ZJ FUEL SYSTEM 14 - 1 FUEL SYSTEM CONTENTS page pageACCELERATOR PEDAL AND THROTTLE CABLE MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 CYL. ENGINE—GENERAL DIAGNOSIS . . . . . 29FUEL DELIVERY SYSTEM . . . . . . . . . . . . . . . . . . 3 MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8FUEL TANKS . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ENGINE—COMPONENT DESCRIPTION/GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 1 SYSTEM OPERATION . . . . . . . . . . . . . . . . . . . 53MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8 CYL. ENGINE—COMPONENT DESCRIPTION/ ENGINE—COMPONENT REMOVAL/ SYSTEM OPERATION . . . . . . . . . . . . . . . . . . . 17 INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 85MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8 CYL. ENGINE—COMPONENT REMOVAL/ ENGINE—GENERAL DIAGNOSIS . . . . . . . . . . 66 INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 45 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 95 GENERAL INFORMATION Throughout this group, references are made to par- tive Control System is found in Group 25, Emissionticular vehicle models by alphabetical designation or Control Systems.by the particular vehicle nameplate. A chart showinga breakdown of the alphabetical designations is in- FUEL USAGE STATEMENTcluded in the Introduction section at the beginning of Your vehicle was designed to meet all emission reg-this manual. ulations and provide excellent fuel economy using The Fuel System consists of: the fuel tank, an high quality unleaded gasoline. Only use unleadedelectric (fuel tank mounted) fuel pump, a fuel pres- gasolines having a minimum posted octane of 87.sure regulator, fuel filter, sensors, switches and pow- If your vehicle develops occasional light sparkertrain control module (PCM). It also consists of fuel knock (ping) at low engine speeds, this is not harm-tubes/lines/hoses, vacuum hoses, throttle body, fuel ful. However, continued heavy knock at highrail and fuel injectors. speeds can cause damage and should be re- The Fuel Delivery System consists of: the electric ported to your dealer immediately. Engine dam-fuel pump, a frame mounted fuel filter, fuel tubes/ age as a result of heavy knock operation may not belines/hoses, fuel rail, fuel injectors and fuel pressure covered by the new vehicle warranty.regulator. In addition to using unleaded gasoline with the A Fuel Return System is used on all models witheither a 4.0L or 5.2L engine. A separate fuel return proper octane rating, those that contain deter-line from the engine to the tank is no longer used on gents, corrosion and stability additives are rec-any 4.0L or 5.2L engine. Excess fuel is returned ommended. Using gasolines that have thesethrough the fuel pump module and back into the fuel additives will help improve fuel economy, reducetank through the fuel pressure regulator. The fuel emissions and maintain vehicle performance.pressure regulator is located in the fuel tank within Poor quality gasoline can cause problems suchthe fuel pump module. as hard starting, stalling and stumble. If you experi- The Fuel Tank Assembly consists of: the fuel ence these problems, use another brand of gasolinetank, filler tube, fuel gauge sending unit/electric fuel before considering service for the vehicle.pump module, a fuel pressure regulator mounted tothe fuel pump module, a pressure relief/rollover valve GASOLINE/OXYGENATE BLENDSand a pressure-vacuum filler cap. Some fuel suppliers blend unleaded gasoline with Also to be considered part of the fuel system is the materials that contain oxygen such as alcohol, MTBEEvaporation Control System. This is designed to and ETBE. The type and amount of oxygenate usedreduce the emission of fuel vapors into the atmo- in the blend is important. The following are generallysphere. The description and function of the Evapora- used in gasoline blends:
14 - 2 FUEL SYSTEM ZJETHANOL MTBE/ETBE Ethanol (Ethyl or Grain Alcohol) properly blended, Gasoline and MTBE (Methyl Tertiary Butyl Ether)is used as a mixture of 10 percent ethanol and 90 blends are a mixture of unleaded gasoline and up topercent gasoline. Gasoline with ethanol may be 15 percent MTBE. Gasoline and ETBE (Ethyl Ter-used in your vehicle. tiary Butyl Ether) are blends of gasoline and up to 17 percent ETBE. Gasoline blended with MTBE orMETHANOL ETBE may be used in your vehicle.CAUTION: DO NOT USE GASOLINES CONTAINING CLEAN AIR GASOLINEMETHANOL. Use of methanol/gasoline blends may re- Many gasolines are now being blended that con-sult in starting and driveability problems. In addition, tribute to cleaner air, especially in those areas of thedamage may be done to critical fuel system compo- country where air pollution levels are high. Thesenents. new blends provide a cleaner burning fuel and some Methanol (Methyl or Wood Alcohol) is used in a va- are referred to as Reformulated Gasoline.riety of concentrations blended with unleaded gaso- In areas of the country where carbon monoxide lev-line. You may encounter fuels containing 3 percent or els are high, gasolines are being treated with oxygen-more methanol along with other alcohols called cosol- ated materials such as MTBE, ETBE and ethanol.vents. Chrysler Corporation supports these efforts toward Problems that are the result of using methanol/gas- cleaner air and recommends that you use these gaso-oline blends are not the responsibility of Chrysler lines as they become available.Corporation. They may not be covered by the vehiclewarranty.
ZJ FUEL DELIVERY SYSTEM 14 - 3 FUEL DELIVERY SYSTEM INDEX page pageFuel Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Fuel Pump Module . . . . . . . . . . . . . . . . . . . . . . . . . 3Fuel Line with Latch Clip . . . . . . . . . . . . . . . . . . . . 10 Fuel System Pressure Release Procedure . . . . . . . . 4Fuel Pressure Leak Down Test . . . . . . . . . . . . . . . . 6 Fuel System Pressure Test . . . . . . . . . . . . . . . . . . . 5Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . . 4 Fuel Tubes/Lines/Hoses and Clamps . . . . . . . . . . . . 7Fuel Pump Capacity Test . . . . . . . . . . . . . . . . . . . . 5 Quick-Connect Fittings . . . . . . . . . . . . . . . . . . . . . . 7Fuel Pump Electrical Control . . . . . . . . . . . . . . . . . . 4FUEL PUMP MODULE The fuel pump module is not serviceable. If the The fuel pump module is installed in the top of the electric fuel pump or the fuel pressure regulatorfuel tank (Fig. 1). The fuel pressure regulator is a needs replacement, the complete fuel pump modulepart of the fuel pump module assembly and is no must be replaced.longer mounted to the fuel rail on either engine. Thefuel pump module contains the following components: REMOVAL• Electric fuel pump WARNING: THE FUEL SYSTEM IS UNDER A CON-• Fuel pressure regulator STANT PRESSURE EVEN WITH THE ENGINE OFF.• Fuel pump reservoir BEFORE SERVICING THE FUEL PUMP MODULE,• In-tank fuel filter THE FUEL SYSTEM PRESSURE MUST BE RE-• Fuel gauge sending unit LEASED. REFER TO THE FUEL SYSTEM PRES-• Fuel supply line (tube) connection SURE RELEASE PROCEDURE IN THIS GROUP. (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 Location The fuel pump used on all models is driven by apermanent magnet 12 volt electric motor that is im-mersed in the fuel tank. The electrical pump is inte-gral with the fuel sender unit. The pump/senderassembly is installed inside the fuel tank. The fuel pump has a check valve at the outlet endthat consists of a ball held against a seat by force ap- Fig. 2 Top View of Fuel Pump Module—Typicalplied from a spring. When the pump is operating,fuel pressure overcomes spring pressure and forces (3) Remove module from fuel tank.the ball off its seat, allowing fuel to flow. When thepump is not operating, spring pressure forces the ball INSTALLATIONback against the seat preventing fuel backflow CAUTION: Whenever the fuel pump module is ser-through the pump. viced, the rubber gasket must be replaced.
