fuel tank after the locknut has been removed.
Fig. 1 Fuel Pump Module
The fuel pump used on all vehicles is a gear/rotor
type pump. It is driven by a permanent magnet 12
volt electric motor that is immersed in the fuel tank.
The electrical pump is integral with the fuel sender
unit. The pump/sender assembly is installed inside
the fuel tank.
The fuel pump has a check valve at the outlet end that
consists of a ball held against a seat by force applied
from a spring. When the pump is operating, fuel pres-
sure overcomes spring pressure and forces the ball off its
seat, allowing fuel to flow. When the pump is not operat-
ing, spring pressure forces the ball back against the seat
preventing fuel backflow through the pump.
Fuel system pressure is maintained at approximately
214 kPa (31 psi). This is when the pump is operating
and vacuum is supplied to the fuel pressure regulator. If
vacuum is not supplied to the pressure regulator, fuel
pressure will be approximately 55-69 kPa (8-10 psi)
higher. This may be due to a broken or clogged vacuum
Fig. 2 Top View of Fuel Pump Module
(3) Remove module from fuel tank.
INSTALLATION
CAUTION: Whenever the fuel pump module is ser-
viced, the rubber gasket must be replaced.
(1) Clean the fuel tank at the module opening.
 14 - 4 FUEL SYSTEM
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(2) Using a new gasket on the fuel tank (Fig. 3),
position fuel pump module into opening in fuel tank.
Fig. 3 Rubber Gasket
CAUTION: The arrow on the top of the fuel pump
module must be facing in the direction shown in
Figure 2.
Fig. 4 Power Distribution Center
(3) Tighten locknut.
(4) Install fuel tank. Refer to Fuel Tank Installa-
tion in this group.
(1) Disconnect negative battery cable.
(2) Remove fuel tank filler neck cap to release fuel
tank pressure.
FUEL PUMP REPLACEMENT
The electric fuel pump is not serviceable. If the fuel
pump needs replacement, the complete fuel pump mod-
ule must be replaced. Refer to the previous procedure.
WARNING: DO NOT ALLOW FUEL TO SPILL ONTO
THE ENGINE INTAKE OR EXHAUST MANIFOLDS.
PLACE SHOP TOWELS UNDER AND AROUND THE
PRESSURE PORT TO ABSORB FUEL WHEN THE
PRESSURE IS RELEASED FROM THE FUEL RAIL.
FUEL GAUGE SENDING UNIT REPLACEMENT
The fuel gauge sending unit is not serviceable. If
the unit needs replacement, the complete fuel pump
module must be replaced.
WARNING: WEAR PROPER EYE PROTECTION
WHEN RELEASING FUEL SYSTEM PRESSURE.
FUEL PUMP CONTROL
The Powertrain Control Module (PCM) computer ener-
gizes the fuel pump through the Fuel Pump Relay. Bat-
tery voltage is applied to the relay from the ignition
switch. The coil in the relay is energized when a ground
is provided by the PCM. The relay is located in the
Power Distribution Center (PDC) next to the battery
(Fig. 4). For location of relay within the PDC, refer to
label under PDC cover. The ballast resistor and ballast
resistor bypass relay (as used with 4.0L engines of previ-
ous years), is no longer used to control fuel pump opera-
tion.
FUEL PRESSURE RELEASE PROCEDURE
(3) Remove protective cap from pressure test port
on the fuel rail (Figs. 5 or 6).
WARNING: THE FUEL SYSTEM IS UNDER CONSTANT
FUEL PRESSURE (EVEN WITH THE ENGINE OFF) OF
APPROXIMATELY 131-269 KPA (19-39 PSI). THIS PRES-
SURE MUST BE RELEASED BEFORE SERVICING ANY
FUEL SUPPLY OR FUEL RETURN SYSTEM COMPO-
NENT.
Fig. 5 Pressure Test Port—4.0L Engine
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FUEL SYSTEM 14 - 5
Fig. 7 Fuel Pressure Regulator—4.0L Engine
Fig. 6 Pressure Test Port—5.2L Engine
(4) Obtain the fuel pressure gauge/hose assembly
from fuel pressure gauge tool set 5069. Remove the
gauge from the hose.
(5) Place one end of hose (gauge end) into an ap-
proved gasoline container.
(6) Place a shop towel under the test port.
(7) To release fuel pressure, screw the other end of
hose onto the fuel pressure test port.
(8) After fuel pressure has been released, remove
the hose from the test port.
(9) Install protective cap to fuel test port.
FUEL SYSTEM PRESSURE TEST
The fuel system is equipped with a vacuum assisted
fuel pressure regulator (Figs. 7 or 8). With engine at
idle speed, system fuel pressure should be approxi-
mately 214 kPa (31 psi) with the vacuum line con-
nected to the regulator. With the vacuum line discon-
nected from the regulator, fuel pressure should be
approximately 269 kPa (39 psi). This is 55-69 kPa
(8-10 psi) higher.
(1) Remove the protective cap at the fuel rail (Figs.
5 or 6). Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from Gauge Set 5069) to test port pressure
fitting on fuel rail (Figs. 9 or 10).
(2) Note pressure gauge reading. Fuel pressure
should be approximately 214 kPa (31 psi) at idle.
(3) Disconnect vacuum line at fuel pressure regula-
tor (Figs. 7 or 8). Note gauge reading. With vacuum
line disconnected, fuel pressure should rise to ap-
proximately 269 kPa (39 psi).
Fuel pressure should be approximately 55-69 kPa
(8-10 psi) higher with vacuum line removed from
regulator. If not, inspect pressure regulator vacuum
line for leaks, kinks or blockage. If vacuum line
Fig. 8 Fuel Pressure Regulator—5.2L Engine
Fig. 9 Fuel Pressure Test Connection—4.0L Engine
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