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.
| 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. |
FUEL PUMP VOLUME TEST
- Perform «FUEL PRESSURE TEST»(ref-12051-S38318979682000120600000). If fuel pressure is okay, relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-12051-S35450755352000120600000). Ensure area around fuel supply line and fuel rail are clean.
- 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.
- Connect scan tool to data link connector. Using scan tool, actuate fuel pump. Fuel volume should be as specified. See «FUEL PUMP PERFORMANCE»(ref-12051-S32651804082000120600000) 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.
- 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. (Схема №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.
| Application | Pressure - psi (kg/cm 2 ) | Min. Vol. In 7 Sec. |
|---|---|---|
| All Models | 44.2-54.2 (3.1-3.7) | .5 Pt. (.25L) |
| (1) DO NOT operate fuel pump longer than 7 seconds. | ||
| (1) | DO NOT operate fuel pump longer than 7 seconds. |
FUEL PUMP PERFORMANCE (1)
POWERTRAIN VERIFICATION TEST VER-1
Note. If replacing Powertrain Control Module (PCM), the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into PCM to prevent Diagnostic Trouble Codes (DTC) from being stored in Anti-Lock Brake System (ABS) module and Air Bag Control Module (ACM). If replacing PCM and vehicle is equipped with a Smart Key Immobilizer Module (SKIM), secret key data must also be updated to enable engine starting.
- Inspect vehicle to ensure all engine components are connected. Reassemble and reconnect components as necessary. If repair procedure did not include replacing PCM, go to next step. If PCM has been replaced and has already been programmed, go to next step. If PCM has been replaced but has not been programmed, program PCM and clear DTCs. See «PROGRAMMING»(ref-12051-S23258349112000120600000) . After PCM is programmed, go to next step.
- Inspect engine oil for fuel contamination. Change engine oil and filter as necessary. Attempt to start engine. If engine starts and stays running, test is complete. If engine does not start, check for related technical service bulletins. If necessary, go to TROUBLE SHOOTING - NO CODES article for additional testing.