14 - 4 FUEL DELIVERY SYSTEM ZJ (1) Clean the fuel tank at the module opening. (2) Using a new gasket on the fuel tank (Fig. 3),position fuel pump module into opening in fuel tank.Refer to figure 2 for rotational position. Fig. 4 Fuel Pressure Regulator Location Fuel is supplied to the regulator by the electric fuel pump. The fuel pump also contains a check valve to maintain some fuel pressure at the fuel injectors Fig. 3 Rubber Gasket when the engine is not operating. This will help to start the engine. (3) Tighten locknut. If fuel pressure at the pressure regulator exceeds (4) Install fuel tank. Refer to Fuel Tank Installa- 269-283 kPa (39-41 psi), an internal diaphragmtion in this group. closes and excess fuel pressure is routed back into the fuel tank through the pressure regulator. A sep-FUEL PUMP REPLACEMENT arate fuel return line to the engine is no longer used The electric fuel pump is not serviceable. If the fuel with any 4.0L or 5.2L engine.pump needs replacement, the complete fuel pumpmodule must be replaced. Refer to the previous pro- REMOVAL/INSTALLATIONcedure. The fuel pressure regulator is not serviced sepa- rately. If the pressure regulator needs replacement,FUEL GAUGE SENDING UNIT REPLACEMENT the fuel pump module must be replaced. Refer to The fuel gauge sending unit is not serviceable. If Fuel Pump Module Removal/Installation for proce-the unit needs replacement, the complete fuel pump dures.module must be replaced. FUEL PUMP ELECTRICAL CONTROLFUEL PRESSURE REGULATOR The powertrain control module (PCM) computer en- ergizes the fuel pump through the fuel pump relay.ALL ENGINES Battery voltage is applied to the relay from the igni- A fuel pressure regulator is used with all engines. tion switch. The coil in the relay is energized when aIt is mounted inside of the fuel pump module (Fig. 4) ground is provided by the PCM. The relay is locatedand is suspended in fuel. in the power distribution center (PDC) next to the The vacuum assisted fuel pressure regulator battery (Fig. 5). For location of relay within the PDC,located on the fuel rail is no longer used on the refer to label under PDC cover.4.0L or 5.2L engine. Also refer to either of the MFI System—Component Fuel Pressure Regulator Operation: The pres- Description/System Operation sections of this group.sure regulator is a mechanical device that is not con- See Automatic Shutdown (ASD) Relay—PCM Output.trolled by engine vacuum or by the powertraincontrol module (PCM). FUEL SYSTEM PRESSURE RELEASE PROCEDURE The regulator is calibrated to maintain a constant WARNING: THE FUEL SYSTEM IS UNDER CON-pressure at the fuel pump module outlet fitting of STANT FUEL PRESSURE EVEN WITH THE ENGINE269-283 kPa (39-41 psi). System operating pressure OFF. THIS PRESSURE MUST BE RELEASED BE-at the fuel injectors, as measured at the fuel rail test FORE SERVICING ANY FUEL SUPPLY SYSTEMport is 255-283 kPa (39 psi Ϯ 2 psi). The regulator COMPONENT.contains a diaphragm, calibrated springs and a fuelreturn valve. (1) Disconnect negative battery cable.
ZJ FUEL DELIVERY SYSTEM 14 - 5 Fig. 7 Pressure Test Port Location—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. Fig. 5 Power Distribution Center (6) Place a shop towel under the test port. (2) Remove fuel tank filler neck cap to release fuel (7) To release fuel pressure, screw the other end oftank pressure. hose onto the fuel pressure test port. (8) After fuel pressure has been released, removeWARNING: DO NOT ALLOW FUEL TO SPILL ONTO the hose from the test port.THE ENGINE INTAKE OR EXHAUST MANIFOLDS. (9) Install protective cap to fuel test port.PLACE SHOP TOWELS UNDER AND AROUND THEPRESSURE PORT TO ABSORB FUEL WHEN THE FUEL SYSTEM PRESSURE TESTPRESSURE IS RELEASED FROM THE FUEL RAIL. The vacuum assisted fuel pressure regulator located on the fuel rail is no longer used on theWARNING: WEAR PROPER EYE PROTECTION 4.0L or 5.2L engine.WHEN RELEASING FUEL SYSTEM PRESSURE. Fuel systems on the 4.0L and 5.2L engines are equipped with a fuel tank module mounted, fuel (3) Remove protective cap from pressure test port pressure regulator (Fig. 4). The fuel pressure regula-on the fuel rail (Figs. 6 or 7). tor is a mechanical device that is not controlled by the powertrain control module (PCM) or by engine vacuum. With engine at idle speed, system fuel pressure should be 255-283 kPa (39 psi Ϯ 2 psi). (1) Remove the protective cap at the fuel rail (Figs. 6 or 7). Connect the 0-414 kPa (0-60 psi) fuel pres- sure gauge (from Gauge Set 5069) to test port pres- sure fitting on fuel rail (Fig. 8). (2) Note pressure gauge reading. Fuel pressure should be 255-283 kPa (39 psi Ϯ 2 psi) at idle. (3) If pressure is at O psi, connect DRB scan tool and refer to operating instructions in the appropriate Powertrain Diagnostics Procedures service manual. If operating pressure is above 41 psi, the electric fuel pump is OK, but the fuel pressure regulator if defective. Replace fuel pump module assembly. Fig. 6 Pressure Test Port Location—4.0L Engine FUEL PUMP CAPACITY TEST Before performing this test, verify fuel pump pres- sure by performing the previous tests.
14 - 6 FUEL DELIVERY SYSTEM ZJ Fig. 9 Connecting Adapter Tool—Typical (3) Connect the 0-414 kPa (0-60 psi) fuel pressure test gauge (from Gauge Set 5069) to the test port on either tool 6631 or 6539. The fittings on both tools must be in good condition and free from any Fig. 8 Typical Fuel Pressure Test Connection small leaks before performing the proceeding test. (1) Release the fuel system pressure from fuel sys- (4) Start engine and bring to normal operatingtem. Refer to the previous Fuel System Pressure Re- temperature.lease Procedure in this group. (5) Observe test gauge. Normal operating pressure (2) Disconnect the fuel supply line at the fuel rail. at the fuel rail test port should be 255-283 kPa (39Refer to Fuel Tubes/Lines/Hoses and Clamps in this psi Ϯ 2 psi).section of the group for procedures. (6) Shut engine off. (3) Connect Fuel Line Pressure Test Adapter Tool (7) Pressure should not fall below 24 psi for fivenumber 6631 (3/8 in.) into the disconnected fuel sup- minutes.ply line. Insert the other end of tool 6631 into an ap- (8) If pressure falls below 24 psi, it must deter-proved gasoline container. mined if a fuel injector, the fuel module mounted fuel (4) To activate the fuel pump and pressurize the pressure regulator or a fuel tube/line is leaking.system, obtain the DRB scan tool. Refer to the appro- (9) Again, start engine and bring to normal operat-priate Powertrain Diagnostic Procedures service ing temperature.manual for DRB operation. (10) Shut engine off. (5) A good fuel pump will deliver at least 1 liter of (11) Checking for fuel injector leakage: Clampfuel per minute. off the rubber hose portion of either tool 6539 or 6631 between the disconnected fuel tube (line) and testFUEL PRESSURE LEAK DOWN TEST port inlet. If pressure now holds at or above 24 psi, aENGINE OFF fuel injector or the fuel rail is leaking. Checking for fuel pump module or fuel tube Abnormally long periods of cranking to restart a leakage: Clamp off the rubber hose portion of eitherhot engine that has been shut down for a short pe- tool 6539 or 6631 between the fuel rail and test portriod of time may be caused by: inlet. If pressure now holds at or above 24 psi, a leak• Fuel pressure bleeding past a fuel injector(s). can be found at a fuel tube/line. If no leaks are found• Fuel pressure bleeding past the check valve in the at fuel tubes or lines, replace the fuel pump module.fuel pump module. (1) Disconnect the fuel inlet line at fuel rail. Refer MECHANICAL MALFUNCTIONSto Fuel Tubes/Lines/Hoses and Clamps in this section Mechanical malfunctions are more difficult to diag-of the group for procedures. nose with this system. The powertrain control mod- (2) Connect Fuel Line Pressure Test Adapter Tool ule (PCM) has been programmed to compensate fornumber 6539 (5/16 in.), or Adapter Tool number 6631 some mechanical malfunctions such as incorrect cam(3/8 in.) between the disconnected fuel line and fuel timing, vacuum leaks, etc. If engine performancerail (Fig. 9). problems are encountered and diagnostic trouble
