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FUEL SYSTEM
14 - 1
FUEL SYSTEM
CONTENTS
page
page
ACCELERATOR PEDAL AND THROTTLE CABLE . 17
FUEL DELIVERY SYSTEM . . . . . . . . . . . . . . . . . . 3
FUEL TANKS . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 1
MULTI-PORT FUEL INJECTION (MFI)—
COMPONENT DESCRIPTION/SYSTEM
OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . .
MULTI-PORT FUEL INJECTION (MFI)—
COMPONENT REMOVAL/INSTALLATION . . . .
MULTI-PORT FUEL INJECTION (MFI)—
GENERAL DIAGNOSIS . . . . . . . . . . . . . . . . . .
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . .
19
58
35
67
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of the alphabetical desig-
nations is included 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 a fuel fil-
ter. 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 fill and vent hoses, 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.
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
additives will help improve fuel economy, reduce
emissions and maintain vehicle performance.
Poor quality gasoline
can cause problems such
as hard starting, stalling and stumble. If you experi-
ence 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.
METHANOL
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.
Methanol (Methyl or Wood Alcohol) is used in a va-
riety of concentrations blended with unleaded gaso-
FUEL USAGE STATEMENT
Your vehicle was designed to meet all emission reg-
ulations 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 harm-
ful. However,
continued heavy knock at high
speeds can cause damage and should be re-
ported to your dealer immediately.
Engine dam-
age as a result of heavy knock operation may not be
14 - 2
FUEL SYSTEM
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CLEAN AIR GASOLINE
Many gasolines are now being blended that con-
tribute 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 lev-
els are high, gasolines are being treated with oxygen-
ated 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.
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/gas-
oline 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
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.
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FUEL DELIVERY SYSTEM
INDEX
page
Fuel
Fuel
Fuel
Fuel
Fuel
Filter . . . . . . . . . . . . . . . . . .
Pressure Leak Down Test . .
Pressure Release Procedure
Pump Capacity Test . . . . . .
Pump Electrical Control . . . .
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6
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5
FUEL DELIVERY SYSTEM
14 - 3
page
Fuel Pump Module . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fuel System Pressure Test . . . . . . . . . . . . . . . . . . . 6
Fuel Tubes/Lines/Hoses and Clamps . . . . . . . . . . . . 9
Quick-Connect Fittings . . . . . . . . . . . . . . . . . . . . . 10
LEASED. REFER TO THE FUEL PRESSURE RE-
LEASE PROCEDURE IN THIS GROUP.
WARNING: EXTINGUISH ALL TOBACCO SMOKING
PRODUCTS BEFORE SERVICING THE FUEL SYS-
TEM. KEEP OPEN FLAME AWAY FROM FUEL SYS-
TEM COMPONENTS.
(1) Remove fuel filler cap. Perform the Fuel Pres-
sure Release Procedure as outlined in this group.
(2) Disconnect negative battery cable.
(3) Using an approved portable gasoline siphon/
storage tank, drain fuel tank until fuel level is below
one quarter (1/4) full.
(4) Raise and support vehicle.
WARNING: WRAP SHOP TOWELS AROUND FUEL
HOSES TO ABSORB ANY FUEL SPILLAGE DURING
FUEL TANK REMOVAL.
(5) Disconnect fuel vent supply and return tubes
from fittings on fuel pump module.
(6) Disconnect fuel pump module electrical harness
connector from main harness.
(7) Using a brass punch and hammer, remove fuel
pump module lock ring by carefully tapping it coun-
terclockwise (Fig. 1).
FUEL PUMP MODULE
The fuel pump module is installed in the top of the
fuel tank. The fuel pump module contains the follow-
ing components:
•
Electric fuel pump
•
Fuel pump reservoir
•
In-tank fuel filter
•
Fuel gauge sending unit
•
Fuel supply and return tube connections
The fuel pump used on all vehicles is a turbine
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 ap-
plied from a spring. When the pump is operating,
fuel pressure overcomes spring pressure and forces
the ball off its seat, allowing fuel to flow. When the
pump is not operating, spring pressure forces the ball
back against the seat preventing fuel backflow
through the pump.
Fuel system pressure is maintained at approxi-
mately 214 kPa (31 psi). This is when the pump is
operating and vacuum is supplied to the fuel pres-
sure regulator. If vacuum is not supplied to the pres-
sure regulator, fuel pressure will be approximately
55-69 kPa (8-10 psi) higher. This may be due to a
broken or clogged vacuum line. When the fuel pump
is not operating, fuel system pressure of 131-269 kPa
(19-39 psi) is maintained for approximately 2 to 6
hours. This is done by the fuel pump outlet check
valve and the vacuum assisted fuel pressure regula-
tor.
REMOVAL—XJ MODELS
The fuel pump/gauge sender unit assembly can be
removed from the fuel tank without removing the
tank from the vehicle.
