1995 JEEP YJ Fuel system

FRAME
INDEX
page page
Frame Dimensions........................ 13
Frame Repairs........................... 13
Frame Straightening....................... 13
Fuel Tank Skid Plate....................... 15
General Information....................... 10Generator Splash Shield.................... 13
Safety Precautions and Warnings............. 10
Tow Hooks.............................. 13
Transfer Case Skid Plate.................... 15
SAFETY PRECAUTIONS AND WARNINGS
WARNING: USE EYE PROTECTION WHEN GRIND-
ING OR WELDING METAL, SERIOUS EYE INJURY
CAN RESULT.
BEFORE PROCEEDING WITH FRAME REPAIR IN-
VOLVING GRINDING OR WELDING, VERIFY THAT
VEHICLE FUEL SYSTEM IS NOT LEAKING OR IN
CONTACT WITH REPAIR AREA, PERSONAL INJURY
CAN RESULT.
DO NOT ALLOW OPEN FLAME TO CONTACT
PLASTIC BODY PANELS. FIRE OR EXPLOSION CAN
RESULT.
WHEN WELDED FRAME COMPONENTS ARE RE-
PLACED, 100% PENETRATION WELD MUST BE
ACHIEVED DURING INSTALLATION. IF NOT, DAN-
GEROUS OPERATING CONDITIONS CAN RESULT.
STAND CLEAR OF CABLES OR CHAINS ON
PULLING EQUIPMENT DURING FRAME STRAIGHT-
ENING OPERATIONS, PERSONAL INJURY CAN RE-
SULT.
DO NOT VENTURE UNDER A HOISTED VEHICLE
THAT IS NOT SUPPORTED ON SAFETY STANDS,
PERSONAL INJURY CAN RESULT.
CAUTION: Do not reuse damaged fasteners, quality
of repair would be suspect.
Do not drill holes in top or bottom frame rail
flanges, frame rail failure can result.
Do Not use softer than Grade 3 bolts to replace
production fasteners, loosening or failure can re-
sult.When using heat to straighten frame components
do not exceed 566ÉC (1050ÉF), metal fatigue can re-
sult.
Welding the joints around riveted cross members
and frame side rails can weaken frame
GENERAL INFORMATION
The Jeep YJ (Fig. 1) frame is the structural center
of the vehicle. In addition to supporting the body and
payload, the frame provides a station for the engine.
The vehicle body is attached to the frame with hold-
downs (Fig. 2 and 3).
Fig. 1 JeepÐYJ
13 - 10 YJÐFRAMEJ

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)Ð
COMPONENT DESCRIPTION/SYSTEMOPERATION.......................... 19
MULTI-PORT FUEL INJECTION (MFI)Ð
COMPONENT REMOVAL/INSTALLATION.... 58
MULTI-PORT FUEL INJECTION (MFI)Ð
GENERAL DIAGNOSIS.................. 35
SPECIFICATIONS........................ 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.
TheFuel Systemconsists 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.
TheFuel Delivery Systemconsists of: the electric
fuel pump, fuel filter, fuel tubes/lines/hoses, fuel rail,
fuel injectors and fuel pressure regulator.
AFuel Return Systemis used on all vehicles.
The system consists of: the fuel tubes/lines/hoses that
route fuel back to the fuel tank.
TheFuel Tank Assemblyconsists 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.
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 becovered 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 gasolinecan 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-
JFUEL SYSTEM 14 - 1

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.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 asReformulated 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.
14 - 2 FUEL SYSTEMJ

FUEL DELIVERY SYSTEM
INDEX
page page
Fuel Filter................................ 9
Fuel Pressure Leak Down Test................ 8
Fuel Pressure Release Procedure.............. 6
Fuel Pump Capacity Test.................... 7
Fuel Pump Electrical Control.................. 5Fuel Pump Module......................... 3
Fuel System Pressure Test................... 6
Fuel Tubes/Lines/Hoses and Clamps............ 9
Quick-Connect Fittings..................... 10
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:
²Electric fuel pump
²Fuel pump reservoir
²In-tank fuel filter
²Fuel gauge sending unit
²Fuel 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.
REMOVALÐXJ 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-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).
Fig. 1 Removing Lock RingÐXJ ModelsÐTypical
JFUEL DELIVERY SYSTEM 14 - 3