ZJ FUEL DELIVERY SYSTEM 14 - 7codes are not displayed, the problem may be mechan- (1) Place fuel filter in retaining strap with theical rather than electronic. marked ends in the correct position. (2) Install retaining strap bolt. Tighten to 7 N⅐mFUEL FILTER (66 in. lbs.) torque. The fuel filter protects the fuel injectors from dirt, (3) Install fuel lines to filter. Refer to Fuel Tubes/water and other foreign matter. The filter is located Lines/Hoses and Clamps in this group. Also refer tounder the vehicle near the front of fuel tank (Fig. Quick-Connect Fittings in this group for procedures.10). Replace fuel filter at intervals specified in the (4) Lower vehicle.Lubrication and Maintenance Schedule chart found (5) Connect negative battery cable.in Group 0, Lubrication and Maintenance. (6) Start engine and check for leaks.REMOVAL FUEL TUBES/LINES/HOSES AND CLAMPS Also refer to the proceeding section on Quick-Con-WARNING: THE FUEL SYSTEM IS UNDER CON- nect Fittings.STANT FUEL PRESSURE EVEN WITH THE ENGINEOFF. THIS PRESSURE MUST BE RELEASED BE- WARNING: THE FUEL SYSTEM IS UNDER A CON-FORE SERVICING THE FUEL FILTER. STANT PRESSURE EVEN WITH THE ENGINE OFF. BEFORE SERVICING ANY FUEL SYSTEM HOSES, (1) Disconnect negative battery cable. Remove fuel FITTINGS OR LINES, THE FUEL SYSTEM PRES-filler cap. SURE MUST BE RELEASED. REFER TO THE FUEL (2) Release fuel system pressure. Refer to the pre- SYSTEM PRESSURE RELEASE PROCEDURE INvious Fuel System Pressure Release Procedure in THIS GROUP.this section. (3) Raise and support vehicle. Inspect all hose connections such as clamps, cou- (4) Place shop towels under fuel filter. plings and fittings to make sure they are secure and (5) Disconnect fuel lines at filter. Refer to Quick- leaks are not present. The component should be re-Connect Fittings in this group for procedures. placed immediately if there is any evidence of degra- dation that could result in failure. Never attempt to repair a plastic fuel line/tube. Re- place as necessary. Avoid contact of any fuel tubes/hoses with other ve- hicle components that could cause abrasions or scuff- ing. Be sure that the plastic fuel lines/tubes are properly routed to prevent pinching and to avoid heat sources. 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. The hose clamps used to secure rubber hoses on fuel injected vehicles are of a special rolled edge con- struction. 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 Fig. 10 Fuel Filter hoses and cause high-pressure fuel leaks. (6) Remove retaining strap mounting bolt (Fig. 10). Use new original equipment type hose clamps. (7) Remove filter retaining strap (Fig. 10). Tighten hose clamps to 1 N⅐m (15 in. lbs.) torque. (8) Remove filter from mounting bracket. QUICK-CONNECT FITTINGSINSTALLATION Also refer to the previous Fuel Tubes/Lines/Hoses and Clamps section.CAUTION: The ends of the fuel filter are marked for Different types of quick-connect fittings are used tocorrect installation. Install filter with the end marked attach various fuel system components. These are: aIN towards fuel tank and the end marked OUT to- single-tab type, a two-tab type or a plastic retainerwards engine. ring type.
14 - 8 FUEL DELIVERY SYSTEM ZJSINGLE-TAB TYPE This type of fitting is equipped with a single pulltab (Fig. 11). The tab is removable. After the tab isremoved, the quick-connect fitting can be separatedfrom the fuel system component. Fig. 12 Disconnecting Single-Tab Type Fitting Fig. 11 Single-Tab Type FittingCAUTION: The interior components (o-rings, spac-ers) of this type of quick-connect fitting are not ser-viced separately, but new pull tabs are available. Donot attempt to repair damaged fittings or fuel lines/tubes. If repair is necessary, replace the completefuel tube assembly.WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINE OFF.BEFORE SERVICING ANY FUEL SYSTEM HOSES, Fig. 13 Removing Pull TabFITTINGS OR LINES, THE FUEL SYSTEM PRES-SURE MUST BE RELEASED. REFER TO THE FUEL (7) Disconnect the quick-connect fitting from theSYSTEM PRESSURE RELEASE PROCEDURE IN fuel system component being serviced.THIS GROUP. (8) Inspect the quick-connect fitting body and fuel system component for damage. Replace as necessary. (9) Prior to connecting the quick-connect fitting toDISCONNECTION/CONNECTION component being serviced, check condition of fitting (1) Disconnect negative battery cable from battery. and component. Clean the parts with a lint-free (2) Perform the fuel pressure release procedure. cloth. Lubricate them with clean engine oil.Refer to the Fuel System Pressure Release Procedure (10) Insert the quick-connect fitting into the fuelin this section. tube or fuel system component until the built-on stop (3) Clean the fitting of any foreign material before on the fuel tube or component rests against back ofdisassembly. fitting. (4) Press the release tab on the side of fitting to re- (11) Obtain a new pull tab. Push the new tab downlease pull tab (Fig. 11). until it locks into place in the quick-connect fitting. (12) Verify a locked condition by firmly pulling onCAUTION: If this release tab is not pressed prior to fuel tube and fitting.releasing the pull tab, the pull tab will be damaged. (13) Connect negative cable to battery. (5) While pressing the release tab on the side of (14) Start engine and check for leaks.the fitting, use a screwdriver to pry up the pull tab(Fig. 12). (6) Raise the pull tab until it separates from thequick-connect fitting (Fig. 13). Discard the old pulltab.
ZJ FUEL DELIVERY SYSTEM 14 - 9TWO-TAB TYPE FITTING (5) Inspect the quick-connect fitting body and com- This type of fitting is equipped with tabs located on ponent for damage. Replace as necessary.both sides of the fitting (Fig. 14). These tabs are sup-plied for disconnecting the quick-connect fitting from CAUTION: When the quick-connect fitting was dis-component being serviced. connected, the plastic retainer will remain on the component being serviced. If this retainer must be removed, very carefully release the retainer from the component with two small screwdrivers. After removal, inspect the retainer for cracks or any dam- age. (6) Prior to connecting the quick-connect fitting to component being serviced, check condition of fitting and component. Clean the parts with a lint-free cloth. Lubricate them with clean engine oil. (7) Insert the quick-connect fitting to the compo- nent being serviced and into the plastic retainer. When a connection is made, a click will be heard. (8) Verify a locked condition by firmly pulling on fuel tube and fitting. (9) Connect negative cable to battery.Fig. 14 Typical Two-Tab Type Quick-Connect Fitting (10) Start engine and check for leaks.CAUTION: The interior components (o-rings, spac- PLASTIC RETAINER RING TYPE FITTINGers) of this type of quick-connect fitting are not ser- This type of fitting can be identified by the use of aviced separately, but new plastic retainers are full-round plastic retainer ring (Fig. 15) usually blackavailable. Do not attempt to repair damaged fittings in color.or fuel lines/tubes. If repair is necessary, replacethe complete fuel tube assembly.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 FUELSYSTEM PRESSURE RELEASE PROCEDURE INTHIS GROUP.DISCONNECTION/CONNECTION (1) Disconnect negative battery cable from the bat-tery. (2) Perform the fuel pressure release procedure.Refer to the Fuel System Pressure Release Procedurein this section. (3) Clean the fitting of any foreign material beforedisassembly. (4) To disconnect the quick-connect fitting, squeezethe plastic retainer tabs against the sides of the Fig. 15 Plastic Retainer Ring Type Fittingquick-connect fitting with your fingers. Tool use isnot required for removal and may damage plastic re- CAUTION: The interior components (o-rings, spac-tainer. Pull the fitting from the fuel system compo- ers, retainers) of this type of quick-connect fittingnent being serviced. The plastic retainer will remain are not serviced separately. Do not attempt to repairon the component being serviced after fitting is dis- damaged fittings or fuel lines/tubes. If repair is nec-connected. The o-rings and spacer will remain in the essary, replace the complete fuel tube assembly.quick-connect fitting connector body.