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-
Fig. 1 Removing Lock Ring—XJ Models—Typical
14 - 4
FUEL DELIVERY SYSTEM
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(2) Install fuel pump module assembly and new O-
ring seal. The rubber stopper on the end of the fuel
return tube of the assembly must be inserted into the
cup in the fuel tank reservoir (Fig. 3).
(8) Remove fuel pump module and O-ring seal.
Discard old O-ring and fuel pump module inlet filter.
DISASSEMBLY—XJ MODELS
(1) Remove and discard fuel pump inlet filter.
The wire terminals to the fuel pump motor are dif-
ferent in size and cannot be connected to the wrong
terminal.
(2) Disconnect fuel pump terminal wires.
(3) Remove fuel pump outlet hose and clamp. Re-
place the hose if it shows any signs of fatigue or fail-
ure.
(4) Remove fuel pump top mounting bracket nut.
Remove fuel pump (Fig. 2).
Fig. 3 Fuel Pump Module—XJ Models—Installation
(3) Using a brass punch and a hammer, install lock
ring. Carefully tap lock ring clockwise until it seats
against stop on fuel tank.
(4) Connect fuel supply and return hoses to fittings
on fuel pump module. Tighten hose clamps.
(5) Connect fuel pump module electrical harness
connector to main harness connector.
(6) Lower vehicle.
(7) Fill fuel tank. Install fuel tank cap.
(8) Connect negative battery cable.
(9) Start vehicle and inspect for leaks.
Fig. 2 Fuel Pump Module—XJ Models—
Disassemble/Assemble
ASSEMBLY—XJ MODELS
Whenever the fuel pump is replaced, the fuel pump
inlet filter (sock) must also be replaced.
(1) Place fuel pump top mounting bracket over top
of pump.
(2) Position fuel pump into lower bracket. Slide
stud of top bracket through hole in fuel pump side
bracket. Tighten fuel pump top mounting nut.
(3) Install new fuel pump outlet hose. Secure with
new clamps.
(4) Connect wire terminals to motor.
(5) Install new fuel pump inlet filter.
REMOVAL—YJ MODELS
The fuel tank must be removed to remove the fuel
pump module.
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.
WARNING: EXTINGUISH ALL TOBACCO SMOKING
PRODUCTS BEFORE SERVICING THE FUEL SYS-
TEM. KEEP OPEN FLAME AWAY FROM FUEL SYS-
TEM COMPONENTS.
(1) Remove negative battery cable.
INSTALLATION—XJ MODELS
Whenever the fuel pump is replaced, the fuel
pump inlet filter must also be replaced.
(1) Install new fuel pump inlet filter onto fuel
pump.
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(2) Remove fuel filler cap. Perform the Fuel Pres-
sure Release Procedure as outlined in this group.
(3) Remove fuel tank. Refer to Fuel Tank Remov-
al—YJ Models.
(4) Remove fuel pump module assembly.
(5) Remove mounting screws. Lift assembly and
gasket out of fuel tank. Discard old gasket (Fig. 4).
FUEL DELIVERY SYSTEM
14 - 5
(4) Remove fuel pump top mounting bracket nut
(Fig. 6). Remove fuel pump.
Fig. 6 Fuel Pump Removal/Installation—YJ Models
ASSEMBLY—YJ MODELS
Whenever the fuel pump is replaced, the fuel pump
inlet filter (sock) must also be replaced.
(1) Place fuel pump top mounting bracket over top
of pump.
(2) Position fuel pump into lower bracket. Slide
stud of top bracket through hole in fuel pump side
bracket. Tighten fuel pump top mounting nut.
(3) Install new fuel pump outlet hose. Secure with
new clamps.
(4) Connect wire terminals to motor.
(5) Install new fuel pump inlet filter.
Fig. 4 Fuel Pump Module—Remove/Install—YJ
Models
(6) Remove and discard fuel pump inlet filter.
DISASSEMBLY—YJ MODELS
(1) Remove and discard fuel pump inlet filter (Fig.
5).
INSTALLATION—YJ MODELS
(1) Install a new fuel pump inlet filter.
(2) Install fuel pump module assembly with a new
gasket between the assembly and tank. Tighten
mounting screws to 2 N m (18 in. lbs.) torque.
(3) Install fuel tank. Refer to Fuel Tank Installa-
tion—YJ Models.
(4) Fill fuel tank. Install fuel tank cap.
(5) Install negative battery cable.
(6) Start vehicle and check for leaks.
FUEL PUMP ELECTRICAL CONTROL
Fig. 5 Fuel Pump Module—YJ Models
The wire terminals to the fuel pump motor are dif-
ferent in size and cannot be connected to the wrong
terminal.
(2) Disconnect fuel pump terminal wires from
pump.
(3) Remove fuel pump outlet hose and clamp (Fig.
6). Replace the hose if it shows any signs of fatigue
or failure.
For an electrical operational description of the fuel
pump, refer to the MFI System—Component Descrip-
tion/System Operation section of this group. See Au-
tomatic Shutdown (ASD) Relay—PCM Output.
For the 1995 model year, the ballast resistor and
ballast resistor bypass relay are no longer used to
control the fuel pump circuit.

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