(8) Remove fuel pump module and O-ring seal.
Discard old O-ring and fuel pump module inlet filter.
DISASSEMBLYÐXJ 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).
ASSEMBLYÐXJ 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.
INSTALLATIONÐXJ 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.(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).
(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.
REMOVALÐYJ 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.
Fig. 2 Fuel Pump ModuleÐXJ ModelsÐ
Disassemble/Assemble
Fig. 3 Fuel Pump ModuleÐXJ ModelsÐInstallation
14 - 4 FUEL DELIVERY SYSTEMJ

(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-
alÐYJ Models.
(4) Remove fuel pump module assembly.
(5) Remove mounting screws. Lift assembly and
gasket out of fuel tank. Discard old gasket (Fig. 4).
(6) Remove and discard fuel pump inlet filter.
DISASSEMBLYÐYJ MODELS
(1) Remove and discard fuel pump inlet filter (Fig.
5).
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.(4) Remove fuel pump top mounting bracket nut
(Fig. 6). Remove fuel pump.
ASSEMBLYÐYJ 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.
INSTALLATIONÐYJ 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 Nzm (18 in. lbs.) torque.
(3) Install fuel tank. Refer to Fuel Tank Installa-
tionÐYJ 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
For an electrical operational description of the fuel
pump, refer to the MFI SystemÐComponent Descrip-
tion/System Operation section of this group. See Au-
tomatic Shutdown (ASD) RelayÐPCM Output.
For the 1995 model year, the ballast resistor and
ballast resistor bypass relay are no longer used to
control the fuel pump circuit.
Fig. 4 Fuel Pump ModuleÐRemove/InstallÐYJ
Models
Fig. 5 Fuel Pump ModuleÐYJ Models
Fig. 6 Fuel Pump Removal/InstallationÐYJ Models
JFUEL DELIVERY SYSTEM 14 - 5

FUEL PRESSURE RELEASE PROCEDURE
WARNING: THE FUEL SYSTEM IS UNDER CON-
STANT FUEL PRESSURE (EVEN WITH THE ENGINE
OFF) OF APPROXIMATELY 131-269 KPA (19-39 PSI).
THIS PRESSURE MUST BE RELEASED BEFORE
SERVICING ANY FUEL SUPPLY OR FUEL RETURN
SYSTEM COMPONENT.
(1) Disconnect negative battery cable.
(2) Remove fuel tank filler neck cap to release fuel
tank pressure.
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.
WARNING: WEAR PROPER EYE PROTECTION
WHEN RELEASING FUEL SYSTEM PRESSURE.
(3) Remove protective cap from pressure test port
on the fuel rail (Fig. 7).
(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 as-
sisted fuel pressure regulator (Fig. 8). With engine atidle 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
disconnected 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 (Fig.
7). Connect the 0-414 kPa (0-60 psi) fuel pressure
gauge (from Gauge Set 5069) to test port pressure fit-
ting on fuel rail (Fig. 9).
(2) Note pressure gauge reading. Fuel pressure
should be approximately 214 kPa (31 psi) at idle.
(3) Disconnect vacuum line (hose) at fuel pressure
regulator (Fig. 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 reg-
ulator. If not, inspect pressure regulator vacuum line
for leaks, kinks or blockage. If vacuum line checks
Fig. 7 Pressure Test PortÐTypical
Fig. 8 Fuel Pressure RegulatorÐTypical
Fig. 9 Fuel Pressure Test ConnectionÐTypical
14 - 6 FUEL DELIVERY SYSTEMJ