14 - 10 FUEL DELIVERY SYSTEM ZJWARNING: THE FUEL SYSTEM IS UNDER A CON- (4) Pry up on the latch clip with a screwdriverSTANT PRESSURE EVEN WITH THE ENGINE OFF. (Fig. 17).BEFORE SERVICING ANY FUEL SYSTEM HOSES,FITTINGS OR LINES, THE FUEL SYSTEM PRES-SURE MUST BE RELEASED. REFER TO THE FUELSYSTEM PRESSURE RELEASE PROCEDURE INTHIS GROUP.DISCONNECTION/CONNECTION (1) Disconnect negative battery cable from the bat-tery. (2) Perform the fuel pressure release procedure.Refer to the Fuel System Pressure Release Procedurein this section. (3) Clean the fitting of any foreign material beforedisassembly. (4) To release the fuel system component from thequick-connect fitting, firmly push the fitting towards Fig. 16 Latch Clip Location—Typicalthe component being serviced while firmly pushingthe plastic retainer ring into the fitting (Fig. 15).With the plastic ring depressed, pull the fitting fromthe component. The plastic retainer ring must bepressed squarely into the fitting body. If this re-tainer is cocked during removal, it may be dif-ficult to disconnect fitting. Use an open-endwrench on the shoulder of the plastic retainerring to aid in disconnection. After disconnection, the plastic retainer ring willremain with the quick-connect fitting connector body. (5) Inspect fitting connector body, plastic retainerring and fuel system component for damage. Replaceas necessary. (6) Prior to connecting the quick-connect fitting tocomponent being serviced, check condition of fittingand component. Clean the parts with a lint-freecloth. Lubricate them with clean engine oil. Fig. 17 Latch Clip Removal—Typical (7) Insert the quick-connect fitting into the compo-nent being serviced until a click is felt. (8) Verify a locked condition by firmly pulling onfuel tube and fitting. (9) Connect negative battery cable to battery. (10) Start engine and check for leaks.FUEL LINE WITH LATCH CLIPDISCONNECTION/CONNECTION AT FUEL RAIL A latch clip is used to secure the fuel line to thefuel rail on the 5.2L V-8 engine (Fig. 16). A specialtool will be necessary to separate the fuel line fromthe fuel rail after the latch clip is removed. (1) Disconnect the negative battery cable from bat-tery. (2) Perform the fuel pressure release procedure. Fig. 18 Fuel Line Disconnection—TypicalRefer to the Fuel System Pressure Release Procedurein this section. (5) Slide the latch clip toward the fuel rail while (3) Clean the fitting of any foreign material before lifting with the screwdriver.disassembly. (6) Remove the latch clip from fuel rail.
ZJ FUEL DELIVERY SYSTEM 14 - 11 (7) Insert special fuel line removal tool (Snap-On (11) Insert the fuel line onto the fuel rail until anumber FIH 9055-1 or equivalent) into the fuel line click is felt.(Fig. 18). Use this tool to release the locking fingers (12) Verify a locked condition by firmly pulling onin the end of the line. fuel line and fitting (15-30 lbs.). (8) With the special tool still inserted, pull the fuel (13) Install latch clip (snaps into position). If theline from the fuel rail. latch clip will not fit, this indicates the fuel line After disconnection, the locking fingers will remain is not properly installed to the fuel rail. Re-within the quick-connect fitting at the end of the fuel check the fuel line connection.line. (14) Connect negative battery cable to battery. (9) Inspect fuel line fitting, locking fingers and fuel (15) Start engine and check for leaks.rail fitting for damage. Replace as necessary. (10) Prior to connecting the fuel line to the fuelrail, check condition of both fittings. Clean the partswith a lint-free cloth. Lubricate them with clean en-gine oil.
14 - 12 FUEL TANKS ZJ FUEL TANKS INDEX page pageFuel Gauge Sending Unit . . . . . .. . . . . . . . . . . . . 14 Fuel Tank Pressure Relief/Rollover Valve . . . . . . . . 14Fuel Pump—Removal/Installation . . . . . . . . . . . . . 14 General Information . . . . . . . . . . . . . . . . . . . . . . . 12Fuel Tank . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 12 Heat Shields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Fuel Tank Capacities . . . . . . . . . .. . . . . . . . . . . . . 12 No-Lead Fuel Tank Filler Tube . . . . . . . . . . . . . . . . 12Fuel Tank Filler Tube Cap . . . . . .. . . . . . . . . . . . . 12GENERAL INFORMATION A label is attached to the instrument panel under These vehicles pass a full 360 degree rollover test the fuel gauge that reads UNLEADED FUEL ONLYwithout fuel leakage. To accomplish this, fuel and va- as a reminder to the driver. A similar label is locatedpor flow controls are required for all fuel tank con- near the fuel tank filler.nections. All models are equipped with a pressure relief/roll- FUEL TANK FILLER TUBE CAPover valve mounted in the top of the fuel pump mod- The loss of any fuel or vapor out of the filler neckule. is prevented by the use of a safety filler cap. This An evaporative control system prevents raw fuel will release only under pressure of 10.9 to 13.45 kPavapor from escaping into the atmosphere. Fuel va- (1.58 to 1.95 psi). The vacuum release is between .97pors from the fuel tank are collected in the EVAP and 2.0 kPa (.14 and .29 psi). This cap must be re-canister. When the engine is operating, the vapors placed by a similar unit if replacement is necessary.are drawn into the intake manifold to be used incombustion. Refer to Group 25, Emission Control CAUTION: Remove fuel tank filler tube cap prior toSystem for more information. removing or repairing fuel lines to relieve fuel tank Inspect all hose/tube connections for completeness. pressure.Be sure that leaks are not present. Replace any hosethat is cracked, scuffed, swelled, has rubbed againstother vehicle components or shows any other sign of HEAT SHIELDSwear that could lead to failure. If it is necessary to The sheet metal heat shields may have to be re-replace a hose, only hose marked EFM/EFI may be moved when servicing the fuel tank, fuel lines or va-used. por vent line. The heat shields must be installed to When installing hoses, be sure that they are routed protect the lines and tank from the heat of the ex-away from contact with other vehicle components. haust system. Refer to Group 11, Exhaust System The hose clamps used on fuel injected vehicles are and Intake Manifold for proper installation.of a special rolled edge construction to prevent theedge of the clamp from cutting into the hose. Only FUEL TANK CAPACITIESthese rolled edge type clamps may be used on this Refer to the Specifications section at the end of thesystem. Other types of clamps may cut into the hoses Fuel System Group.and cause high-pressure fuel leaks.NO-LEAD FUEL TANK FILLER TUBE FUEL TANK These vehicles are designed to operate using Un- WARNING: THE FUEL SYSTEM IS UNDER CON-leaded fuels. The diameter of the opening in the fuel STANT FUEL PRESSURE EVEN WITH THE ENGINEtank filler neck is sized to only accept unleaded fuel OFF. THIS PRESSURE MUST BE RELEASED BE-nozzles. Gasoline station pumps for unleaded and FORE SERVICING FUEL TANK.leaded fuels have different size nozzles. Leaded fuelnozzles are larger in diameter than unleaded nozzles.The fuel tank filler neck opening is also equipped REMOVALwith a deflector, which the smaller unleaded nozzle (1) Disconnect negative battery cable at battery.pushes back upon entering the filler neck. The deflec- (2) Release fuel system pressure. Refer to the Fueltor will prevent the larger diameter leaded fuel noz- System Pressure Release Procedure in the Fuel De-zles from entering the filler neck and will deflect fuel livery section of this group.away from the filler neck. This happens if filling of (3) Raise and support vehicle.the tank with leaded fuel is attempted.
