PRELIMINARY INSPECTION & ADJUSTMENTS

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1 PRELIMINARY INSPECTION & ADJUSTMENTS VISUAL INSPECTION Most driveability problems in the engine control system result from faulty wiring, poor electrical connections or leaking air and vacuum hose connections. To avoid unnecessary component testing, perform a visual inspection before beginning self-diagnostic tests. Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not cracked, pinched or cut. See VACUUM DIAGRAMS article. Inspect air induction system for possible vacuum leaks. MECHANICAL INSPECTION Check engine mechanical condition with a compression gauge, vacuum gauge or scan tool. See scan tool manual for specific instructions. Compression WARNING: DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine. Fuel injectors are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine's oiling system. Ensure battery is fully charged and starter motor is in good operating condition. On 2.5L, disconnect ignition coil connector. On 4.0L, remove coil rail assembly to access spark plugs. On 4.7L, remove coil on plugs. On all models, clean spark plug recesses with compressed air. Remove all spark plugs. Remove fuel pump relay from power distribution center. See Fig. 1, Fig. 2 or Fig. 3. Install compression gauge. Hold throttle in Wide Open Throttle (WOT) position. Using a remote starter switch, rotate engine 3 revolutions. Record compression pressure from third revolution. Continue test for remaining cylinders. See COMPRESSION SPECIFICATIONS table for correct engine compression pressures. COMPRESSION SPECIFICATIONS Application psi (kg/cm 2 ) Normal Compression Pressure 2.5L & 4.0L ( ) 4.7L ( ) Maximum Variation Between Cylinders 2.5L & 4.0L 30 (2.1) 4.7L (1) (1) Information is not available from manufacturer.

2 Fig. 1: Identifying Power Distribution Center (Cherokee) Courtesy of DAIMLERCHRYSLER CORPORATION

3 Fig. 2: Identifying Power Distribution Center (Grand Cherokee) Courtesy of DAIMLERCHRYSLER CORPORATION Fig. 3: Identifying Power Distribution Center (Wrangler) Courtesy of DAIMLERCHRYSLER CORPORATION CHECKING ENGINE VACUUM NOTE: Normal vacuum readings vary according to altitude. Connect vacuum gauge to engine vacuum source. Start engine and allow engine to idle. Note engine vacuum reading. Engine vacuum should be steady and in. Hg with engine at idle. While monitoring engine vacuum reading, quickly open and close the throttle several times and then allow engine to idle. If engine vacuum is within specification, test is complete. If engine vacuum is not within specification, check for vacuum leaks and repair as necessary. If no vacuum leaks are found, check for engine mechanical problem. FUEL SYSTEMS WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel injectionrelated component. DO NOT allow fuel to contact engine or electrical components. CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

4 Basic diagnosis of fuel system should begin with determining fuel system pressure. FUEL SYSTEM PRESSURE RELEASE WARNING: Fuel system is under high pressure. ALWAYS release fuel pressure before attempting to open system for testing or component replacement. DO NOT allow fuel to flow onto engine or electrical parts while testing fuel system components. 1. Remove fuel pump relay from Power Distribution Center (PDC). PDC is located in right side of engine compartment, next to battery. See Fig. 1, Fig. 2 or Fig. 3. Start and run engine until it stalls. Attempt to start engine. Continue restarting engine until it will no longer run. Turn ignition off. NOTE: One or more Diagnostic Trouble Codes (DTC) may set when fuel pump relay is removed. 2. Disconnect any fuel injector connector. Connect a jumper wire between either fuel injector terminal and positive battery terminal. Connect another jumper wire to other fuel injector terminal. Momentarily touch other end of jumper wire to negative battery terminal. CAUTION: DO NOT supply power to fuel injector for more than 4 seconds, or fuel injector may be damaged. 3. Place a shop towel under fuel line quick-connector at fuel rail. Use care when disconnecting fuel lines, as some fuel pressure may still exist in fuel lines. Disconnect fuel line quick-connector at fuel rail. Reinstall fuel pump relay in PDC. Reconnect fuel line quick-connector. Using scan tool, erase any DTCs that may have set after fuel pressure release procedure. FUEL PRESSURE TEST Cherokee & Wrangler NOTE: Cherokee and Wrangler models are equipped with a mechanical fuel pressure regulator located in top of fuel tank. Excess fuel is returned to tank through fuel pressure regulator. 1. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE. Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. 2. Start engine and allow to idle. Fuel pressure should be psi ( kg/cm 2 ). If no fuel pressure exists, fuel pump relay control circuit may be defective. See DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article. 3. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, go to FUEL PUMP VOLUME TEST.