OK and fuel pressure does not rise approximately
8-10 psi after disconnecting vacuum line, replace fuel
pressure regulator.
The fuel pressure regulator isnot adjustable.
(4) If fuel pressure exceeds 45 psi, check fuel re-
turn line/tube for kinks or obstructions.
If the previous tests checked good, fuel pump pres-
sure is correct. If pump pressure was low, proceed as
follows:
(5) Release fuel system pressure. Refer to the pre-
vious Fuel Pressure Release Procedure in this group.
(6) Disconnect the 5/16 inch fuel return line quick-
connect fitting at fuel rail. For procedures, refer to
Fuel Tubes/Lines/Hoses and Clamps. Also refer to
Quick-Connect Fittings. These can be found in the
Fuel Delivery System section of this group.
(7) Connect Fuel Line Pressure Test Adapter Tool
number 6539 (5/16 in.) between the disconnected fuel
return line and fuel rail (Fig. 10).
(8) Connect a 0-689 kPa (100 psi) pressure gauge
to Adapter Tool 6539.
WARNING: THE FUEL SYSTEM PRESSURE IN THE
FOLLOWING TEST MAY EXCEED 100 PSI. BEFORE
STARTING TEST, VERIFY GOOD CONNECTIONS AT
ENDS OF ADAPTER TOOL 6539. BE SURE TOOL IS
LOCKED ONTO FUEL RAIL AND FUEL RETURN
LINE. PULL FIRMLY ON ENDS OF TOOL TO VERIFY.
(9) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
(10)MOMENTARILYpinch the rubber hose por-
tion of adapter tool 6539. Pressure should rise to ap-
proximately 75 psi within two (2) seconds.DO NOT
pinch hose for longer than three seconds.
If fuel pump pressure rises to approximately 75 psi
within two seconds, pressure is operating at its max-
imum and is correct.If fuel pump pressure does not rise to approxi-
mately 75 psi within two seconds, proceed as follows:
(11) Release fuel system pressure. Refer to the pre-
vious Fuel Pressure Release Procedure in this group.
(12) Raise and support vehicle.
(13) Disconnect fuel supply line at inlet (fuel tank
side) of fuel filter. Connect Fuel Line Pressure Test
Adapter Tool number 6631 (3/8 in.) between fuel fil-
ter and fuel supply line.
WARNING: THE FUEL SYSTEM PRESSURE IN THE
FOLLOWING TEST MAY EXCEED 100 PSI. BEFORE
STARTING TEST, VERIFY GOOD CONNECTIONS AT
ENDS OF ADAPTER TOOL 6631. BE SURE TOOL IS
LOCKED ONTO FUEL FILTER AND FUEL SUPPLY
LINE. PULL FIRMLY ON ENDS OF TOOL TO VERIFY.
(14) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
MOMENTARILYpinch the rubber hose portion of
adapter tool 6631. Pressure should rise to approxi-
mately 75 psi within two (2) seconds.DO NOTpinch
hose for longer than three seconds.
If fuel pump pressure now rises to approximately
75 psi within two seconds, but this pressure could
not be met at the fuel rail, check for a plugged or re-
stricted fuel filter. Also check the fuel supply line be-
tween fuel filter and fuel rail for kinks or
obstructions. Proceed to the following Fuel Pump Ca-
pacity Test.
FUEL PUMP CAPACITY TEST
Before performing this test, verify fuel pump pres-
sure by performing the previous tests.
(1) Release the fuel system pressure from fuel sys-
tem. Refer to the previous Fuel Pressure Release
Procedure in this group.
(2) Disconnect the fuel supply line at fuel rail near
pressure regulator. For procedures, refer to Fuel
Tubes/Lines/Hoses and Clamps. Also refer to Quick-
Connect Fittings. These can be found in the Fuel De-
livery System section of this group.
(3) Connect Fuel Line Pressure Test Adapter Tool
number 6631 (3/8 in.) into the disconnected fuel sup-
ply line. Insert the other end of tool 6631 into an ap-
proved gasoline container.
(4) To activate the fuel pump and pressurize the
system, obtain the DRB scan tool. Refer to the appro-
priate Powertrain Diagnostic Procedures service
manual for DRB operation.
A good fuel pump will deliver at least 1 liter of fuel
per minute.
Fig. 10 Adapter ToolÐTypical Connection
JFUEL DELIVERY SYSTEM 14 - 7