ZJ FUEL TANKS 14 - 13 (4) Remove the fuel tank filler hose and vent hoseretaining clamps (Fig. 1). Remove both tubes at fuelfiller tube (Fig. 1). Fig. 1 Fuel Filler Tube and Hoses (5) Remove the rear tow hooks (if equipped). (6) Remove the fuel tank skid plate mounting nuts/ Fig. 2 Fuel Tank Mountingbolts and remove skid plate (Fig. 2) (if equipped). (13) Carefully lower right side of tank while feed- (7) Remove the optional trailer hitch (if equipped). ing fuel hoses through access hole in body (Fig. 2) (8) Remove the exhaust tailpipe heat shield mount- until fuel tank filler hose clamps can be removed.ing bolts and remove shield. (14) Before removing fuel filler hoses (Fig. 2) from tank, mark their rotational position in relation toCAUTION: To protect the fuel tank from exhaust tank. Remove both hose clamps and hoses at tankheat, this shield must reinstalled after tank installa- (Fig. 2). Insert the drain hose (from an approved gas-tion. oline draining station) into either of the hose open- ings. Drain tank until empty. (9) Place a hydraulic jack to bottom of fuel tank. (15) Continue lowering tank and remove from ve- hicle.WARNING: PLACE A SHOP TOWEL AROUND FUEL (16) If tank is to be replaced, disconnect fuel tankLINES TO CATCH ANY EXCESS FUEL. pressure relief/rollover valve (Fig. 2) from tank. For valve removal, refer to Fuel Tank Pressure Relief/ (10) Disconnect fuel supply line at inlet side of fuel Rollover Valve in this section. Remove fuel pumpfilter. Disconnect fuel vent line near front of tank. module from tank. Refer to Fuel Pump Module Re-Refer to Fuel Tubes/Lines/Hoses and Clamps in this moval/Installation in the Fuel Delivery section of thisgroup. Also refer to Quick-Connect Fittings for proce- group.dures. (11) Disconnect fuel pump module electrical con- INSTALLATIONnector near front of tank. (1) Install fuel pump module and pressure relief/ rollover valve to tank (if removed).CAUTION: The right (passenger side) of the fuel (2) Connect the fuel filter-to-fuel pump moduletank must be lowered first to gain access to the two supply line to the fuel pump module. Refer to Fuelfuel filler hose clamps located on the left side of Tubes/Lines/Hoses and Clamps in this group. Also re-tank (Fig. 2). fer to Quick-Connect Fittings for procedures. (3) Install fuel filler hoses and hose clamps (Fig. 2) (12) Remove the two fuel tank strap nuts (Fig. 2). to tank noting their previously marked position.Position both tank support straps away from tank. (4) Position fuel tank to hydraulic jack.
14 - 14 FUEL TANKS ZJ (5) Raise tank into position while guiding the fuelfiller hoses into and through the access hole (Fig. 2)in body. (6) Continue raising tank until positioned to body. (7) Attach two fuel tank mounting straps andmounting nuts.CAUTION: The two mounting nuts must be tight-ened until 80 mm (3.149 in.) is attained between theend of the mounting bolt and bottom of strap. Seeinsert (Fig. 2). Do not over tighten nuts. (8) Connect pump module electrical connector. (9) Install exhaust tailpipe heat shield. (10) Connect the fuel filter-to-fuel pump modulesupply line to the fuel filter. Refer to Fuel Tubes/Lines/Hoses and Clamps in this group. Also refer to Fig. 3 Pressure Relief/Rollover Valve LocationQuick-Connect Fittings for procedures. (11) Install the fuel tank skid plate (Fig. 2) andtrailer hitch (if equipped). (12) Install the rear tow hooks (if equipped). (13) Install the fuel tank filler hose and vent hoseto tank necks. Tighten both retaining clamps (Fig. 1). (14) Lower vehicle and connect battery cable tobattery.FUEL PUMP—REMOVAL/INSTALLATION The electric fuel pump is not serviceable. If itneeds replacement, the complete fuel pump modulemust be replaced. Refer to Fuel Pump Module in theFuel Delivery System section of this group.FUEL GAUGE SENDING UNIT The fuel gauge sending unit is not serviceable. If itneeds replacement, the complete fuel pump modulemust be replaced. Refer to Fuel Pump Module in theFuel Delivery System section of this group.FUEL TANK PRESSURE RELIEF/ROLLOVER VALVE The fuel tank is equipped with a pressure relief/ Fig. 4 Pressure Relief/Rollover Valve Operationrollover valve (Fig. 3). The dual function valve will REMOVALrelieve fuel tank pressure and prevent fuel flow (1) Disconnect negative battery cable.through the fuel tank vent tubes in the event of ac- (2) Drain and remove the fuel tank. Refer to Fuelcidental vehicle rollover. Tank removal and installation in the Fuel Tank sec- The valve consists of a plunger, spring and orifice/ tion of this group.guide plate (Fig. 4). The valve is normally open al- (3) The valve is seated in a grommet. Remove bylowing fuel vapor to vent to the EVAP canister. Here prying one side upward and then roll the grommetit is stored until it can be consumed by the engine out of tank.(under controlled conditions). The plunger seats inthe guide plate at the orifice preventing liquid fuel INSTALLATIONfrom reaching the EVAP canister. This is done if bot- (1) Start one side of grommet into opening in fueltom of plunger is contacted by fuel sloshing in tank tank. Using finger pressure only, press valve/grom-when vehicle is cornering. met into place. In the event of accidental vehicle rollover, the valve (2) Install fuel tank. Refer to Fuel Tank Installa-is inverted. In this position the plunger is forced tion.against the guide plate and raw fuel is prevented (3) Fill fuel tank. Install fuel tank filler cap.from flowing through the valve orifice into the fuel (4) Connect negative battery cable.tank vent tube. (5) Start vehicle and check for leaks.
ZJ ACCELERATOR PEDAL AND THROTTLE CABLE 14 - 15 ACCELERATOR PEDAL AND THROTTLE CABLEGENERAL INFORMATION INSTALLATION The accelerator pedal is connected to the throttle (1) Place accelerator pedal assembly over studsbody linkage by the throttle cable. The cable is pro- protruding from floor pan. Tighten mounting nuts totected by a plastic sheathing and is connected to the 10 N⅐m (92 in. lbs.) torque.throttle body linkage by a ball socket (4.0L engine) or (2) Slide throttle cable into opening in top of pedalpin (5.2L engine). It is connected to the accelerator arm. Push plastic cable retainer (clip) into pedal armpedal arm by a plastic retainer (clip) (Fig. 1). This re- opening until it snaps into place.tainer (clip) snaps into the top of the accelerator (3) Before starting engine, operate acceleratorpedal arm. Retainer tabs (built into the cable sheath- pedal to check for any binding.ing) (Fig. 1) fasten the cable to the dash panel. THROTTLE CABLE REMOVAL (1) From inside the vehicle, hold up accelerator pedal. Remove plastic cable retainer (clip) and throt- tle cable core wire from upper end of pedal arm (Fig. 1). Plastic cable retainer (clip) snaps into pedal arm. (2) Remove the cable core wire at pedal arm. (3) From inside the vehicle, pinch both sides of the cable housing retainer tabs (Fig. 1) at the dash panel. Remove cable housing from dash panel and pull into the engine compartment. (4) 4.0L Engine: Remove cable from clip on engine valve cover (Fig. 2) and clip at dash panel. Fig. 1 Accelerator Pedal Mounting—Typical Dual throttle return springs (attached to the throt-tle shaft) are used to close the throttle.CAUTION: Never attempt to remove or alter thesesprings.ACCELERATOR PEDALCAUTION: Be careful not to damage or kink the ca-ble core wire (within the cable sheathing) while ser-vicing accelerator pedal or throttle cable. Fig. 2 Throttle Cable—4.0L EngineREMOVAL (1) From inside the vehicle, hold up accelerator (5) Remove the throttle cable ball end socket atpedal. Remove plastic cable retainer (clip) and throt- throttle body linkage (Figs. 2 or 3) (snaps off).tle cable core wire from upper end of pedal arm (Fig. (6) 4.0L Engine: Remove throttle cable from throt-1). Plastic cable retainer (clip) snaps into pedal arm. tle body mounting bracket by compressing retainer (2) Remove accelerator pedal bracket nuts. Remove tabs and pushing cable through hole in bracket. Re-accelerator pedal assembly (Fig. 1). move throttle cable from vehicle.