5 4. If fuel pressure is more than specified, fuel pump is okay, but fuel pressure regulator is defective. Release fuel pressure and replace fuel pressure regulator. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. 5. If fuel pressure is as specified, release fuel pressure. Remove test gauge hose. Install test port cap. Grand Cherokee NOTE: Grand Cherokee is equipped with a mechanical fuel pressure regulator. Fuel filter/pressure regulator is located in front of fuel tank, above rear axle. See Fig. 4. Excess fuel is returned to tank through fuel return line and fuel pressure regulator. 1. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE. Remove test port cap. Install a 0-60 psi (0-4.2 kg/cm 2 ) fuel pressure gauge at test port. 2. Start engine and allow it to idle. Fuel pressure should be psi ( kg/cm 2 ). If no fuel pressure exists, fuel pump relay control circuit may be defective. See DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - GRAND CHEROKEE article. WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL SYSTEM PRESSURE RELEASE. 3. If fuel pressure is less than specified, go to next step. If fuel pressure is more than specified, check fuel return line for kinks or restrictions. See Fig. 4. Repair fuel return line as necessary. If fuel return line is okay, replace fuel filter/pressure regulator. If fuel pressure is as specified, fuel system is okay. Diagnose by symptom. See TROUBLE SHOOTING - NO CODES article. 4. If engine runs but fuel pressure is less than specified, check for kinked or damaged fuel supply line between fuel pump module and fuel rail. Repair fuel line as necessary and retest. If fuel line is okay, release fuel pressure. Raise and support vehicle. Disconnect fuel pressure line from fuel filter/pressure regulator. See Fig. 4. Connect Fuel Line Pressure Test Adapter Hose (6539) between disconnected fuel line and fuel filter/pressure regulator. Connect fuel pressure gauge to fuel line adapter hose. Turn ignition on, with engine off. Using scan tool, actuate ASD fuel system test and note fuel pressure. Fuel pressure should be psi ( kg/cm 2 ). If fuel pressure is within specification, stop ASD fuel system activation, release fuel pressure and replace fuel filter/pressure regulator. If fuel pressure is not within specification, stop ASD fuel system activation, release fuel pressure and replace fuel pump module.

6 Fig. 4: Locating Fuel Filter/Pressure Regulator (Grand Cherokee) Courtesy of DAIMLERCHRYSLER CORPORATION FUEL PUMP AMPERAGE TEST Cherokee 1. Perform FUEL PRESSURE TEST and FUEL PUMP VOLUME TEST before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50 F (10 C). WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected. 2. Remove fuel pump relay from Power Distribution Center (PDC). See Fig. 1. Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal C2 (Dark Green/White wire) at fuel pump relay

7 socket in PDC. See Fig. 1. Connect positive lead of ammeter to terminal C1 (Dark Green/Black wire) at fuel pump relay socket in PDC. 3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay. Grand Cherokee 1. Perform FUEL PRESSURE TEST and FUEL PUMP VOLUME TEST before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. Ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50 F (10 C). 2. Remove fuel pump relay from Power Distribution Center (PDC). See Fig. 2. Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal No. 87 (Dark Green/Black wire) at fuel pump relay socket in PDC. See Fig. 2. Connect positive lead of ammeter to terminal No. 30 (Violet/White wire) at fuel pump relay socket in PDC. 3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay. Wrangler WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected. 1. Perform FUEL PRESSURE TEST and FUEL PUMP VOLUME TEST before performing this test. If fuel pressure and fuel volume are okay, ensure fuel tank has fuel. If fuel tank is empty or near empty, amperage readings will be incorrect. Ensure fuel tank temperature is more than 50 F (10 C). WARNING: With ammeter installed in place of fuel pump relay, fuel pump will be activated even with ignition off. Before connecting ammeter, ensure all fuel lines and fuel system components are connected. 2. Remove fuel pump relay from Power Distribution Center (PDC). See Fig. 3. Set ammeter to 10-amp scale. Connect negative lead of ammeter to terminal C9 (Dark Green/White wire) at fuel pump relay socket in PDC. See Fig. 3. Connect positive lead of ammeter to terminal C10 (Dark Green/Black wire) at fuel pump relay socket in PDC. 3. If fuel pump current draw is 10 amps or more, replace fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. If fuel pump current draw is less than 10 amps, fuel pump module is okay. FUEL PUMP VOLUME TEST 1. Perform FUEL PRESSURE TEST. If fuel pressure is okay, relieve fuel system pressure. See FUEL

8 SYSTEM PRESSURE RELEASE. Ensure area around fuel supply line and fuel rail are clean. 2. Disconnect fuel supply line from fuel rail. Install Fuel Line Pressure Test Adapter Hose (6539 for 5/16" fuel lines or 6631 for 3/8" fuel lines) between disconnected fuel line and fuel rail. Remove fuel fill cap. Insert other end of hose into a graduated container suitable for gasoline. CAUTION: DO NOT operate fuel pump longer than 7 seconds. 3. Connect scan tool to data link connector. Using scan tool, actuate fuel pump. Fuel volume should be as specified. See FUEL PUMP PERFORMANCE table. If fuel volume is not as specified, but fuel pump can be heard through fuel fill pipe, check for a kinked fuel line between fuel pump module and fuel rail. Repair fuel lines as necessary and retest. 4. If fuel line is okay and fuel pressure is okay, but volume is low, replace fuel filter/fuel pressure regulator. On Cherokee and Wrangler, fuel filter/fuel pressure regulator is located in top of fuel tank. See FUEL FILTER/FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. On Grand Cherokee, fuel filter/pressure regulator is located in front of fuel tank, above rear axle. See Fig. 4. On all models, if fuel pressure and volume are low, replace fuel pump module assembly. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION article. FUEL PUMP PERFORMANCE (1) Application Pressure - psi (kg/cm 2 ) Min. Vol. In 7 Sec. All Models ( ).5 Pt. (.25L) (1) DO NOT operate fuel pump longer than 7 seconds. FUEL PUMP CONTROL CIRCUIT Fuel Pump Relay For fuel pump relay test, see FUEL PUMP RELAY under MOTORS, RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. For fuel pump relay circuit testing, see DTC P1282: FUEL PUMP RELAY CONTROL CIRCUIT under DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.

F - BASIC TESTING Toyota Celica INTRODUCTION PRELIMINARY INSPECTION & ADJUSTMENTS VISUAL INSPECTION MECHANICAL INSPECTION

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