14 - 16 ACCELERATOR PEDAL AND THROTTLE CABLE ZJ Fig. 3 Throttle Cable—5.2L V-8 Engine Fig. 4 Cable Release Tab—5.2L Engines—Typical (7) 5.2L Engine: Remove cable housing at throttle (2) 5.2L Engine: Connect cable ball end to throttlebody mounting bracket by pressing forward on re- body linkage ball (snaps on). Connect cable to throt-lease tab with a small screwdriver (Fig. 4). To pre- tle body bracket (push down and lock).vent cable housing breakage, press on the tab (3) 4.0L Engine: Snap cable into clip on engineonly enough to release the cable from the valve cover and clip at dash panel.bracket. Lift the cable housing straight up from (4) Push other end of cable through opening inbracket while pressing on release tab. Remove throt- dash panel until retaining tabs lock into panel.tle cable from vehicle. (5) From inside drivers compartment, slide throttleINSTALLATION cable core wire into opening in top of pedal arm. (1) 4.0L Engine: Slide throttle cable through hole Push cable retainer (clip) into pedal arm opening un-in throttle body bracket until retainer tabs lock into til it snaps in place.bracket. Connect cable ball end to throttle body link- (6) Before starting engine, operate acceleratorage ball (snaps on). pedal to check for any binding.
ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE 14 - 17 MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 CYL. ENGINE—COMPONENT DESCRIPTION/SYSTEM OPERATION INDEX page pageAir Conditioning (A/C) Clutch Relay—PCM Output . 23 Intake Manifold Air Temperature Sensor—PCMAir Conditioning (A/C) Controls—PCM Input . . . . . . 19 Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Auto Shutdown (ASD) Relay—PCM Output . . . . . . 23 Malfunction Indicator Lamp—PCM Output . . . . . . . 24Automatic Shutdown (ASD) Sense—PCM Input . . . 19 Manifold Absolute Pressure (MAP) Sensor—PCMBattery Voltage—PCM Input . . . . . . . . . . . . . . . . . 19 Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Brake Switch—PCM Input . . . . . . . . . . . . . . . . . . . 19 Open Loop/Closed Loop Modes of Operation . . . . . 25Camshaft Position Sensor—PCM Input . . . . . . . . . 19 Oxygen (O2S) Sensor—PCM Input . . . . . . . . . . . . 21Crankshaft Position Sensor—PCM Input . . . . . . . . 20 Park/Neutral Switch—PCM Input . . . . . . . . . . . . . . 21Data Link Connector—PCM Input . . . . . . . . . . . . . 19 Power Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Data Link Connector—PCM Output . . . . . . . . . . . . 24 Powertrain Control Module (PCM) . . . . . . . . . . . . . 18Duty Cycle Evap Purge Solenoid—PCM Output . . . 24Engine Coolant Temperature Sensor—PCM Input . 21 SCI Receive—PCM Input . . . . . . . . . . . . . . . . . . . 22Fuel Injectors—PCM Output . . . . . . . . . . . . . . . . . 24 SCI Transmit—PCM Output . . . . . . . . . . . . . . . . . . 25Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 28 Sensor Return—PCM Input . . . . . . . . . . . . . . . . . . 22Fuel Rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Shift Indicator—PCM Output . . . . . . . . . . . . . . . . . 25General Information . . . . . . . . . . . . . . . . . . . . . . . 17 Speed Control—PCM Input . . . . . . . . . . . . . . . . . . 22Generator Field—PCM Output . . . . . . . . . . . . . . . . 24 Speed Control—PCM Output . . . . . . . . . . . . . . . . . 25Generator Lamp—PCM Output . . . . . . . . . . . . . . . 24 Tachometer—PCM Output . . . . . . . . . . . . . . . . . . . 25Idle Air Control (IAC) Motor—PCM Output . . . . . . . 23 Throttle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Ignition Circuit Sense—PCM Input . . . . . . . . . . . . . 21 Throttle Position Sensor (TPS)—PCM Input . . . . . . 22Ignition Coil—PCM Output . . . . . . . . . . . . . . . . . . . 25 Vehicle Speed Sensor—PCM Input . . . . . . . . . . . . 22GENERAL INFORMATION specific sequence by the PCM. The PCM maintains All 4.0L engines are equipped with sequential an air/fuel ratio of 14.7 to 1 by constantly adjustingMulti-Port Fuel Injection (MFI). The MFI system injector pulse width. Injector pulse width is theprovides precise air/fuel ratios for all driving condi- length of time that the injector opens and sprays fueltions. into the chamber. The PCM adjusts injector pulse The powertrain control module (PCM) operates the width by opening and closing the ground path to thefuel system. The PCM was formerly referred to as injector.the SBEC or engine controller. The PCM is a pre-pro- Manifold absolute pressure (air density) and enginegrammed, dual microprocessor digital computer. It rpm (speed) are the primary inputs that determineregulates ignition timing, air-fuel ratio, emission con- fuel injector pulse width. The PCM also monitorstrol devices, charging system, speed control, air con- other inputs when adjusting air-fuel ratio.ditioning compressor clutch engagement and idle Inputs That Effect Fuel Injector Pulse Width:speed. The PCM can adapt its programming to meet • Exhaust gas oxygen contentchanging operating conditions. • Engine coolant temperature Powertrain Control Module (PCM) Inputs rep- • Manifold absolute pressure (MAP)resent the instantaneous engine operating conditions. • Engine speedAir-fuel mixture and ignition timing calibrations for • Throttle positionvarious driving and atmospheric conditions are pre- • Battery voltageprogrammed into the PCM. The PCM monitors and • Air conditioning selectionanalyzes various inputs. It then computes engine fuel • Transmission gear selection (automatic transmis-and ignition timing requirements based on these in- sions only)puts. Fuel delivery control and ignition timing will • Speed controlthen be adjusted accordingly. The powertrain control module (PCM) adjusts igni- Other inputs to the PCM are provided by the brake tion timing by controlling ignition coil operation. Thelight switch, air conditioning select switch and the ignition coil receives battery voltage when the igni-speed control switches. All inputs to the PCM are tion key is in the run or starter position. The PCMconverted into signals. provides a ground for the ignition coil. The coil dis- Electrically operated fuel injectors spray fuel in charges when the PCM supplies a ground. By switch-precise metered amounts into the intake port directly ing the ground path on and off, the PCM regulatesabove the intake valve. The injectors are fired in a ignition timing.
14 - 18 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE ZJ The sensors and switches that provide inputs to The PCM adjusts ignition timing based upon in-the powertrain control module (PCM) comprise the puts it receives from sensors that react to: engineEngine Control System. It is also comprised of the rpm, manifold absolute pressure, engine coolant tem-PCM Outputs (engine control devices that the are op- perature, throttle position, transmission gear selec-erated by the PCM). tion (automatic transmission), vehicle speed and the brake switch.SYSTEM DIAGNOSIS The PCM adjusts idle speed based on inputs it re- The powertrain control module (PCM) tests many ceives from sensors that react to: throttle position,of its own input and output circuits. If a Diagnostic vehicle speed, transmission gear selection, engineTrouble Code (DTC) is found in a major system, this coolant temperature and from inputs it receives frominformation is stored in the PCM memory. Refer to the air conditioning clutch switch and brake switch.On-Board Diagnostics in the MFI System—4.0L En- Based on inputs that it receives, the PCM adjustsgine—General Diagnosis section of this group for ignition coil dwell. The PCM also adjusts the gener-DTC information. ator charge rate through control of the generator field and provides speed control operation.POWERTRAIN CONTROL MODULE (PCM) Powertrain Control Module (PCM) Inputs: The powertrain control module (PCM) (Fig. 1) oper- • Generator outputates the fuel system. The PCM was formerly referred • A/C request (if equipped with factory A/C)to as the SBEC or engine controller. The PCM is a • A/C select (if equipped with factory A/C)pre-programmed, dual microprocessor digital com- • Auto shutdown (ASD) senseputer. It regulates ignition timing, air-fuel ratio, • Intake manifold air temperature sensoremission control devices, charging system, speed con- • Battery voltagetrol, air conditioning compressor clutch engagement • Brake switchand idle speed. The PCM can adapt its programming • Engine coolant temperature sensorto meet changing operating conditions. • Crankshaft position sensor • Ignition circuit sense (ignition switch in run posi- tion) • Manifold absolute pressure sensor • Overdrive/override switch • Oxygen sensor • Park/neutral switch (auto. trans. only) • SCI receive (DRB scan tool connection) • Speed control resume switch • Speed control set switch • Speed control on/off switch • Camshaft position sensor signal • Throttle position sensor • Vehicle speed sensor • Sensor return • Power ground • Signal ground Powertrain Control Module (PCM) Outputs: • A/C clutch relay • Idle air control (IAC) motor • Auto shutdown (ASD) relay • Generator field • Malfunction indicator lamp (Check engine lamp) Fig. 1 Powertrain Control Module (PCM) • Fuel injectors • Fuel pump relay The PCM receives input signals from various • Ignition coilswitches and sensors. Based on these inputs, the • SCI transmit (DRB scan tool connection)PCM regulates various engine and vehicle operations • Shift indicator lamp (manual transmission only)through different system components. These compo- • Speed control vacuum solenoidnents are referred to as powertrain control module • Speed control vent solenoid(PCM) outputs. The sensors and switches that pro- • Tachometer (on instrument panel, if equipped)vide inputs to the PCM are considered powertrain The powertrain control module (PCM) contains acontrol module (PCM) inputs. voltage convertor. This converts battery voltage to a
ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE 14 - 19regulated 8.0 volts. It is used to power the crankshaft If battery voltage is low, the PCM will increase in-position sensor, camshaft position sensor and vehicle jector pulse width (period of time that the injector isspeed sensor. The PCM also provides a five (5) volt energized). This is done to compensate for the re-supply for the manifold absolute pressure (MAP) sen- duced flow through the injector caused by the low-sor and throttle position sensor (TPS). ered voltage.AIR CONDITIONING (A/C) CONTROLS—PCM INPUT BRAKE SWITCH—PCM INPUT The A/C control system information applies to fac- When the brake light switch is activated, the pow-tory installed air conditioning units. ertrain control module (PCM) receives an input indi- A/C SELECT SIGNAL: When the A/C switch is in cating that the brakes are being applied. Afterthe ON position and the A/C low-pressure switch is receiving this input, the PCM maintains idle speed toclosed, an input signal is sent to the powertrain con- a scheduled rpm through control of the idle air con-trol module (PCM). The signal informs the PCM that trol (IAC) motor. The brake switch input is also usedA/C has been selected. The PCM then adjusts idle to operate the speed control system.speed to a pre-programmed rpm through the idle aircontrol (IAC) motor to compensate for increased en- CAMSHAFT POSITION SENSOR—PCM INPUTgine load. A sync signal is provided by the camshaft position sensor located in the distributor (Fig. 2). The sync A/C REQUEST SIGNAL: Once A/C has been se- signal from this sensor works in conjunction with thelected, the powertrain control module (PCM) receives crankshaft position sensor to provide the powertrainthe A/C request signal from the evaporator switch. control module (PCM) with inputs. This is done to es-The input indicates that the evaporator temperature tablish and maintain correct injector firing order.is in the proper range for A/C application. The PCM Refer to Camshaft Position Sensor in Group 8D, Ig-uses this input to cycle the A/C compressor clutch nition System for more information.through the A/C relay. It will also determine the cor-rect engine idle speed through the idle air control(IAC) motor position. If the A/C low-pressure switch opens (indicating alow refrigerant level), the PCM will not receive anA/C select signal. The PCM will then remove theground from the A/C relay. This will deactivate theA/C compressor clutch. If the evaporator switch opens, indicating thatevaporator is not in proper temperature range, thePCM will not receive the A/C request signal. ThePCM will then remove the ground from the A/C relay,deactivating the A/C compressor clutch.AUTOMATIC SHUTDOWN (ASD) SENSE—PCMINPUT A 12 volt signal at this input indicates to the PCM Fig. 2 Camshaft Position Sensor—Typicalthat the ASD has been activated. The ASD relay islocated in the power distribution center (PDC) in the DATA LINK CONNECTOR—PCM INPUTengine compartment. It is used to connect the oxygen The data link connector (diagnostic scan tool con-sensor heater element, ignition coil, generator field nector) links the DRB scan tool with the powertrainwinding and fuel injectors to 12 volt + power supply. control module (PCM). The data link connector is lo- This input is used only to sense that the ASD relay cated in the engine compartment (Fig. 3). For opera-is energized. If the powertrain control module (PCM) tion of the DRB scan tool, refer to the appropriatedoes not see 12 volts at this input when the ASD Powertrain Diagnostic Procedures service manual.should be activated, it will set a Diagnostic Trouble The data link connector uses two different pins onCode (DTC). the PCM. One is for Data Link Transmit and the other is for Data Link Receive.BATTERY VOLTAGE—PCM INPUT The battery voltage input provides power to the INTAKE MANIFOLD AIR TEMPERATURE SENSOR—powertrain control module (PCM). It also informs the PCM INPUTPCM what voltage level is supplied to the ignition The intake manifold air temperature sensor is in-coil and fuel injectors. stalled in the intake manifold with the sensor ele-
14 - 20 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE ZJ sor signal, is used to differentiate between fuel injec- tion and spark events. It is also used to synchronize the fuel injectors with their respective cylinders. The sensor is bolted to the transmission housing near the rear of the cylinder head (Figs. 5 or 6). Fig. 3 Data Link Connector Location—Typical Fig. 5 Crankshaft Position Sensor—4.0L Enginement extending into the air stream (Fig. 4). The With Man. Trans.sensor provides an input voltage to the powertraincontrol module (PCM) indicating intake manifold airtemperature. The input is used along with inputsfrom other sensors to determine injector pulse width.As the temperature of the air-fuel stream in themanifold varies, the sensor resistance changes. Thisresults in a different input voltage to the PCM. Fig. 6 Crankshaft Position Sensor—4.0L Engine Fig. 4 Air Temperature Sensor With Auto. Trans.CRANKSHAFT POSITION SENSOR—PCM INPUT Refer to Group 8D, Ignition System for more crank- This sensor is a hall effect device that detects shaft position sensor information.notches in the flywheel (manual transmission), or The engine will not operate if the PCM does not re-flexplate (automatic transmission). ceive a crankshaft position sensor input. This sensor is used to indicate to the powertraincontrol module (PCM) that a spark and or fuel injec-tion event is to be required. The output from thissensor, in conjunction with the camshaft position sen-
ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE 14 - 21ENGINE COOLANT TEMPERATURE SENSOR—PCMINPUT The engine coolant temperature sensor is installedin the thermostat housing (Fig. 7) and protrudes intothe water jacket. The sensor provides an input volt-age to the powertrain control module (PCM) relatingengine coolant temperature. The PCM uses this in-put along with inputs from other sensors to deter-mine injector pulse width and ignition timing. Ascoolant temperature varies, the coolant temperaturesensor’s resistance changes. The change in resistanceresults in a different input voltage to the PCM. When the engine is cold, the PCM will operate inOpen Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is doneuntil normal operating temperatures are reached. Fig. 8 Manifold Absolute Pressure (MAP) Sensor OXYGEN (O2S) SENSOR—PCM INPUT The O2S sensor is located in the exhaust down pipe (Fig. 9). It provides an input voltage to the power- train control module (PCM) relating the oxygen con- tent of the exhaust gas. The PCM uses this information to fine tune the air-fuel ratio by adjust- ing injector pulse width. The O2S sensor produces voltages from 0 to 1 volt. This voltage will depend upon the oxygen content of the exhaust gas in the exhaust manifold. When a large amount of oxygen is present (caused by a lean air-fuel mixture), the sensor produces a low voltage. When there is a lesser amount present (rich air-fuel mixture) it produces a higher voltage. By monitoring the oxygen content and converting it to electrical Fig. 7 Coolant Temperature Sensor voltage, the sensor acts as a rich-lean switch. The oxygen sensor is equipped with a heating ele-IGNITION CIRCUIT SENSE—PCM INPUT ment that keeps the sensor at proper operating tem- The ignition circuit sense input tells the powertrain perature during all operating modes. Maintainingcontrol module (PCM) the ignition switch has ener- correct sensor temperature at all times allows thegized the ignition circuit. Refer to the wiring dia- system to enter into closed loop operation sooner.grams for circuit information. In Closed Loop operation, the powertrain control module (PCM) monitors the O2S sensor input (alongMANIFOLD ABSOLUTE PRESSURE (MAP) with other inputs). It then adjusts the injector pulseSENSOR—PCM INPUT width accordingly. During Open Loop operation, the The MAP sensor reacts to absolute pressure in the PCM ignores the O2S sensor input and adjusts injec-intake manifold. It provides an input voltage to the tor pulse width to a preprogrammed value (based onpowertrain control module (PCM). As engine load other sensor inputs).changes, manifold pressure varies. The change inmanifold pressure causes MAP sensor voltage to PARK/NEUTRAL SWITCH—PCM INPUTchange. The change in MAP sensor voltage results in The park/neutral switch is located on the transmis-a different input voltage to the PCM. The input volt- sion housing and provides an input to the powertrainage level supplies the PCM with information about control module (PCM). This will indicate that the au-ambient barometric pressure during engine start-up tomatic transmission is in Park, Neutral or a drive(cranking) and engine load while the engine is run- gear selection. This input is used to determine idlening. The PCM uses this input along with inputs speed (varying with gear selection), fuel injectorfrom other sensors to adjust air-fuel mixture. pulse width, ignition timing advance and vehicle The MAP sensor is mounted on the dash panel speed control operation. Refer to Group 21, Transmis-(Fig. 8). The sensor is connected to the throttle body sions, for testing, replacement and adjustment infor-with a vacuum hose and to the PCM electrically. mation.
14 - 22 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE ZJ THROTTLE POSITION SENSOR (TPS)—PCM INPUT The throttle position sensor (TPS) is mounted on the throttle body (Fig. 10). The TPS is a variable re- sistor that provides the powertrain control module (PCM) with an input signal (voltage) that represents throttle blade position. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance of the TPS changes. The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from 1 volt at minimum throttle opening (idle), to 4 volts at wide open throttle. Along with inputs from other sensors, Fig. 9 Heated Oxygen Sensor Location the PCM uses the TPS input to determine current engine operating conditions. In response to enginePOWER GROUND operating conditions, the PCM will adjust fuel injec- The power ground is used to control ground circuits tor pulse width and ignition timing.for the following powertrain control module (PCM)loads:• Generator Field Winding• 8 volt (PCM) power supply• Fuel Injectors• Ignition CoilSCI RECEIVE—PCM INPUT SCI Receive is the serial data communication re-ceive circuit for the DRB scan tool. The powertraincontrol module (PCM) receives data from the DRBthrough the SCI Receive circuit.SPEED CONTROL—PCM INPUT The speed control system provides three separateinputs to the powertrain control module (PCM); On/Off, Set and Resume. The On/Off input informs the Fig. 10 Throttle Position Sensor and IAC MotorPCM that the speed control system has been acti-vated. The Set input informs the PCM that a fixed VEHICLE SPEED SENSOR—PCM INPUTvehicle speed has been selected. The Resume input The speed sensor (Fig. 11) is located in the exten-indicates to the PCM that the previous fixed speed is sion housing of the transmission (2WD) or on therequested. transfer case extension housing (4WD). The sensor The speed control operating range is from 50 km/h input is used by the powertrain control moduleto 142 km/h (35 to 85 mph). Inputs that effect speed (PCM) to determine vehicle speed and distance trav-control operation are: eled.• Brake switch position The speed sensor generates 8 pulses per sensor• Park/neutral switch revolution. These signals, in conjunction with a• Vehicle speed sensor closed throttle signal from the throttle position sen-• Throttle position sensor sor, indicate a closed throttle deceleration to the Refer to Group 8H for further speed control infor- PCM. When the vehicle is stopped at idle, a closedmation. throttle signal is received by the PCM (but a speed sensor signal is not received).SENSOR RETURN—PCM INPUT Under deceleration conditions, the PCM adjusts the Sensor Return provides a low noise ground refer- idle air control (IAC) motor to maintain a desiredence for all system sensors. MAP value. Under idle conditions, the PCM adjusts the IAC motor to maintain a desired engine speed.
ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE 14 - 23 When the PCM receives a request for A/C from the A/C evaporator switch, it will adjust idle air control (IAC) motor position. This is done to increase idle speed. The PCM will then activate the A/C clutch through the A/C clutch relay. The PCM then adjusts the idle air control (IAC) stepper motor position to compensate for increased engine load from the A/C compressor. By switching the ground path for the relay on and off, the PCM is able to cycle the A/C compressor clutch. This is based on changes in engine operating conditions. If, during A/C operation, the PCM senses low idle speeds or a wide open throttle condition, it will de-energize the relay. This prevents A/C clutch engagement. The relay will remain de-energized until the idle speed increases or the wide open throttle condition exceeds 15 seconds, or no longer exists. The PCM will also de-energize the relay if engine coolant temperature exceeds 125°C (257°F). IDLE AIR CONTROL (IAC) MOTOR—PCM OUTPUT Fig. 11 Vehicle Speed Sensor—Typical The IAC motor is mounted on the throttle body (Fig. 10) and is controlled by the powertrain controlAIR CONDITIONING (A/C) CLUTCH RELAY—PCM module (PCM).OUTPUT The throttle body has an air control passage that The powertrain control module (PCM) activates the provides air for the engine at idle (the throttle plateA/C compressor through the A/C clutch relay. The is closed). The IAC motor pintle protrudes into thePCM regulates A/C compressor operation by switch- air control passage and regulates air flow through it.ing the ground circuit for the A/C clutch relay on and Based on various sensor inputs, the powertrain con-off. The relay is located in the power distribution trol module (PCM) adjusts engine idle speed by mov-center (PDC) (Fig. 12). For the location of the relay ing the IAC motor pintle in and out of the air controlwithin the PDC, refer to label under PDC cover. passage. The IAC motor is positioned when the igni- tion key is turned to the On position. A (factory adjusted) set screw is used to mechani- cally limit the position of the throttle body throttle plate. Never attempt to adjust the engine idle speed using this screw. All idle speed functions are controlled by the PCM. AUTO SHUTDOWN (ASD) RELAY—PCM OUTPUT The ASD relay is located in the power distribution center (PDC) (Fig. 12). For the location of this relay within the PDC, refer to label under PDC cover. The ASD supplies battery voltage to the fuel pump, fuel injector, ignition coil, generator field winding and oxygen (O2S) sensor heating element. The ground circuit for the coil in the ASD relay is con- trolled by the powertrain control module (PCM). The PCM operates the relay by switching the ground cir- cuit on and off. The fuel pump relay is controlled by the PCM through same circuit that the ASD relay is con- trolled. Fig. 12 Power Distribution Center (PDC)